bims-lysosi 2022-05-01 papers

bims-lysosi

Biomed News

on Lysosomes and signaling

Issue of 2022–05–01
29 papers selected by
Stephanie Fernandes, Max Planck Institute for Biology of Ageing

Coordinated conformational changes in the V1 complex during V-ATPase reversible dissociation.
Axonal transport of late endosomes and amphisomes is selectively modulated by local Ca2+ efflux and disrupted by PSEN1 loss of function.
Mutations in V-ATPase in follicular lymphoma activate autophagic flux creating a targetable dependency.
Dynein is required for Rab7-dependent endosome maturation, retrograde dendritic transport, and degradation.
CROP: a retromer-PROPPIN complex mediating membrane fission in the endo-lysosomal system.
Glutamine, MTOR and autophagy: a multiconnection relationship.
Essential role of lysosomal Ca2+-mediated TFEB activation in mitophagy and functional adaptation of pancreatic β-cells to metabolic stress.
Asteltoxin inhibits extracellular vesicle production through AMPK/mTOR-mediated activation of lysosome function.
HexA-Enzyme Coated Polymer Nanoparticles for the Development of a Drug-Delivery System in the Treatment of Sandhoff Lysosomal Storage Disease.
Overexpression of progranulin increases pathological protein accumulation by suppressing autophagic flux.
Impact of α-synuclein fibrillar strains and ß-amyloid assemblies on mouse cortical neurons endo-lysosomal logistics.
Misfolded GBA/β-glucocerebrosidase impairs ER-quality control by chaperone-mediated autophagy in Parkinson disease.
The TORC1 phosphoproteome in C. elegans reveals roles in transcription and autophagy.
Acetylation of SCFD1 regulates SNARE complex formation and autophagosome-lysosome fusion.
β-Cell Succinate Dehydrogenase Deficiency Triggers Metabolic Dysfunction and Insulinopenic Diabetes.
Neurophysiological functions and pharmacological tools of acidic and non-acidic Ca2+ stores.
Interphase chromosome condensation in nutrient-starved conditions requires Cdc14 and Hmo1, but not condensin, in yeast.
Targeting impaired autophagy as a therapeutic strategy for Koolen-de Vries syndrome.
Increased mTORC2 pathway activation in lymph nodes of iMCD-TAFRO.
Neuronal mTOR Outposts: Implications for Translation, Signaling, and Plasticity.
S-Nitrosylation of cathepsin B affects autophagic flux and accumulation of protein aggregates in neurodegenerative disorders.
Correlative Organelle Microscopy: Fluorescence Guided Volume Electron Microscopy of Intracellular Processes.
Adult-Onset Neuronal Ceroid Lipofuscinosis With a Novel DNAJC5 Mutation Exhibits Aberrant Protein Palmitoylation.
Blocking ribosomal protein S6 phosphorylation inhibits podocyte hypertrophy and focal segmental glomerulosclerosis.
FCHO controls AP2's initiating role in endocytosis through a PtdIns(4,5)P2-dependent switch.
Cytokine profile and cholesterol levels in patients with Niemann-Pick type C disease presenting neurological symptoms: The in vivo effect of miglustat and the in vitro effect of N-acetylcysteine and Coenzyme Q10.
Kinase-independent synthesis of 3-phosphorylated phosphoinositides by a phosphotransferase.
Rab22a promotes the proliferation, migration, and invasion of lung adenocarcinoma via up-regulating PI3K/Akt/mTOR signaling pathway.
Phosphoinositide phosphorylation sans kinase.

Nat Struct Mol Biol. 2022 Apr 25.

Coordinated conformational changes in the V1 complex during V-ATPase reversible dissociation.

Thamiya Vasanthakumar, Kristine A Keon, Stephanie A Bueler, Michael C Jaskolka, John L Rubinstein.

Vacuolar-type ATPases (V-ATPases) are rotary enzymes that acidify intracellular compartments in eukaryotic cells. These multi-subunit complexes consist of a cytoplasmic V1 region that hydrolyzes ATP and a membrane-embedded VO region that transports protons. V-ATPase activity is regulated by reversible dissociation of the two regions, with the isolated V1 and VO complexes becoming autoinhibited on disassembly and subunit C subsequently detaching from V1. In yeast, assembly of the V1 and VO regions is mediated by the regulator of the ATPase of vacuoles and endosomes (RAVE) complex through an unknown mechanism. We used cryogenic-electron microscopy of yeast V-ATPase to determine structures of the intact enzyme, the dissociated but complete V1 complex and the V1 complex lacking subunit C. On separation, V1 undergoes a dramatic conformational rearrangement, with its rotational state becoming incompatible for reassembly with VO. Loss of subunit C allows V1 to match the rotational state of VO, suggesting how RAVE could reassemble V1 and VO by recruiting subunit C.

DOI: https://doi.org/10.1038/s41594-022-00757-z
Sci Adv. 2022 Apr 29. 8(17): eabj5716

Axonal transport of late endosomes and amphisomes is selectively modulated by local Ca2+ efflux and disrupted by PSEN1 loss of function.

