bims-proteo 2026-03-22 papers

bims-proteo

Biomed News

on Proteostasis

Issue of 2026–03–22
38 papers selected by
Eric Chevet, INSERM

UFMylation: A Key Role in Maintaining Endoplasmic Reticulum Homeostasis.
The E3 ubiquitin ligase mechanism specifying targeted microRNA degradation.
SEL1L-HRD1 ERAD-autophagy interplay maintains mitochondrial homeostasis in brown adipocytes.
Control of lysosome function by the GTPase-activating protein TBC1D9B and its binding partner TMEM55B.
Hijacking ERAD for targeted degradation of transmembrane proteins.
Ribosome-associated quality control and related mechanisms.
ATG2A connects lipid droplets and the ER to regulate lipid storage.
ZNFX1 uses two-component ubiquitin circuitry to quarantine viral RNA.
Functional rescue of a disease-linked ERAD pathway mutation via alternative splicing.
Ca²⁺ leakage is a conserved signal for non-canonical ATG8/LC3 lipidation and membrane repair.
Retrograde Golgi-to-ER transport is regulated by diacylglycerol in Saccharomyces cerevisiae.
A PTPN23-dependent ESCRT pathway is essential for constitutive secretion in mammalian cells.
Calcium-mediated calreticulin-IRE1α interaction drives dynamic fluctuation of IRE1α activity under chronic endoplasmic reticulum stress.
Disulfide Crosslinking Induces Rapid Degradation of Arc/Arg3.1 via Hsp70-Mediated Ubiquitin Ligase Pathway.
Bip1 regulates AMPK signaling in response to endoplasmic reticulum stress.
An RGLG E3 Ubiquitin Ligase CaSIRE1 Negatively Regulates ABA-Dependent Drought Tolerance by Destabilizing CaSAP14 in Pepper.
Small heat shock proteins HspB1 and HspB5 differentially alter the condensation and aggregation of the TDP-43 low-complexity domain.
PERK Deficiency Amplifies Molecular, Structural, and Network Vulnerability to Repetitive Mild Traumatic Brain Injury.
An RNA structural switch controlling bacterial toxin translation.
Hierarchical membrane-chromatin tethering buffers nuclear envelope assembly against alterations in lipid flux.
Targeting ubiquitin signaling vulnerabilities in KEAP1-inactivated lung cancer.
Glycolipid transfer protein modulates vesicular trafficking from the endoplasmic reticulum in HeLa cells.
ER-tethering directs TREX1 penetration of a BAF-dependent barrier at micronuclei.
Degradation of G-quadruplex-binding proteins in chromatin using G4-ligand-based proteolysis-targeting chimeras.
The ubiquitin ligase CBL and Fas-associated factor 2 cooperate to regulate the innate immune response to M. tuberculosis.
Calmodulin-like protein condensates decode PAMP-induced nuclear calcium to activate plant immunity.
STIM1 and endoplasmic reticulum-plasma membrane contact sites oscillate independently of calcium-induced calcium release.
Human DHX29 detects nonoptimal codon usage to regulate mRNA stability.
β-arrestin1 orchestrates endosomal signaling to regulate translational control of circadian light entrainment.
Toward a unifying mechanistic model of eukaryotic translation initiation through integrative single-molecule, structural, and computational insights.
INSIG1/2 succination mediated by the moonlighting function of ADSL promotes lipogenesis and liver tumorigenesis.
Intrinsically disordered SERBP1 regulates translation through topology-driven G-quadruplex recognition.
Degron models: a toolbox for rapid in vivo depletion of essential proteins regulating mRNA metabolism.
Valosin-containing protein counteracts ATP-driven dissolution of FUS condensates through its ATPase activity in vitro.
FGF1 orchestrates circadian hepatic triglyceride secretion.
Identification of a druggable target that predicts postoperative Crohn's disease recurrence.
Human DEAH-box helicase 8 regulates HSF1-mediated stress response and cancer-associated pre-mRNA splicing in tumour cells.
Lysosomal phosphoinositide turnover acts upstream of RagGTPase-mTORC1 and controls muscle growth.

FASEB J. 2026 Mar 31. 40(6): e71710

UFMylation: A Key Role in Maintaining Endoplasmic Reticulum Homeostasis.

Kang Zheng, Yi Ai, Junlin Yang, Mengsheng Qiu.

UFMylation, a ubiquitin-like post-translational modification system, plays an essential role in regulating endoplasmic reticulum (ER) function. This process involves a cascade of biochemical reactions mediated by several core molecular components, including UFM1, the E1 enzyme UBA5, the E2 enzyme UFC1, the E3 enzyme UFL1, as well as the accessory proteins DDRGK1 and CDK5RAP3. During UFMylation, UFM1 undergoes maturation, activation, conjugation, and deconjugation in a dynamic process, whereas the ER-localized UFL1-DDRGK1 complex governs substrate selection and modification efficiency. The major function of UFMylation is to modulate the ER stress response, thereby balancing adaptive cellular remodeling and apoptotic signaling. Through the modification of key substrate proteins, UFMylation activates a synergistic clearance mechanism that coordinates ER-phagy with ribosome-associated quality control, thereby facilitating the removal of stalled ribosomes and damaged ER to maintain ER proteostasis and structural integrity. Dysregulation of UFMylation is frequently associated with various diseases characterized by abnormal ER function. In this review, we will describe the molecular pathways associated with ER-associated UFMylation process and then discuss its core regulatory functions within the ER and its possible involvements in several congenital human diseases.

DOI: https://doi.org/10.1096/fj.202504650RR
Nature. 2026 Mar 18.

The E3 ubiquitin ligase mechanism specifying targeted microRNA degradation.

Jakob Farnung, Elena Slobodyanyuk, Peter Y Wang, Lianne W Blodgett, Daniel H Lin, Susanne von Gronau, Brenda A Schulman, David P Bartel.

MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to form complexes that down-regulate target RNAs, including messenger RNAs from most human genes1-3. Within each complex, the miRNA pairs to target RNAs, and AGO provides effector function while also protecting the miRNA from cellular nucleases2-5. Although much is known about miRNA-directed gene regulation, less is known about how miRNAs themselves are regulated. One pathway that regulates miRNAs involves unusual targets called 'trigger' RNAs, which reverse the canonical regulatory logic and instead down-regulate miRNAs6-9. This target-directed miRNA degradation (TDMD) is thought to require a cullin-RING E3 ligase because it depends on the cullin protein CUL3 and other ubiquitylation components, including the BC-box protein ZSWIM8 (refs. 10,11). ZSWIM8 is required for murine perinatal viability and for destabilization of most short-lived miRNAs, which suggests biological importance of TDMD11-13. Here, biochemical and cellular assays establish AGO binding and polyubiquitylation by the ZSWIM8-CUL3 E3 ligase as the key regulatory steps of TDMD, and thereby define a unique cullin-RING E3 ligase class. Cryogenic electron microscopy analyses show ZSWIM8 recognizing distinct AGO and RNA conformations shaped by pairing of the miRNA to the trigger. Specificity of AGO ubiquitylation is established through generalizable RNA-RNA, RNA-protein and protein-protein interactions. The substrate features recognized by the E3 ligase do not conform to a conventional degron14,15 but instead establish a two-RNA-factor authentication mechanism for specifying a protein ubiquitylation substrate.

DOI: https://doi.org/10.1038/s41586-026-10232-0
Proc Natl Acad Sci U S A. 2026 Mar 24. 123(12): e2529914123

SEL1L-HRD1 ERAD-autophagy interplay maintains mitochondrial homeostasis in brown adipocytes.

Xinxin Chen, Siwen Wang, Mauricio Torres, Sijie Hao, Shengyi Sun, Ling Qi.

  Mitochondrial integrity is central to energy homeostasis, particularly in brown adipose tissue where dynamic remodeling fuels thermogenesis. Two major proteostatic systems, the SEL1L-HRD1 endoplasmic reticulum (ER)-associated degradation (ERAD) pathway and autophagy, have been shown to intersect in vitro, but their physiological coordination in metabolically active tissues remains unclear. Here, we demonstrate that ERAD and autophagy act in synergy to safeguard mitochondrial integrity in brown adipocytes. Using various adipocyte-specific knockout (KO) mouse models and high-resolution ultrastructural 2D and 3D imaging, we show that simultaneous deletion of Sel1L and Atg7 (double KO, DKO) causes striking mitochondrial abnormalities under room temperature, absent in single KO or Sel1L-Ire1a double knockout mice. DKO adipocytes accumulate hyperfused megamitochondria extensively penetrated by ER tubules, accompanied by ER expansion, excessive ER-mitochondrial contacts, and impaired thermogenesis. These findings reveal that SEL1L-HRD1 ERAD and autophagy cooperate, rather than act redundantly, to maintain mitochondrial integrity in brown fat, uncovering a previously unrecognized mitochondrial surveillance mechanism based on ERAD-autophagy crosstalk.

