bims-mecosi 2026-03-08 papers

bims-mecosi

Biomed News

on Membrane contact sites

Issue of 2026–03–08
nine papers selected by
Verena Kohler, Umeå University

Imaging interorganelle membrane contact sites using dimerization-dependent fluorescent proteins.
Purification of the lipid transfer protein tricalbin 3 in a native environment by using an amphiphilic copolymer.
Imaging and quantifying organelle contact sites using a reversible splitFAST complementation system.
Neighbors who talk: Mitochondria-lysosome crosstalk in homeostasis.
Enhancement of Mitochondria-Associated Membranes via GSK3β Activation: A Key Contributor to Trichloroethylene-Induced Renal Damage.
STIM1-Mitofusin2 interactions tether mitochondria and melanosome contacts that promote melanosome maturation.
Mechanisms and Therapeutic Strategies of Bip-HSPA9 Axis-Mediated Endoplasmic Reticulum-Mitochondria Crosstalk Driven by Bile Acids in Gastric Intestinal Metaplasia.
USP30 alleviates intestinal ischemia-reperfusion injury by deubiquitinating MFN2 mediating the mitochondrial endoplasmic reticulum pathway.
Unconventional model organisms bend our view on mitochondrial cristae.

Methods Enzymol. 2026 ;pii: S0076-6879(26)00032-7. [Epub ahead of print]727 321-354

Imaging interorganelle membrane contact sites using dimerization-dependent fluorescent proteins.

Victoria H Williams, Chih-Hsuan Hsu, Gregory E Miner, Sarah Cohen.

  Membrane contact sites (MCSs), sites of close apposition between membrane-bound organelles, mediate key intracellular processes to coordinate organelle function and are implicated in a wide range of human diseases. Because MCSs can span as little as 10 nm of distance, the limited resolution of light microscopy can hamper the ability to study these structures in live cells. Dimerization-dependent fluorescent proteins consist of a weakly fluorescent and non-fluorescent monomer that produce greater signal when the two monomers interact, thereby allowing the user to identify sites of proximity through protein-protein interaction. Here, we describe a protocol using Contact-FP - our suite of organelle-targeted dimerization-dependent fluorescent proteins - to study MCSs using confocal or Airyscan microscopy in live cells. The protocol includes guidance for transfection, imaging, and analysis of Contact-FP biosensors. It includes instructions on how to leverage this tool to study a single MCS type, identify two MCSs involving the same organelle, or induce MCSs using high levels of transfection of Contact-FP probes. We also suggest troubleshooting steps for transfection, imaging, and analysis. This protocol provides a specific example for using this tool in U-2 OS osteosarcoma cells but is amenable to adjustment for other cell types.

Keywords:  Biosensors; Endoplasmic reticulum; Fluorescent proteins; Lipid droplets; Lysosomes; Membrane contact sites; Mitochondria; Organelles; Peroxisomes; Plasma membrane

DOI:  https://doi.org/10.1016/bs.mie.2026.01.024
Methods Enzymol. 2026 ;pii: S0076-6879(25)00524-5. [Epub ahead of print]727 417-427

Purification of the lipid transfer protein tricalbin 3 in a native environment by using an amphiphilic copolymer.

Bingke Yang, Xin Bian.

  Membrane contact sites play crucial roles in regulating cellular membrane homeostasis and ion homeostasis. However, due to limitations in technical methods, it has been challenging to effectively identify the lipid components enriched around specific membrane proteins. Therefore, it remains difficult to clarify which lipid molecules serve as substrates for lipid transfer proteins and scramblases functioning at membrane contact sites and which lipids regulate their activities. Here, we describe a system using the amphipathic polymer poly(acrylic acid-co-styrene) to purify lipid transfer protein tricalbin 3 (Tcb3), which is anchored to the endoplasmic reticulum and mediates contacts with the plasma membrane. Through this process, Tcb3 can be solubilized in aqueous solution without the need for detergent treatment, which removes the lipid molecules surrounding the proteins. This process enables purification of the lipid molecules in the native membrane environment along with Tcb3.