Keywords:  3D FIB-SEM; ER–mitochondrial contacts; brown adipocytes; megamitochondria; thermogenesis

DOI:  https://doi.org/10.1073/pnas.2529914123
Nat Commun. 2026 03 14. pii: 2487. [Epub ahead of print]17(1):

Control of lysosome function by the GTPase-activating protein TBC1D9B and its binding partner TMEM55B.

Valentin Duhay, Miaomiao Tian, Klaudia Kosieradzka, Michael Ebner, Wen-Ting Lo, Michael Krauss, Henner-Linus Sprengel, Matthias Voss, Mara Riechmann, Jeffrey N Savas, Michael Schwake, Volker Haucke, Markus Damme.

Lysosomes are highly dynamic organelles that serve antagonistic functions as terminal catabolic stations for the degradation of macromolecules and as central metabolic decision centers for anabolic growth signaling. Lysosome dysfunction is implicated in various human diseases. The physiological roles of lysosomes are linked to the control of lysosome position and dynamics via the activity of the kinesin-activating small GTPase ARL8. How the activity of ARL8 is regulated remains poorly understood. Here, we identify the GTPase-activating Tre-2/Bub2/Cdc16 (TBC) domain protein TBC1D9B as a critical negative regulator of ARL8B function. We demonstrate that TBC1D9B is associated with the lysosomal membrane protein TMEM55B, directly binds to ARL8B-GTP, and stimulates its GTPase activity. Knockout of TBC1D9B or its binding partner TMEM55B causes lysosome dispersion, defective autophagic flux, and impairs the adaptive degradative response of cells to limiting nutrient supply. These lysosomal phenotypes of TBC1D9B loss are occluded by concomitant depletion of ARL8 in cells. Collectively, our data unravel a key role for TBC1D9B in controlling lysosome function by serving as a negative regulator of ARL8 activity.

DOI: https://doi.org/10.1038/s41467-026-70345-y
Cell. 2026 Mar 19. pii: S0092-8674(26)00105-4. [Epub ahead of print]189(6): 1768-1784.e24

Hijacking ERAD for targeted degradation of transmembrane proteins.

Haikun Song, Wei Wang, Tingfang Mei, Huiwen Zheng, Keni Ning, Xiaofan Liu, Siulam Cheung, Zhiyuan Cao, Danqi Sheng, Xiaohan Mai, Haoran Zhu, Guankai Guo, Shuaimeng Liu, Rongkai Wei, Qian Wang, Yu Cao, Yu Ding, Yiyan Fei, Rui Liu, Motoyuki Hattori, Chunquan Sheng, Boxun Lu.

  Targeted protein degradation (TPD) technologies provide huge opportunities for drug discovery, but degrading transmembrane (TM) targets remains challenging. Since TM proteins are canonically folded on the endoplasmic reticulum (ER) membrane, we hypothesized that harnessing ER-associated degradation (ERAD) may enable efficient degradation of TM proteins. Here, we established a TPD technology hijacking ERAD and named it ERAD-engaging chimeras (ERADECs), capable of degrading TM targets with high efficacy. We identified desonide as a binder of SYVN1, an ER E3 ligase mediating ERAD. We designed ERADECs targeting programmed death-ligand 1 (PD-L1) by connecting desonide to a known PD-L1 ligand and observed SYVN1- and ERAD-dependent PD-L1 degradation with high efficacy. Functionally, these ERADECs exhibited stronger tumor suppression and PD-L1-lowering effects than a clinically used PD-L1 antibody in vivo. The concept of ERADECs is also expandable to other membrane targets. Collectively, we established a platform technology hijacking ERAD to selectively degrade TM targets with remarkable efficiency.

Keywords:  E3 ligases; Hrd1; PD-L1; PROTAC; SYVN1; TPD; cancer immune; transmembrane proteins; tumor; ubiquitin

DOI:  https://doi.org/10.1016/j.cell.2026.01.018
Nat Struct Mol Biol. 2026 Mar;33(3): 394-407

Ribosome-associated quality control and related mechanisms.

Toshifumi Inada.

Ribosome-associated quality control (RQC) safeguards translation by detecting and resolving collided ribosomes and triaging their nascent chains. This Review outlines mechanisms, crosstalk and disease implications of RQC cascades and presents RQC as a 'first responder' that prevents escalation to global stress responses and provides protection against proteostasis collapse.

DOI: https://doi.org/10.1038/s41594-026-01771-1
Autophagy. 2026 Mar 18. 1-2

ATG2A connects lipid droplets and the ER to regulate lipid storage.

Helin Elhan, Justin L Korfhage, Thomas J Melia, Abdou Rachid Thiam.

  The endoplasmic reticulum (ER) must carefully regulate the levels of nonmembrane lipids such as diacylglycerol (DAG), phosphatidic acid (PA), and triacylglycerol (TAG) to maintain membrane integrity and prevent lipotoxic stress. While ATG2A is well known as a lipid transfer protein essential for autophagosome formation, its role at lipid droplet (LD) contact sites has remained unclear. In our recent work, we show that ATG2A functions beyond its typical role in autophagy as a key regulator of lipid storage, transferring DAG, TAG, and PA from the ER to LDs and recruiting the TAG synthesis enzyme DGAT2 to promote LD expansion. Without ATG2A, lipids accumulate in the ER, leading to smaller, more numerous nucleated LDs rather than proper growth. Notably, ATG2A-mediated DAG transfer recruits DGAT2 to LD surfaces, enabling local TAG synthesis that prevents nonmembrane lipid accumulation in the ER. This cooperative process reveals ATG2A's dual role in both autophagy and lipid storage, highlighting an unexpected link between autophagy machinery and lipid storage.

Keywords:  ATG2A; DGAT2; ER quality control; diacylglycerol; lipid droplets; lipid transfer

DOI:  https://doi.org/10.1080/15548627.2026.2645161
Mol Cell. 2026 Mar 19. pii: S1097-2765(26)00129-2. [Epub ahead of print]86(6): 1164-1181.e12

ZNFX1 uses two-component ubiquitin circuitry to quarantine viral RNA.

Daniel R Squair, Eilidh Rivers, Hanna Sowar, Arda Balci, Roosa Harmo, David J Wright, Gaurav Beniwal, Mathieu Soetens, Sunil Mathur, Aidan Tollervey, Nicola T Wood, Kuan-Chuan Pao, Callum Stanton, Adam J Fletcher, Satpal Virdee.

  The detection of viral RNA inside cells triggers a diverse range of antiviral responses, including global translation inhibition, interferon secretion, and RNA sequestration. Mutations in the gene zinc-finger NFX1-type containing 1 (ZNFX1) cause severe pediatric immunodeficiencies, including chronic viral infection and autoinflammation. Here, we show that ZNFX1 is an RNA helicase with cryptic and unusual bifurcating E3 ubiquitin ligase activity. Nucleotide-dependent RNA binding stimulates ZNFX1 to generate complex ubiquitin chains via a two-component ubiquitin circuit wired in parallel, with ubiquitin flux occurring via two competing paths. One route produces K63-linked polyubiquitin that drives RNA entrapment within self-propagating ZNFX1 aggregates, and the other route produces K48-linked polyubiquitin that drives ZNFX1 turnover. RNA entrapment restricts RNA virus replication and is reversible by deubiquitination. Pathogenic ZNFX1 variants are defective for viral restriction, linking RNA entrapment to antiviral immunity in vivo.

Keywords:  RNA; activity-based probes; biochemistry; ubiquitin; virology

DOI:  https://doi.org/10.1016/j.molcel.2026.02.015
EMBO J. 2026 Mar 20.

Functional rescue of a disease-linked ERAD pathway mutation via alternative splicing.

Huilun Helen Wang, Zhihong Wang, Liangguang Leo Lin, Sunil K Verma, Weronika Gniadzik, Hui Wang, Zexin Jason Li, Emily Whitestone, Lulu Jiang, Muge N Kuyumcu-Martinez, Shengyi Sun, Ling Qi.