Keywords:  AASTY; Lipid molecules; Membrane contact sites

DOI:  https://doi.org/10.1016/bs.mie.2025.11.020
Methods Enzymol. 2026 ;pii: S0076-6879(25)00527-0. [Epub ahead of print]727 75-91

Imaging and quantifying organelle contact sites using a reversible splitFAST complementation system.

Jason A Weesner, Chi-Lun Chang.

  Organelle contact sites are crucial hubs for inter-organelle logistics; yet, visualizing these dynamic foci of sub-micro scale in living cells is challenging. In this chapter, we describe how to use the FABCON (Fluorogen-Activated Bimolecular complementation at CONtact sites) toolkit to detect and quantify contact sites. FABCON labels contact sites via a reversible, fluorogen-dependent complementation of the splitFAST system. This protocol first describes the engineering principle of FABCON, allowing customization to model systems of interest. Next, we provide detailed instructions for using FABCON to monitor mitochondria-lipid droplet interactions in mammalian cells and how to quantify levels of contact sites via intensity-based measurement and line scanning. FABCON can be broadly applied to visualize and quantify other contact sites. With proper validation and optimization, FABCON provides a robust platform to study the dynamic regulation of organelle contact sites.

Keywords:  Bimolecular fluorescence complementation; Lipid droplets; Mitochondria; Organelle contact sites; SplitFAST

DOI:  https://doi.org/10.1016/bs.mie.2025.11.023
Curr Opin Cell Biol. 2026 Mar 05. pii: S0955-0674(26)00015-3. [Epub ahead of print]100 102627

Neighbors who talk: Mitochondria-lysosome crosstalk in homeostasis.

Akriti Prashar, Rosa Puertollano.

Mitochondria are highly dynamic and multifaceted organelles that perform essential cellular functions such as producing energy, regulating metabolism, and orchestrating immune responses. Lysosomes are crucial signaling hubs that are important for nutrient sensing, signal transduction, and regulation of cellular degradation and recycling processes including the removal of damaged mitochondrial components or entire mitochondria. Together, these two organelles perform critical cellular functions. Emerging evidence links defects in both organelles to multiple diseases, underscoring how their functions are intricately linked. To coordinate their activities, mitochondria and lysosomes engage in bidirectional crosstalk, enabling reciprocal regulation of their respective functions. These 'organelle conversations' can occur through direct interactions at membrane contact sites where both organelles physically interact via stabilization by molecular tethers, or at a distance through signaling pathways. Here we discuss recent progress in our understanding of the mechanisms underlying mitochondria-lysosome crosstalk and how this communication is altered in pathological conditions.

DOI: https://doi.org/10.1016/j.ceb.2026.102627
J Biochem Mol Toxicol. 2026 Mar;40(3): e70754

Enhancement of Mitochondria-Associated Membranes via GSK3β Activation: A Key Contributor to Trichloroethylene-Induced Renal Damage.

Yu Li, Lifu Zhu, Qirui Bai, Chenghuan Wan, Chen You, Jingyi Zhao, Haibo Xie, Changhao Wu, Qixing Zhu, Jiaxiang Zhang.

  Occupational medicament-like dermatitis induced by trichloroethylene (TCE) is often linked to considerable renal impairment. However, the mechanisms underlying the renal damage remain poorly understood. The present study sought to elucidate the role of GSK3β in enhancing mitochondrial endoplasmic reticulum (ER) membrane tethering and calcium (Ca²⁺) exchange in the context of TCE sensitization-induced renal injury. Our results showed that GSK3β was localized within renal tubular epithelial cells and interacted with the IP3R1 calcium (Ca2+) channel complex at mitochondria-associated membranes (MAMs). TCE sensitization upregulated GSK3β activity and the expression of IP3R1 Ca2+ channel complex and its interactions, increased Ca²⁺ transfer from ER to mitochondria, Ca²⁺ overload, and apoptosis. The pharmacological inhibition of GSK3β disrupted the protein interaction between IP3R and the Ca²⁺ channel complex, leading to a decrease in Ca²⁺ exchange between the ER and mitochondria. This reduction resulted in a decrease in the mitochondrial Ca²⁺ concentration and an increase in the antiapoptotic ability of the cell. Coherent changes to renal function variables were also observed, demonstrating the functional relevance of the GSK3β pathway. Our results suggest that TCE sensitization damages renal tubular epithelial cells by promoting GSK3β-mediated crosstalk between the ER and mitochondria, identifying a key mechanism for TCE-induced renal injury. The findings from this study offer novel insights into the mechanisms of renal damage associated with TCE sensitization and lay down a foundation for the development of targeted preventive and therapeutic interventions.