  ER-associated degradation (ERAD) targets misfolded proteins in the endoplasmic reticulum (ER) for proteasomal degradation. Mutations in its most conserved branch involving the SEL1L-HRD1 complex cause ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI), characterized by developmental delay, microcephaly, and locomotor dysfunction. Its most severe form, ENDI with agammaglobulinemia (ENDI-A), results from a bi-allelic SEL1L-Cys141Tyr (C141Y) mutation within its fibronectin II (FNII) domain and currently lacks effective treatment. Here, we find that knock-in mouse models carrying the C141Y mutation are unexpectedly rescued via increased use of an alternative splice donor within exon 4 leading to bypass of the mutant FNII-encoding region. The resulting SEL1L variant restores ERAD activity, and rescues perinatal lethality, B cell deficiency, and neurodevelopmental defects. Leveraging this mechanism, we demonstrate that antisense oligonucleotide-mediated exon skipping in patient-derived fibroblasts generates a truncated yet functional SEL1L protein that fully restores ERAD function and ER proteostasis. These results establish RNA splicing-modulation as a viable therapeutic strategy for ERAD deficiency and broaden the clinical potential of exon-skipping therapy to diseases of protein misfolding.

Keywords:  Alternative Splicing; Anti-sense Oligonucleotide; Disease Variant; ENDI-A; SEL1L-HRD1 ERAD

DOI:  https://doi.org/10.1038/s44318-026-00757-5
EMBO J. 2026 Mar 20.

Ca²⁺ leakage is a conserved signal for non-canonical ATG8/LC3 lipidation and membrane repair.

Di Chen, Antony Fearns, Christopher J Peddie, Maximiliano G Gutierrez.

  Endomembrane damage of intracellular vesicles triggers signals that activate membrane repair in mammalian cells to restore homeostasis. However, the signals that drive diverse membrane repair recruitment at the individual organelle level are unknown. Here by recording Ca2+ leakage history with a newly developed Ca2+ probe in human macrophages, we discovered that Ca²⁺ leakage serves as a conserved signal that triggers ATG8/LC3 lipidation after different types of sterile membrane damage. The damaged compartments consisted of both single membrane and multilayered membrane structures undergoing extensive membrane remodelling. We show the complexity and acidification of these ATG8/LC3-positive compartments depends on the nature of the membrane damage trigger. Functionally, the formation of these multimembrane ATG8/LC3-positive compartments restricted membrane damage independently of canonical autophagy and the recruitment of ESCRT components CHMP2A/CHMP4B. Altogether, we show that endolysosomal Ca²⁺ leakage triggers non-canonical LC3 lipidation on damaged membranes to promote membrane repair in human macrophages.

Keywords:  Ca2+ Leakage; Lysosome Damage; Macrophages; Membrane Repair; Non‑canonical LC3 Lipidation

DOI:  https://doi.org/10.1038/s44318-026-00741-z
J Cell Sci. 2026 Mar 13. pii: jcs.264537. [Epub ahead of print]

Retrograde Golgi-to-ER transport is regulated by diacylglycerol in Saccharomyces cerevisiae.

Yujia Yang, Shuyin Yang, Shiori Ito, Hangqing Li, Takefumi Karashima, Kazuki Hanaoka, Philipp Schlarmann, Kuya Matsunaga, Qihao Jin, Kouichi Funato.

  Coat protein complex (COP) I (COPI)-mediated retrograde transport from the Golgi apparatus to the endoplasmic reticulum (ER) plays a crucial role not only in recycling mislocalized and/or misfolded proteins to the ER but also in maintaining ER and Golgi structure and function. This pathway is tightly coordinated with COPII-mediated anterograde transport to ensure cellular homeostasis. In the regulation of bidirectional vesicular trafficking, lipids act as indispensable structural components of vesicles. Among these, the cone-shaped lipid diacylglycerol (DAG) has long been known to be involved in COPI function in mammalian cells. However, whether this regulatory mechanism is conserved across species remains unknown. In this study, we identify diacylglycerol (DAG) as a key modulator of COPI-mediated retrograde transport in budding yeast, demonstrating that DAG accumulation rescues both lethality and transport defects in COPI retrieval mutants. Notably, DAG levels decrease upon inhibition of retrograde transport and increase upon its restoration. These findings suggest that DAG regulates retrograde transport in a manner that promotes COPI vesicle formation, underscoring its potential role as a lipid mediator in cellular trafficking.

Keywords:   Saccharomyces cerevisiae ; Budding yeast; COPI; Diacylglycerol; Lipid; Retrograde Golgi-to-ER transport

DOI:  https://doi.org/10.1242/jcs.264537
J Cell Biol. 2026 May 04. pii: e202506111. [Epub ahead of print]225(5):

A PTPN23-dependent ESCRT pathway is essential for constitutive secretion in mammalian cells.

Danièle Stalder, Conceição Pereira, Dick J H van den Boomen, Petia Adarska, Dilip Menon, Daniel J Fazakerley, Francesca Bottanelli, Paul J Lehner, David C Gershlick.

Secreted proteins are essential for processes like immune responses, cellular communication, and extracellular matrix remodeling. Once synthesized and processed at the Golgi, some of these proteins are packaged for delivery to the plasma membrane. While this transport and sorting rely on complex molecular machinery, the precise mechanisms remain unclear. In this study, we affinity-isolated and analyzed post-Golgi carriers by mass spectrometry. Candidate machinery was subsequently assessed in a pooled CRISPR-KO screen. This led to the identification of a rich set of new genes functionally important for Golgi-to-plasma membrane delivery including PTPN23, a component of the endosomal sorting complex required for transport (ESCRT) complex. Depletion of PTPN23, as well as the ESCRT subunits CHMP1 and VPS4, disrupts tubule fission from the trans-Golgi, impairing cargo delivery to the surface. Furthermore, the loss of PTPN23 also prevents the constitutive secretion of soluble cargoes, and of endogenous hormones and antibodies in specialized cells. We propose that PTPN23 is essential for secretion from the trans-Golgi.

DOI: https://doi.org/10.1083/jcb.202506111
Nat Commun. 2026 Mar 17.

Calcium-mediated calreticulin-IRE1α interaction drives dynamic fluctuation of IRE1α activity under chronic endoplasmic reticulum stress.

Jianwei Cao, Xudong Zhao, Yunxin Xu, Chen Yang, Yazhen Huo, Ting Li, Wenjia Gu, Lei Wang, Youjun Wang, Likun Wang.

The unfolded protein response (UPR) triggered by endoplasmic reticulum (ER) stress can be both pro-survival or pro-apoptotic, depending on the duration and intensity of the stress. ER stress under (patho)physiological conditions can last for long time, yet the dynamic regulation of the UPR under prolong ER stress is largely unknown. Here, we characterized the UPR dynamics during pharmacologically induced long-term ER stress and revealed an "up-down-up" fluctuation pattern of the IRE1α signal in various types of cells. A fluctuation of the calreticulin-IRE1α interaction intensity orchestrates dynamic regulation of IRE1α activity, which negatively correlates with the intensity of the interaction between IRE1α and BIP, a known suppressor of IRE1α. The calreticulin-IRE1α interaction is negatively affected by Ca2+ concentration, which showed "down-up-down" pattern in the ER lumen over time. Furthermore, a circadian rhythmic fluctuation of calreticulin-IRE1α interaction intensity is observed in mouse liver, accompanied by oscillation of IRE1α phosphorylation level at regular physiological conditions. Our study suggests a calcium-mediated, calreticulin-driven IRE1α activity fluctuation, representing an intermediate status that the cell adopts to cope with chronic ER stress that may exist under both pathophysiological and physiological conditions.

DOI: https://doi.org/10.1038/s41467-026-70679-7
FASEB J. 2026 Mar 31. 40(6): e71695

Disulfide Crosslinking Induces Rapid Degradation of Arc/Arg3.1 via Hsp70-Mediated Ubiquitin Ligase Pathway.

Dami So, In-Kang Song, Yeon Jung Kim, Yeonjoo Lee, Yeon Seung Park, Hee-Jung Kim, Kong-Joo Lee, Eun Joo Song.

  Activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) is an immediate-early gene (IEG) induced by stress and synaptic activity, characterized by transient expression and rapid degradation. However, the mechanisms governing its degradation remain unclear. In this study, we identify a novel degradation pathway for Arc/Arg3.1, driven by its structural features. We demonstrate that the proteasomal degradation of Arc/Arg3.1 is modulated by the Hsp70-CHIP complex, with ubiquitination being impaired in HSF1 knockout cells. The formation of a Cys34-Cys159 disulfide bond crosslinks Arc/Arg3.1 into high-molecular-weight oligomers, altering its ubiquitination pattern and degradation kinetics compared to the C159A mutant. Hydrogen-deuterium exchange mass spectrometry (HDX-MS) revealed that wild-type (WT) Arc/Arg3.1 adopts a more compact structure than the C159A mutant. Notably, the C159A mutant fails to interact with HSF1, resulting in Hsp70 induction upon heat shock. Our findings propose a feedback loop in which disulfide crosslinking of Arc/Arg3.1 induces rapid degradation through Hsp70-mediated ubiquitination, which in turn modulates the heat shock response by inhibiting HSF1 function.

Keywords:  E3 ubiquitin ligase; arc/arg3.1; disulfide formation; heat shock protein 70 (Hsp70); protein aggregation; protein degradation

DOI:  https://doi.org/10.1096/fj.202502555R
FEBS J. 2026 Mar 18.

Bip1 regulates AMPK signaling in response to endoplasmic reticulum stress.

Mengdan Zhu, Chuanhai Fu.

  The accumulation of misfolded and unfolded proteins within the endoplasmic reticulum (ER) lumen induces ER stress, which in turn triggers various consequences, such as the unfolded protein response (UPR). AMP-activated protein kinase (AMPK) is also a cellular stress sensor. However, the interplay between AMPK and ER stress remains poorly understood. In this study, we report that in the fission yeast Schizosaccharomyces pombe, the deletion of erd2, a central component for the retrieval of ER-resident proteins, leads to the accumulation of the canonical ER luminal chaperone Bip1 in the cytosol. Moreover, we demonstrate that erd2 deletion increases the levels of the AMPK upstream kinase Ssp1 in a Bip1-dependent manner, thereby promoting AMPK phosphorylation. Intriguingly, although these phenotypes are not dependent on UPR, they can also be caused by ER stress. We further identify multiple E3 ubiquitin ligases that are responsible for the regulation of Ssp1 stability, and Bip1 physically interacts with and stabilises Ssp1 by inhibiting ubiquitination of Ssp1. Additionally, we elucidate that AMPK activation, mediated by the stabilised Ssp1, is required to sustain cell viability, particularly in cells lacking Erd2. Collectively, our findings demonstrate the important role of Erd2 in the maintenance of cellular homeostasis and establish a link between ER stress and AMPK signalling.

Keywords:  AMPK; Bip1; Erd2; Schizosaccharomyces pombe; Ssp1

DOI:  https://doi.org/10.1111/febs.70496
Plant Cell Environ. 2026 Mar 17.

An RGLG E3 Ubiquitin Ligase CaSIRE1 Negatively Regulates ABA-Dependent Drought Tolerance by Destabilizing CaSAP14 in Pepper.

Hoyeol Choi, Woonhee Baek, Chae Woo Lim, Dae Sung Kim, Sung Chul Lee.

  Plants respond to drought stress primarily through the abscisic acid (ABA) signalling pathway, which is finely regulated by post-translational modifications. Among these, the ubiquitin-proteasome system plays a central role in controlling protein turnover, with E3 ligases conferring substrate specificity. Here, we identify CaSIRE1 (Capsicum annuum SAP14 Interacting RING-type E3 ligase 1), which encodes a RING-domain ligase belonging to the C3HC4 RING-type E3 ligase family, as a negative regulator of drought stress response and ABA signalling in pepper. Functional analyses revealed that silencing of CaSIRE1 in pepper enhances drought tolerance and ABA sensitivity, whereas overexpression of CaSIRE1 in Arabidopsis compromises these responses. CaSIRE1 physically interacts with CaSAP14, a stress-associated protein previously characterized as a positive regulator of drought stress response, and promotes its ubiquitination and subsequent degradation via the 26S proteasome pathway. Importantly, CaSIRE1-dependent CaSAP14 degradation is attenuated under drought conditions, resulting in increased CaSAP14 stability. Genetic analysis further demonstrated that CaSAP14/CaSIRE1 double-silenced pepper plants displayed drought-sensitive phenotypes comparable to CaSAP14-silenced plants, indicating that CaSIRE1 acts upstream of CaSAP14 in ABA signalling and drought stress response. Together, our findings uncover a CaSIRE1-CaSAP14 regulatory module that dynamically modulates protein stability to fine-tune ABA-mediated drought stress response in pepper.

Keywords:  E3 ligase; abscisic acid; drought stress; protein stability; ubiquitination

DOI:  https://doi.org/10.1111/pce.70492
Protein Sci. 2026 Apr;35(4): e70539

Small heat shock proteins HspB1 and HspB5 differentially alter the condensation and aggregation of the TDP-43 low-complexity domain.

Thomas B Walker, Joshua W Trowbridge, Shannon McMahon, Nicholas R Marzano, Lauren Rice, Justin J Yerbury, Heath Ecroyd, Luke McAlary.

  TAR DNA-binding protein 43 (TDP-43) is a nucleic acid-binding protein that regulates processes of mRNA metabolism, during which it undergoes condensation mediated by its C-terminal low-complexity domain (TDP-43LCD). TDP-43 aggregation and condensation are associated with neurodegenerative disease. However, the proteostasis mechanisms that regulate these processes remain elusive. Some evidence has shown that the molecular chaperone small heat shock protein HspB1 binds to and regulates the cytoplasmic phase separation of TDP-43, indicating that other small heat shock proteins may have similar effects. Here, we demonstrate divergent behaviors for HspB1 and its homolog HspB5 on TDP-43LCD condensation and aggregation. In addition to inhibiting TDP-43LCD aggregation, HspB1 partitions into TDP-43LCD condensates and increases the dynamic exchange of TDP-43LCD within condensates and with the surrounding solution. Phosphorylation-mimicking mutations within HspB1 enhance these effects. HspB5 inhibits TDP-43LCD aggregation more effectively than HspB1 and partitions into TDP-43LCD condensates, where it delays the pathological transition of the condensate to a gel/solid. We identify the N- and C-terminal regions of HspB1 and HspB5 to be crucial for the chaperone effects, and highlight the role of sequence diversity within these regions in defining small heat shock protein function. These findings demonstrate that HspB1 and HspB5 are regulators of TDP-43 phase separation and aggregation and may be potential therapeutic targets in mitigating toxic TDP-43 aggregation in neurodegenerative disease.

Keywords:  amyotrophic lateral sclerosis; chaperones; fibrillation; liquid–liquid phase separation; proteostasis

DOI:  https://doi.org/10.1002/pro.70539
bioRxiv. 2026 Mar 06. pii: 2026.03.04.709563. [Epub ahead of print]

PERK Deficiency Amplifies Molecular, Structural, and Network Vulnerability to Repetitive Mild Traumatic Brain Injury.

Marangelie Criado-Marrero, Sakthivel Ravi, Daylin Barroso, Tristyn N Garza, Diana M Cuestas Torres, Christian Lessard, Juan Pablo Castano, MacKenzie L Bolen, Uriel Rubinovich, Stefan Prokop, Paramita Chakrabarty, Laura P W Ranum, Marcelo Febo, Jose Francisco Abisambra.

Repetitive mild traumatic brain injury (rmTBI) produces cumulative cellular stress that can lead to progressive brain dysfunction, yet the mechanisms governing vulnerability to repeated injury remain unclear. Protein kinase RNA-like endoplasmic reticulum kinase (PERK) regulates cellular proteostasis through the unfolded protein response and is implicated in neurodegeneration and acute brain injury. Here, we directly tested the role of PERK deficiency in shaping the brain's response to rmTBI. Using a mouse model of neuronal PERK deficiency, we combined spatial proteomics and tissue analyses with resting-state functional MRI and diffusion tensor imaging to assess molecular, functional, and structural outcomes after rmTBI. PERK deficiency increased susceptibility to rmTBI-induced disruption of protein homeostasis, altered large-scale functional connectivity, and exacerbated white matter microstructural changes consistent with axonal and myelin damage. Molecular alterations were spatially aligned with imaging-defined network and white matter abnormalities. These findings identify PERK signaling as a key determinant of brain resilience to repetitive mild injury and link ER stress dysregulation to network-level dysfunction following rmTBI.

DOI: https://doi.org/10.64898/2026.03.04.709563
Nucleic Acids Res. 2026 Mar 19. pii: gkag240. [Epub ahead of print]54(6):

An RNA structural switch controlling bacterial toxin translation.

Athina Eleftheraki, Andrés Escalera-Maurer, Elsa D M Hien, Alice Virciglio, Maéva Conangle, Nicolas J Tourasse, Anaïs Le Rhun, Erik Holmqvist.