Keywords:  GSK3β; MAMs; OMDT; mitochondrial Ca²⁺; trichloroethylene

DOI:  https://doi.org/10.1002/jbt.70754
Nat Commun. 2026 Mar 06.

STIM1-Mitofusin2 interactions tether mitochondria and melanosome contacts that promote melanosome maturation.

Isshin Shiiba, Yuto Ishikawa, Hijiri Oshio, Naoki Ito, Fuya Yamaguchi, Shun Nagashima, Hideya Ando, Keitaro Umezawa, Yuri Miura, Yuhei Araiso, Koki Nakamura, Yusuke Hirabayashi, Ryoko Inatome, Shigeru Yanagi.

Mitochondria form contact sites with multiple organelles to coordinate diverse cellular processes. Melanosomes, lysosome-related organelles, undergo stepwise maturation to synthesize and store melanin, but how they interact with mitochondria remains unclear. Here we show that mitochondria-melanosome contacts dynamically increase during melanosome maturation and are mediated by STIM1-MFN2 interactions. Using a NanoBiT-based reporter system, MiMSBiT (Mitochondria-Melanosome contact reporter applying NanoBiT), to monitor reversible mitochondria-melanosome contacts in living cells, we demonstrate that STIM1 localizes to melanosomes and promotes their contact with mitochondrial MFN2. A transient decrease in melanosomal lumen calcium induces STIM1 clustering and enhances its association with MFN2. These contacts locally increase mitochondrial ATP availability, leading to melanosome lumen acidification via proton channel activation. This acidification facilitates PMEL fibrillation, a key step in melanosome maturation. Together, our findings reveal a mechanism by which mitochondria-melanosome contacts regulate melanosome maturation.

DOI: https://doi.org/10.1038/s41467-026-70282-w
Free Radic Biol Med. 2026 Mar 04. pii: S0891-5849(26)00187-5. [Epub ahead of print]

Mechanisms and Therapeutic Strategies of Bip-HSPA9 Axis-Mediated Endoplasmic Reticulum-Mitochondria Crosstalk Driven by Bile Acids in Gastric Intestinal Metaplasia.

Qijin He, Na Chen, Shujun Gong, Shuyang Xu, Yan Song, Ping Li, Huiling Yu, Yanxi Liu, Kui Jiang, Jingwen Zhao.

  Gastric intestinal metaplasia (IM) is a critical precancerous lesion for gastric cancer (GC), strongly associated with bile reflux. While bile acids (BAs) are known drivers of IM, the underlying molecular mechanisms remain elusive. Here, we integrated multi-omics analysis, clinical validation, and preclinical models to elucidate the role of endoplasmic reticulum (ER)-mitochondria crosstalk in IM pathogenesis. We identified that the ER stress (ERS) sensor BiP is significantly upregulated in patients with bile reflux-associated IM. In a deoxycholic acid (DCA)-induced IM model using INS-GAS mice, pharmacological inhibition of IRE1α attenuated gastric mucosal injury and metaplastic progression. Mechanistically, we demonstrate that the mitochondrial chaperone HSPA9 acts as a critical effector at mitochondria-associated membranes (MAMs). Activation of the BiP-IRE1α-XBP1 axis upregulated HSPA9, facilitating excessive ER-to-mitochondria Ca2+ transfer. This calcium overload triggered mitochondrial dysfunction and oxidative stress, driving gastric epithelial transdifferentiation. Furthermore, network pharmacology identified quercetin as a novel BiP inhibitor. We validated that quercetin stabilizes BiP conformation, suppresses the IRE1α-XBP1-HSPA9 signaling axis, and restores ER-mitochondrial Ca2+ homeostasis, thereby mitigating oxidative stress and alleviating DCA-induced IM. These findings unveil a pathogenic ER-mitochondria signaling axis and highlight HSPA9 as a potential therapeutic target, suggesting quercetin as a promising chemopreventive strategy for intercepting GC progression.