Type I toxin-antitoxin systems (T1TAs) rely on tight posttranscriptional control to prevent inadvertent toxin synthesis, yet the molecular mechanisms underlying this control are highly diverse. Here, we uncover an RNA-based mechanism that controls translation initiation in the enterobacterial timPR system. Unlike most T1TAs, which typically rely on ribonucleolytic messenger RNA (mRNA) processing to relieve ribosome binding site sequestration, the primary timP toxin mRNA is activated through a purely structural RNA switch. Using a FASTBAC-Seq loss-of-function screen with biochemical and phenotypic assays, we here identify key RNA interactions that govern this switch. Translation initiation at timP requires formation of (i) a pseudoknot in the 5' untranslated region, and (ii) a long-range interaction that destabilizes the ribosome-binding-site-sequestering stem-loop, rendering the Shine-Dalgarno sequence accessible for pre-initiation complex formation. Conversely, an alternative interaction locks the mRNA in an inactive state. Our findings reveal a structural RNA switch that controls toxin expression without the need for enzymatic processing and demonstrate an alternative mechanism for translation initiation in bacteria.

DOI: https://doi.org/10.1093/nar/gkag240
bioRxiv. 2026 Mar 02. pii: 2026.02.27.708386. [Epub ahead of print]

Hierarchical membrane-chromatin tethering buffers nuclear envelope assembly against alterations in lipid flux.

Sarah Barger, Sofia Sepùlveda, Han Yang, Marc Goudge, Shoken Lee, Neale Ridgway, Shirin Bahmanyar.

In open mitosis, a single nuclear envelope (NE) forms around segregated chromosomes despite an excess of membrane-chromatin tethers. Here, we identify a hierarchical relationship between the BAF binding membrane tethers LEM-2 and Emerin, in which LEM-2 preferentially accumulates at BAF binding sites during postmitotic NE assembly and limits Emerin accumulation in C. elegans embryos. When LEM-2 is absent, Emerin occupies these sites and compensates for LEM-2 loss; however, NE formation becomes sensitized to ER membrane abundance - excessive phospholipid production through loss of CTDNEP1/CNEP-1 causes membrane invasions in interchromosomal regions and, across multiple systems, formation of lobulated, unstable nuclei with abnormal Emerin accumulations. We find that human CTDNEP1 regulates the NE-associated enzyme CCTa; to maintain phosphatidylcholine (PC) homeostasis through preventing delayed PC breakdown. Restoring PC levels rescues Emerin assembly and nuclear morphology defects resulting from the combined loss of CTDNEP1 and LEMD2. Together, these findings link membrane-chromatin tethering to ER lipid content and reveal preferential tethering as a determinant of NE assembly fidelity, with broad relevance to disease-related nuclear defects.

DOI: https://doi.org/10.64898/2026.02.27.708386
EMBO J. 2026 Mar 20.

Targeting ubiquitin signaling vulnerabilities in KEAP1-inactivated lung cancer.

Varun Jayeshkumar Shah, Oliver Hartmann, Martin Wegner, Cristian Prieto-Garcia, Rubina Kazi, Viktoria von Heyl Zu Herrnsheim, Amin Wanli, Igor Mačinković, Bianka Bohnacker, Koraljka Husnjak, Dmitry Namgaladze, Mathias Rosenfeldt, Manuel Kaulich, Markus E Diefenbacher, Ivan Dikic.

  Lung cancer cells rely on protein homeostasis regulators, particularly the ubiquitin-proteasome system (UPS), to sustain malignancy. Genetic alterations in UPS components, such as E3 ubiquitin ligases (E3s) and deubiquitinating enzymes (DUBs), are common and create context-dependent therapeutic dependencies. To investigate how these genetic alterations drive tumor formation, we conducted CRISPR screens on metabolically stressed murine lung cancer models and identified specific cancer dependencies, including ubiquitin ligase subunit KEAP1. Although KEAP1 is frequently mutated in aggressive non-small cell lung cancers (NSCLC, ~15%), our findings reveal an unexpected proto-oncogenic role for KEAP1 in a genetically defined subset of NSCLC. Mechanistically, Keap1 deletion activated Nrf2 and upregulated Aldh3a1. This led to elevated reductive stress and suppressed tumor growth. Given the poor prognosis of KEAP1-mutated patients, combinatorial CRISPR dropout screens revealed druggable E3s and DUBs as Keap1-dependent co-vulnerabilities. Notably, depleting these co-dependencies, such as the E3 ligases Herc2, Ubr4 and Huwe1 ablated the in vivo development of Keap1-inactivated tumors. We demonstrate that targeting the UPS represents an underexplored, promising therapeutic approach for patients with KEAP1-inactivated tumors, especially under metabolic stress.

Keywords:  CRISPR/Cas9; Keap1; NSCLC; Reductive Stress; Ubiquitin-Proteasome System

DOI:  https://doi.org/10.1038/s44318-026-00737-9
J Biol Chem. 2026 Mar 17. pii: S0021-9258(26)00248-6. [Epub ahead of print] 111378

Glycolipid transfer protein modulates vesicular trafficking from the endoplasmic reticulum in HeLa cells.

Henrik Nurmi, Linda Englund, Alina Henriksson, Max Lönnfors, Peter Mattjus.

The glycolipid transfer protein (GLTP) has been proposed to function as a sensor and regulator of glycosphingolipid homeostasis in the cell, as levels of GLTP directly influence the quantities of many glycosphingolipids. Furthermore, through its interaction with the endoplasmic reticulum (ER) membrane protein VAPA (vesicle-associated membrane protein-associated protein A), GLTP may also be involved in regulating intracellular vesicular transport. Here we show that GLTP knockout leads to the sequestration of COPII coat proteins Sec23A and Sec31A at the ERES. The intracellular localization of the small GTPase Sar1A is altered in GLTP knockout cells and in cells expressing a GLTP mutant incapable of VAPA binding, indicating a correlation between the inhibition of the GLTP/VAPA interaction and the altered localization of Sar1A. We also observed alterations in the intracellular localization of the Sar1A-activating GEF Sec12 in GLTP knockout cells, implying a Sec12-activating role of the GLTP/VAPA interaction. Knockout of GLTP does not alter the amounts of other lipid transfer proteins or glucosylceramide synthase, indicating that a decrease in the levels of these proteins is not responsible for the decreased GSL levels associated with GLTP knockout. We propose a role for GLTP in modulating the COPII vesicle trafficking pathway, thereby indirectly regulating the cellular glycosphingolipid homeostasis by controlling the vesicular ceramide transport from the ER to the Golgi. Moreover, the discovery that GLTP localizes to the nucleus at the onset of the DNA-replicating S-phase of the cell cycle introduces an entirely new and unexpected dimension to GLTP's in vivo function.

DOI: https://doi.org/10.1016/j.jbc.2026.111378
Mol Cell. 2026 Mar 19. pii: S1097-2765(26)00126-7. [Epub ahead of print]86(6): 1099-1115.e10

ER-tethering directs TREX1 penetration of a BAF-dependent barrier at micronuclei.

Yanyang Chen, Roshan Xavier Norman, Eléonore Toufektchan, Xiaohan Luan, Abraham Shim, Hannah Rosenberg, Marton Tibor Kovacs, Ashley Nichols, James Hickling, Paolo Cifani, Alex Kentsis, Wen Zhou, John Maciejowski.

  Micronuclei are membrane-encapsulated nuclear aberrations that form following chromosome segregation errors. Micronuclear membrane collapse permits access of the pattern recognition receptor cGAS and its antagonist, the TREX1 exonuclease. TREX1 endoplasmic reticulum tethering is essential for invasion into ruptured micronuclei, but the mechanisms underlying this dependency are unknown. Here, we identify BAF as a key regulator of TREX1 activity at micronuclei. BAF accumulates at micronuclei following membrane collapse and augments TREX1 recruitment via interactions with LEM-domain proteins. Despite delayed entry, TREX1 exhibits enhanced micronuclear DNA degradation and independence from ER-tethering in BAF-deficient cells. Recombinant BAF inhibits TREX1-mediated DNA degradation in vitro via DNA-binding. BAF similarly outcompetes cGAS for micronuclear DNA and limits cGAS-dependent immune signaling. These findings reveal a BAF-dependent protective barrier to the diffusive entry of DNA-binding proteins into ruptured micronuclei that explains TREX1 ER-tethering requirements for suppressing innate immune responses in chromosomally unstable cells.

Keywords:  BAF; STING; TREX1; cGAS; chromosomal instability; chromothripsis; micronuclei

DOI:  https://doi.org/10.1016/j.molcel.2026.02.012
Nat Chem. 2026 Mar 19.

Degradation of G-quadruplex-binding proteins in chromatin using G4-ligand-based proteolysis-targeting chimeras.

Zixuan Wang, Xuan He, Xiaoyun Zhang, Jochen Spiegel, Sean M Flynn, Shankar Balasubramanian.

Targeted protein degradation can intervene with the function of disease-related proteins, but most current approaches rely on direct ligand engagement of a protein target, limiting their applicability to proteins that are difficult to bind selectively. Here we present a conceptually unique approach to degrade proteins associated with DNA G-quadruplex (G4) secondary structures in a chromatin context. G4s are non-canonical nucleic acid structures that form at regulatory regions of transcriptionally active genes in open chromatin, and are abundant in cancer states. Although many proteins recognize or regulate G4 structures, selectively targeting G4-binding proteins in their native chromatin environment is challenging. Our bifunctional molecules are proteolysis-targeting chimeras that bind naturally occurring G4s, recruit E3 ubiquitin ligases and degrade G4-specific transcription factors and chromatin remodellers such as FUS, SMARCA4 and ATRX. These proteins are important therapeutic targets that play crucial roles in transcription regulation and DNA repair. Our approach has the potential to be exploited in a therapeutic strategy to target diseases characterized by aberrant G4 activity, such as cancers.

DOI: https://doi.org/10.1038/s41557-026-02111-y
PLoS Pathog. 2026 Mar 17. 22(3): e1013974

The ubiquitin ligase CBL and Fas-associated factor 2 cooperate to regulate the innate immune response to M. tuberculosis.

Tina Truong, Abigail Ray, Kelsey Martin, Nicholas A Bates, Michelle Salemi, Brett S Phinney, Bennett H Penn.

As a first line of host defense, macrophages must be able to effectively sense and respond to diverse types of pathogens, and while a particular response may be beneficial in some circumstances, it can be detrimental in others. Upon infection, Mycobacterium tuberculosis (Mtb) induces proinflammatory cytokines and activates antibacterial responses. Surprisingly, Mtb also triggers antiviral responses that actually hinder the ability of macrophages to restrict Mtb growth. In Mtb-infected macrophages, the ubiquitin ligase CBL suppresses antiviral responses and preserves the antibacterial capacity of the macrophage. However, the mechanisms by which CBL regulates immune signaling are unknown. We found that CBL controls responses to multiple immune stimuli and broadly suppresses the expression of antiviral response genes. We used mass spectrometry to identify potential CBL substrates, and found, in total, over 46,000 ubiquitylated peptides in Mtb-infected macrophages, including roughly 400 peptides with CBL-dependent ubiquitylation. We then performed genetic interaction analysis of CBL and its putative substrates, and identified the Fas-associated factor 2 (FAF2) adapter protein as a key signaling molecule downstream of CBL. Together, these analyses reveal thousands of new ubiquitin-mediated signaling events and identify an important new regulator of immune signaling.

DOI: https://doi.org/10.1371/journal.ppat.1013974
Cell Rep. 2026 Mar 17. pii: S2211-1247(26)00170-1. [Epub ahead of print]45(4): 117092

Calmodulin-like protein condensates decode PAMP-induced nuclear calcium to activate plant immunity.

Weiping Mo, Zhuo Liu, Xiaoyang Zhang, Shulei Li, Anguo Huo, Yiwen Gao, Qiujiao Yang, Zhuangzhi Zhou, Liping Yu, Lei Li.

  Calcium signatures are key responses to diverse environmental stresses, yet how distinct calcium signals within confined subcellular compartments are decoded remains poorly understood. Calmodulin proteins, serving as canonical calcium sensors, play a vital role in downstream signaling. Notably, plants uniquely possess calmodulin-like (CML) proteins that contain EF-hand motifs and may function as specialized calcium sensors. Here, we find that CML49 and CML50, both of which contain EF-hands and intrinsically disordered regions (IDRs), contribute to pathogen resistance by forming molecular condensates. Pathogen-associated molecular pattern (PAMP) perception induces nuclear calcium signals that promote CML49 and CML50 condensate formation in an EF-hand- and IDR-dependent manner. These condensates sequester the WRKY11/17 transcription factors, thereby suppressing their immune-inhibitory activity. Our findings indicate that CML49/50-mediated condensate assembly spatially silences negative regulators and provides a mechanism for decoding nuclear calcium dynamics to activate plant immune responses.

Keywords:  CP: molecular biology; CP: plants; WRKY; calcium signal; calmodulin; molecular condensate; plant immunity; transcriptional reprogramming

DOI:  https://doi.org/10.1016/j.celrep.2026.117092
Open Biol. 2026 Mar 18. pii: 250220. [Epub ahead of print]16(3):

STIM1 and endoplasmic reticulum-plasma membrane contact sites oscillate independently of calcium-induced calcium release.

Ding Xiong, Cheesan Tong, Suet Yin Sarah Fung, Samantha McClellan, Yang Yang, Jeffery Yong, Min Wu.

  Calcium (Ca²+) release from intracellular stores, Ca²+ entry across the plasma membrane and their coordination via store-operated Ca²+ entry (SOCE) are critical for receptor-activated Ca²+ oscillations. However, the precise mechanism of Ca²+ oscillations and whether their control loop resides at the plasma membrane or intracellularly remains unresolved. By examining the dynamics of stromal interaction molecule 1 (STIM1), an endoplasmic reticulum (ER)-localized Ca²+ sensor that activates the Orai1 channel on the plasma membrane for SOCE, in mast cells, we found that a significant proportion of cells exhibited STIM1 oscillations with the same periodicity as Ca²+ oscillations. These cortical oscillations, shared with ER-plasma membrane (ER-PM) contact site proteins, were only detectable using total internal reflection fluorescence microscopy. Notably, STIM1 oscillations could occur independently of Ca²+ oscillations. Simultaneous imaging of cytoplasmic Ca²+ and ER Ca²+ with CEPIA1er revealed that receptor activation does not deplete ER Ca²+, whereas receptor activation without extracellular Ca²+ influx induces cyclic ER Ca²+ depletion. However, under such non-physiological conditions, cyclic ER Ca²+ oscillations lead to sustained STIM1 recruitment, indicating that oscillatory Ca²+ release is neither necessary nor sufficient for STIM1 oscillations. Using optogenetic tools to manipulate ER-PM contact site dynamics, we found that persistent ER-PM contact sites reduced the amplitude of Ca²+ oscillations without alteration of oscillation frequency. Together, these findings suggest an active cortical mechanism governs the rapid dissociation of ER-PM contact sites, thereby controlling amplitude of oscillatory Ca²+ dynamics during receptor-induced Ca²+ oscillations.

Keywords:  calcium oscillations; dynamical systems; endoplasmic reticulum calcium imaging; optogenetics

DOI:  https://doi.org/10.1098/rsob.250220
Science. 2026 Mar 19. eadw0288

Human DHX29 detects nonoptimal codon usage to regulate mRNA stability.

Fabian Hia, Yitong Wu, Masanori Yoshinaga, Sakurako Goto-Ito, Wakana Iwasaki, Koshi Imami, Hirotaka Toh, Peixun Han, Ting Cai, Takayuki Ohira, Akira Fukao, Daron M Standley, Yuichi Shichino, Masaki Takegawa, Toshinobu Fujiwara, Tsutomu Suzuki, Shintaro Iwasaki, Michael C Bassik, Takuhiro Ito, Osamu Takeuchi.

Synonymous codon usage controls global gene expression in both prokaryotic and eukaryotic species. Nonoptimal codons are known to induce mRNA decay; however, the underlying molecular mechanism remains poorly understood in human cells. Through genome-wide CRISPR screening, we identified the RNA-binding protein DHX29 as a critical regulator of codon-dependent gene expression. Cryogenic electron microscopy and selective ribosome profiling demonstrated that DHX29 directly interacts with the A-site entrance of the translating 80S ribosome, the binding site for the eEF1A•GTP•aminoacyl-tRNA ternary complex, suggesting a role in monitoring aminoacyl-tRNA sampling. Proteomic analysis further revealed that DHX29 recruits the GIGYF2•4EHP complex to mediate global suppression of nonoptimal mRNAs. These findings establish a mechanistic link between synonymous codon usage and the regulation of gene expression.

DOI: https://doi.org/10.1126/science.adw0288
Commun Biol. 2026 Mar 21.

β-arrestin1 orchestrates endosomal signaling to regulate translational control of circadian light entrainment.

Brittany Mascarenhas, Shavanie Seecharran, Nicholas A Boehler, Muhammad Wahid, Hai-Ying Mary Cheng.

In mammals, circadian entrainment relies on signaling pathways that translate light input into molecular changes within the central pacemaker, the suprachiasmatic nucleus (SCN). Here, using β‑arrestin1 (ARRB1)-deficient mice, we identify a critical role for β‑arrestin1 in this process, showing that endosomal signaling underlies key steps in clock resetting. We demonstrate that ARRB1 is required for PAC1 receptor internalization and for the activation of endosomal signaling in response to light or PACAP. ARRB1‑dependent PAC1 endosomal signaling activates an ERK1/2-RSK1-S6 cascade that enhances protein translation and contributes to the induction of PER proteins. Transcriptional responses remain intact, underscoring the spatial specificity of ARRB1 function. Our findings position endosomes as critical subcellular hubs for circadian signal transduction and reveal a non-canonical, β-arrestin1-dependent entrainment mechanism that operates through translational control. Together, these results challenge traditional GPCR signaling paradigms and establish endosome-based signaling as a key regulator of circadian timekeeping.