Keywords:  Endoplasmic reticulum stress; Gastric intestinal metaplasia; HSPA9; Mitochondrial dysfunction; Quercetin

DOI:  https://doi.org/10.1016/j.freeradbiomed.2026.03.010
Biochem Pharmacol. 2026 Feb 27. pii: S0006-2952(26)00181-4. [Epub ahead of print]248 117850

USP30 alleviates intestinal ischemia-reperfusion injury by deubiquitinating MFN2 mediating the mitochondrial endoplasmic reticulum pathway.

Ziyi Weng, Tulanisa Kadier, Ruili Ding, Yu Shi, Jingyuan Xie, Rong Chen, Qingtao Meng.

  Intestinal ischemia-reperfusion (IIR) injury can cause intestinal barrier damage, systemic inflammatory response, and high mortality. The key mechanism is the disorder of the mitochondrial-endoplasmic reticulum network. Ubiquitin-specific peptidase 30 (USP30), located on the outer mitochondrial membrane, can reverse the partial ubiquitination of Parkin substrates or completely remove the ubiquitin chain to maintain mitochondrial function. Mitofusin 2 (MFN2) is a mitochondrial outer membrane fusion protein that mediates mitophagy and endoplasmic reticulum stress and participates in the formation of mitochondria-associated endoplasmic reticulum (MAMs). Our research showed that IIR reduces the protein expression of USP30 and MFN2, and overexpression of USP30 can increase the stability of MFN2 through deubiquitination and alleviate the damage caused by IIR. After overexpression of MFN2, mitochondrial dysfunction and endoplasmic reticulum stress caused by IIR are restored, while knockdown of MFN2 weakens the protective effect of USP30 on the MAMs. USP30 alleviates endoplasmic reticulum stress and mitochondrial dysfunction caused by intestinal ischemia-reperfusion injury by reducing the ubiquitination level of MFN2. The regulation of USP30 may be a promising strategy for alleviating intestinal ischemia-reperfusion injury.

Keywords:  Endoplasmic reticulum stress; Intestinal ischemia-reperfusion; MAMs; MFN2; Mitochondrial dysfunction; USP30

DOI:  https://doi.org/10.1016/j.bcp.2026.117850
J Cell Sci. 2026 Mar 01. pii: jcs264310. [Epub ahead of print]139(5):

Unconventional model organisms bend our view on mitochondrial cristae.

Silvia Tassan-Lugrezin, Silje A C A Debets, Laura van Niftrik, Taco W A Kooij, Irina Bregy.

  Cristae, convolutions of the inner mitochondrial membrane, provide an extended surface area for respiratory chain complexes and ATP synthases. Crista structure has been extensively researched in opisthokont model organisms, such as yeast and various animals; however, the vast majority of eukaryotic cristae diversity has been largely unexplored. Here, we provide a comprehensive overview of crista formation and maintenance in Euglenozoa and Alveolata, two highly divergent eukaryotic clades that include parasites of clinical and veterinary importance. Within these clades, cristae have been studied primarily in the kinetoplastid Trypanosoma brucei and the apicomplexan Toxoplasma gondii. We also discuss the apicomplexan Plasmodium falciparum, the deadliest human parasite and etiological agent of malaria, in which de novo formation of cristae occurs naturally following an apparently acristate life cycle stage. We compare findings from these divergent and disease-relevant organisms with those from more traditional model organisms, highlighting conserved and unique traits across the eukaryotic kingdom. In this Review, we focus on the roles of three key players in crista curvature - ATP synthase, the mitochondrial contact site and cristae organizing system (MICOS) and cardiolipin, a lipid specific to the inner mitochondrial membrane. By comparing distantly related organisms, we synthesize a broadly applicable model of the general principles of crista formation.

Keywords:   Plasmodium falciparum ; Toxoplasma gondii ; Trypanosoma brucei ; ATP synthase; Apicomplexa; Cardiolipin; Kinetoplastida; MICOS; Mitochondrial cristae

DOI:  https://doi.org/10.1242/jcs.264310