DOI: https://doi.org/10.1038/s42003-026-09905-3
Curr Opin Struct Biol. 2026 Mar 17. pii: S0959-440X(26)00028-X. [Epub ahead of print]98 103246

Toward a unifying mechanistic model of eukaryotic translation initiation through integrative single-molecule, structural, and computational insights.

Brennan Ashwood, Victoria Stalls, Ruben L Gonzalez.

During eukaryotic translation initiation, initiation factor proteins and the ribosomal small subunit undergo binding and dissociation reactions and conformational rearrangements that properly assemble a ribosome at the start codon of a messenger RNA. Building on extensive genetic and biochemical studies, single-molecule fluorescence experiments are revealing the time-dependent pathways of factor binding to, and dissociation from, the ribosomal small subunit and messenger RNA during initiation. Nonetheless, essential binding and/or dissociation events, conformational rearrangements, and the coupling between binding and conformational changes remain kinetically uncharacterized. Here, we summarize the status of single-molecule investigations of initiation and advocate for integrating single-molecule microscopy, structural biology, and molecular simulations to enable a time-dependent, molecular description of this fundamental step in gene expression.

DOI: https://doi.org/10.1016/j.sbi.2026.103246
Nat Commun. 2026 Mar 15.

INSIG1/2 succination mediated by the moonlighting function of ADSL promotes lipogenesis and liver tumorigenesis.

Yuran Duan, Shuo Wang, Jianyu Liu, Wenxing Qin, Yuli Shen, Yueru Hou, Xue Sun, Yanni Lin, Zhiqiang Hu, Bofei Dong, Yanli Bi, Huang Yang, Min Li, Liwei Xiao, Qingang Wu, Xueli Bai, Yuhao Wang, Gaopeng Li, Yuan Ding, Zhengwei Mao, Yang Luo, Zhimin Lu, Tong Liu, Daqian Xu, Shijian Liu, Peng Zhan, Zheng Wang.

Aerobic glycolysis supports tumor growth, but how tumor cells sense glucose to coordinate biosynthesis remains largely unclear. Here we show that in hepatocellular carcinoma cells, glucose-activated PKCε phosphorylates the purine synthesis enzyme ADSL, triggering its translocation to the endoplasmic reticulum. ADSL then promotes succination of INSIG1/2, which disrupts the interaction between INSIG proteins and SCAP, leading to the translocation of the SCAP-SREBP complex to the Golgi, the activation of SREBP-1 and the transcription of downstream lipogenesis-related genes, proliferation of tumor cells, and tumorigenesis in mice. Through virtual screening, we identify Elsulfavirine, an approved HIV drug, which blocks ADSL-INSIG interaction and suppresses SREBP-1 activation induced by glucose. Combining Elsulfavirine with Lenvatinib synergistically inhibits tumor growth. Clinically, ADSL phosphorylation and INSIG succination correlate with SREBP-1 activation and poor prognosis in human HCC. In summary, these findings reveal a repurposing mechanism by which tumor cells coordinate glucose metabolism and lipogenesis via a moonlighting function of ADSL and underscore a repurposing strategy for liver cancer therapy.

DOI: https://doi.org/10.1038/s41467-026-70583-0
bioRxiv. 2026 Mar 05. pii: 2026.03.03.709370. [Epub ahead of print]

Intrinsically disordered SERBP1 regulates translation through topology-driven G-quadruplex recognition.

Antoine Baudin, Hoang H Dinh, Kira Breunig, Xuifen Lei, Xiaoping Xu, Luiz O Penalva, David S Libich.

Serpine mRNA-binding protein 1 (SERBP1) is an intrinsically disordered RNA-binding protein that regulates translation and ribosome biogenesis through interactions with ribosomes and other molecular complexes. Despite its regulatory importance and implication in cancer development, the molecular basis of SERBP1 RNA recognition remains poorly understood. Here, we characterize the G-quadruplex (G4)-binding properties of SERBP1. Using NMR spectroscopy and biophysical assays, we show that SERBP1 binds parallel G4s, both RNA and DNA, with low micromolar affinity through a conserved mechanism. Molecular dynamics and docking simulations reveal an encircling mechanism in which the RGG box wraps around the G4 while downstream C-terminal serine residues stabilize the complex through hydrogen bonding. Phosphomimetic mutations of key serines disrupt this stabilization and reduce binding affinity, identifying phosphorylation as a regulatory switch for SERBP1 activity. Recognition is driven by G4 topology rather than nucleotide sequence, establishing SERBP1 as a broad-specificity G4-binding protein. We further demonstrate that SERBP1 regulates mTOR expression in glioblastoma cell lines through G4 elements in the mTOR 5' UTR, and that SERBP1 depletion synergizes with mTOR inhibition to reduce cell growth. These results establish SERBP1 as a G4 adaptor protein and represent, to our knowledge, the first detailed characterization of G4 recognition by a fully disordered domain, providing a molecular framework for targeting SERBP1-G4 interactions in cancer.
Significance Statement: SERBP1 is overexpressed in multiple cancers and regulates key cellular processes, yet how it recognizes its RNA targets has remained unclear. We show that SERBP1 binds G-quadruplex structures through an encircling mechanism in which its RGG box and adjacent C-terminal serine residues lock around the G4 topology, and that phosphorylation of these serines acts as a switch to modulate binding. Recognition is driven by G4 topology rather than nucleotide sequence, positioning SERBP1 as a general G4 adaptor that recruits helicases to resolve these structures and license translation. We demonstrate this principle in glioblastoma, where SERBP1 regulates mTOR expression through direct recognition of G4 elements in the mTOR 5' UTR, and its depletion synergizes with mTOR inhibition. These findings provide the first molecular characterization of G4 recognition by a fully disordered domain and establish a direct link between SERBP1-G4 interactions and cancer-relevant translational regulation.

DOI: https://doi.org/10.64898/2026.03.03.709370
Commun Biol. 2026 Mar 18.

Degron models: a toolbox for rapid in vivo depletion of essential proteins regulating mRNA metabolism.

Wiktor Antczak, Marcin Szpila, Katarzyna Sałas, Patrycja Daszczuk, Vanessa Linke, Marta Miączyńska, Andrzej Dziembowski, Olga Gewartowska.

Due to their essentiality, studying proteins involved in fundamental processes in vivo is challenging. PROTAC-based systems offer time-controlled protein depletion, but their characterization in vivo remains limited. Here, with an efficient direct zygote editing protocol, we generate degron-tag models (dTAG/FKBP or BromoTag) for seven genes involved in therapeutic and endogenous mRNA metabolism (Cnot1, Pan2, Tent5a, Tent4b, Dcp2, Rnasel, Tsg101). Degron tags occasionally cause phenotypes that can be mitigated by tag position or tagging system change. In cells, both approaches yield rapid and sustained degradation. In mice, dTAG depletion is effective but varies by protein and administration route, whereas BromoTag shows no in vivo activity. We showcase the utility of these models through an analysis of CNOT1's roles in cell division, immunity, and poly(A) tail maintenance. We present a valuable toolbox for studying mRNA metabolism in mammalian models, while providing a benchmark for applying degron-tag models to study other biological processes.

DOI: https://doi.org/10.1038/s42003-026-09828-z
FEBS Lett. 2026 Mar 16.

Valosin-containing protein counteracts ATP-driven dissolution of FUS condensates through its ATPase activity in vitro.

Hitomi Kimura, Shin-Ichi Tate, Kyota Yasuda.

  Fused in sarcoma (FUS) forms phase-separated condensates implicated in amyotrophic lateral sclerosis (ALS). Although millimolar ATP concentrations paradoxically dissolve FUS condensates through hydrotropic activity, condensates nevertheless persist in cells, suggesting active regulatory mechanisms. Here, using a reconstituted system, we show that the AAA+ATPase valosin-containing protein (VCP) counteracts ATP-driven dissolution of FUS condensates. VCP preserved both wild-type and ALS-linked P525L condensates under high ATP conditions, and this protection required catalytic ATPase activity rather than stable partitioning into condensates. The effect was abolished by the D2-specific inhibitor ML240. Our findings establish direct biochemical evidence that VCP ATPase activity maintains FUS condensates under high ATP conditions, highlighting ATPase-driven enzymatic control of liquid-liquid phase separation as a potential general principle with implications for neurodegeneration.

Keywords:  adenosine triphosphate; amyotrophic lateral sclerosis; fused in sarcoma; liquid–liquid phase separation; valosin‐containing protein

DOI:  https://doi.org/10.1002/1873-3468.70328
Nat Commun. 2026 Mar 19.

FGF1 orchestrates circadian hepatic triglyceride secretion.

Benan Pelin Sermikli, Sihao Liu, Kyeongkyu Kim, Linnea Hases, Tim van Zutphen, Ashley Untereiner, Jocelyn Torres, Mingxiao He, Lillian Crossley, Yang Dai, Jonathan Zhu, Chandra Lekha Koopari, Weiwei Fan, Morgan L Truitt, Johan W Jonker, Annette R Atkins, Michael Downes, Ronald M Evans.

Metabolic dysfunction-Associated Steatotic Liver Disease (MASLD) represents a global health crisis associated with dysregulated hepatic triglyceride (TG) synthesis, oxidation and secretion. Despite progress in targeting hepatic lipid synthesis/oxidation for MASLD treatment and a well-documented relationship between circadian rhythms and lipid metabolism, the adaptive mechanisms coordinating TG secretion with circadian timing remain incompletely understood. Here we identify an autocrine regulatory pathway where circadian hepatic Fibroblast Growth Factor 1 (Fgf1) expression synchronizes diurnal TG secretion with the active phase. FGF1 activation of FGFR4 induces an mTORC1-IRE1-XBP1 signaling cascade involving atypical IRE1 activation that promotes TG secretion. Consistently, dietary-driven MASLD is exacerbated in liver-specific FGF1 knockout mice, while exogenous FGF1 halts disease progression in a Metabolic dysfunction-Associated Steatohepatitis (MASH) mouse model. This study causally associates FGF1 circadian rhythmicity with TG secretion to establish FGF1 as a crucial pacemaker in hepatic lipid homeostasis.

DOI: https://doi.org/10.1038/s41467-026-70849-7
Gastroenterology. 2026 Mar 16. pii: S0016-5085(26)00233-7. [Epub ahead of print]

Identification of a druggable target that predicts postoperative Crohn's disease recurrence.

Sare Verstockt, Julian Schwärzler, Peter Willeit, Gabriele Bislenghi, Moritz Meyer, Lisa Mayr, Kathleen Machiels, Gert De Hertogh, Matthias Lenfant, Laura Scheffauer, Felix Grabherr, Deborah Sarah Jans, Saeed Abdurahiman, Isabelle Cleynen, Almina Jukic, Luis Zundel, Patrizia Moser, Lukas Forer, Martina Witsch-Baumgartner, Marc Ferrante, João Sabino, André D'Hoore, Michael Hess, Arthur Kaser, Richard S Blumberg, Robert Koch, Lionel Le Bourhis, Nassim Hammoudi, Dominique Cazals-Hatem, Séverine Vermeire, Herbert Tilg, Matthieu Allez, Bram Verstockt, Timon E Adolph.

   BACKGROUND & AIMS: Molecular phenotyping of Crohn's disease (CD) trajectories after ileocolonic resection (ICR) enables the identification of evolving disease mechanisms and related biomarker discovery. Here, we aimed at identifying a pathogenic node with predictive value for endoscopic disease recurrence after ICR in CD.
METHODS: We performed unbiased transcriptomics of the postoperative ileum, comparing patients with an endoscopic Rutgeerts score i0 to those with ≥i2b (n=36). A potential biomarker from this analysis, was then validated at the protein level by quantitative confocal microscopy on tissue slides, and its value for predicting endoscopic recurrence at resection was assessed in three independent ICR cohorts (total n=241). Functional implications and therapeutic potential were investigated in mouse enteritis models.
RESULTS: Patients with endoscopic CD recurrence exhibited a transcriptional node characterized by reduced Glutathione peroxidase 4 (GPX4) expression, which confined to the intestinal epithelium. Reduced intestinal epithelial GPX4 expression was already observed at the time of ICR and predicted endoscopic recurrence in addition to established clinical risk factors in a patient-level meta-analysis. Intestinal epithelial GPX4 expression was a surrogate of its enzymatic activity, inversely correlated with a mucosal endoplasmic reticulum (ER) stress signature, but was unrelated to a GPX4 genetic variant associated with CD susceptibility, histologic severity of inflammation or clinical risk factors for recurrence. In mice, reduced intestinal epithelial Gpx4 expression fueled ER stress and enabled severe enteritis, which was ameliorated by restoration of epithelial GPX4 expression with selenium supplementation.
CONCLUSIONS: Collectively, our study identifies a druggable biomarker that improves the prediction of endoscopic CD recurrence, potentially guiding patient management and therapy in the future.

Keywords:  Crohn’s disease; Glutathione peroxidase 4; biomarker; therapeutic target

DOI:  https://doi.org/10.1053/j.gastro.2026.02.035
NAR Cancer. 2026 Mar;8(1): zcag008

Human DEAH-box helicase 8 regulates HSF1-mediated stress response and cancer-associated pre-mRNA splicing in tumour cells.

Jennifer R Tall, Robert Te Poele, Alexandra Vasile, Pradeep Ramagiri, James Campbell, Caitlin R Davies, Marissa V Powers, Toby Roe, Deivendran Sankaran, Hannah Wang, Konstantinos Mitsopoulos, Bissan Al-Lazikani, Rob L M van Montfort, Emmanuel de Billy, Paul Workman, Paul A Clarke.

Transcription factor heat shock factor 1 (HSF1) orchestrates the cellular stress response, promoting malignant transformation, unchecked proliferation, and stress-resilient survival of tumour cells. We set out to discover potentially druggable regulators of HSF1 activation and identified DEAH-box RNA helicase 8 (DHX8). We investigated the role of DHX8 in regulating HSF1 within the broader context of DHX8 function in cancer cells. DHX8 silencing induces intron retention in HSF1 transcripts, reducing HSF1 protein. Importantly, DHX8 loss significantly alters RNA processing of an HSF1-regulated cancer-associated gene signature linked to poor clinical outcomes, as well as additional oncogenic and stress-response pathways. DHX8 binds between the pre-messenger RNA (mRNA) lariat branch point and the 3' splice site, consistent with the predominance of intron-retained transcripts following DHX8 loss. We show that both the ATPase and RNA-binding activities of DHX8 are essential for its role in splicing, including processing of HSF1 mRNA. We also find that DHX8 silencing triggers apoptosis more effectively in human cancer cells than in non-tumorigenic cells. Our findings identify DHX8 as a critical regulator of stress-adaptive gene expression, highlighting its promise as a therapeutic target not only to disrupt HSF1-dependent transcriptional programs but also having broader effects in cancer cells under oncogenic stress.

DOI: https://doi.org/10.1093/narcan/zcag008
Nat Metab. 2026 Mar 18.

Lysosomal phosphoinositide turnover acts upstream of RagGTPase-mTORC1 and controls muscle growth.

Melanie Picot, Nesrine Hifdi, Mathilde Vaucourt, Melanie Mansat, Peng Li, Isabel Singer, Gaëtan Chicanne, Alexandre Stella, Shen Kuang, Caterina Miceli, Nathaniel F Henneman, Bernard Payrastre, Marie Vandromme, Odile Schiltz, Ivan Nemazanyy, Mariana E G de Araujo, Ganna Panasyuk, Julien Viaud, Michael Lämmerhofer, Karim Hnia.

Lysosomes act as metabolic signalling hubs that integrate nutrient availability to coordinate anabolic and catabolic programmes. Mechanistic target of rapamycin complex 1 (mTORC1) is activated at the lysosomal surface by amino acids through RagGTPases recruited by the lysosomal adaptor and MAPK and mTOR activator complex, yet the contribution of lysosomal lipid composition to this pathway remains unclear. Here we identify lysosomal phosphoinositides, PI3P and PI(3,5)P2, as key regulators of lysosomal adaptor and MAPK and mTOR activator complex stability and dynamics at the lysosome. These lipid pools are controlled by the phosphoinositide 3-phosphatase MTM1, mutated in myotubular myopathy, via endoplasmic reticulum-lysosome membrane contact sites. Under endoplasmic reticulum stress, MTM1-dependent phosphoinositide remodelling suppresses RagGTPase-mTORC1 signalling, thereby regulating anabolic-catabolic balance during myogenic differentiation. Restoring mTORC1 activity or lysosomal phosphoinositide homeostasis rescues Rag-dependent signalling and muscle growth in cellular and mouse models of myopathy, uncovering a lysosome-centred metabolic checkpoint with direct disease relevance.

DOI: https://doi.org/10.1038/s42255-026-01484-1