Pearl P Y Lie, Lang Yoo, Chris N Goulbourne, Martin J Berg, Philip Stavrides, Chunfeng Huo, Ju-Hyun Lee, Ralph A Nixon.

Dysfunction and mistrafficking of organelles in autophagy- and endosomal-lysosomal pathways are implicated in neurodegenerative diseases. Here, we reveal selective vulnerability of maturing degradative organelles (late endosomes/amphisomes) to disease-relevant local calcium dysregulation. These organelles undergo exclusive retrograde transport in axons, with occasional pauses triggered by regulated calcium efflux from agonist-evoked transient receptor potential cation channel mucolipin subfamily member 1 (TRPML1) channels-an effect greatly exaggerated by exogenous agonist mucolipin synthetic agonist 1 (ML-SA1). Deacidification of degradative organelles, as seen after Presenilin 1 (PSEN1) loss of function, induced pathological constitutive "inside-out" TRPML1 hyperactivation, slowing their transport comparably to ML-SA1 and causing accumulation in dystrophic axons. The mechanism involved calcium-mediated c-Jun N-terminal kinase (JNK) activation, which hyperphosphorylated dynein intermediate chain (DIC), reducing dynein activity. Blocking TRPML1 activation, JNK activity, or DIC1B serine-80 phosphorylation reversed transport deficits in PSEN1 knockout neurons. Our results, including features demonstrated in Alzheimer-mutant PSEN1 knockin mice, define a mechanism linking dysfunction and mistrafficking in lysosomal pathways to neuritic dystrophy under neurodegenerative conditions.

DOI: https://doi.org/10.1126/sciadv.abj5716
Autophagy. 2022 Apr 28.

Mutations in V-ATPase in follicular lymphoma activate autophagic flux creating a targetable dependency.

Fangyang Wang, Ying Yang, Daniel J Klionsky, Sami N Malek.

  The recent discovery of recurrent gene mutations in chaperones or components of the vacuolar-type H+-translocating ATPase (V-ATPase) in follicular lymphoma (FL) was an unexpected finding. The application of whole exome sequencing and targeted gene re-sequencing has resulted in the identification of mutations in ATP6AP1, ATP6V1B2 and VMA21 in a combined 30% of FL, together constituting a major novel mutated pathway in this disease. Interestingly, no other human hematological malignancy carries these mutations at more than sporadic occurrences, implicating unique aspects of FL biology requiring these mutations. The mutations in ATP6V1B2 and VMA21 through separate mechanisms impair lysosomal V-ATPase activity resulting in an elevated lysosomal pH. The elevated lysosomal pH impairs protein and peptide hydrolysis and associates with reduced cytoplasmic amino acid concentrations resulting in compensatory activation of autophagic flux. The elevated autophagic flux constitutes a survival dependency for FL cells and can be targeted with inhibitors to ULK1 and multiple recently identified cyclin dependent kinase inhibitors. Targeting autophagy alone or in combination with other targeted therapies constitutes a novel therapeutic opportunity for FL patients.

Keywords:  Autophagy; cancer; disease; therapeutics; tumor

DOI:  https://doi.org/10.1080/15548627.2022.2071382
J Neurosci. 2022 Apr 26. pii: JN-RM-2530-21. [Epub ahead of print]

Dynein is required for Rab7-dependent endosome maturation, retrograde dendritic transport, and degradation.

Chan Choo Yap, Laura Digilio, Lloyd P McMahon, Tuanlao Wang, Bettina Winckler.

In all cell types, endocytosed cargo is transported along a set of endosomal compartments, which are linked maturationally from early endosomes (EE) via late endosomes (LE) to lysosomes. Lysosomes are critical for degradation of proteins that enter through endocytic as well as autophagic pathways. Rab7 is the master regulator of early-to-late endosome maturation, motility, and fusion with lysosomes. We previously showed that most degradative lysosomes are localized in the soma and in the first 25 µm of the dendrite and that bulk degradation of dendritic membrane proteins occurs in/near the soma. Dendritic late endosomes therefore move retrogradely in a Rab7-dependent manner for fusion with somatic lysosomes. We now used cultured E18 rat hippocampal neurons of both sexes to determine which microtubule motor is responsible for degradative flux of late endosomes. Based on multiple approaches (inhibiting dynein/dynactin itself or inhibiting dynein recruitment to endosomes by expressing the C-terminus of the Rab7 effector, RILP), we now demonstrate that net retrograde flux of late endosomes in dendrites is supported by dynein. Inhibition of dynein also delays maturation of somatic endosomes, as evidenced by excessive accumulation of Rab7. In addition, degradation of dendritic cargos is inhibited. Our results also suggest that GDP-GTP cycling of Rab7 appears necessary not only for endosomal maturation but also for fusion with lysosomes subsequent to arrival in the soma. In conclusion, Rab7-dependent dynein/dynactin recruitment to dendritic endosomes plays multifaceted roles in dendritic endosome maturation as well as retrograde transport of late endosomes to sustain normal degradative flux.Significance StatementLysosomes are critical for degradation of membrane and extracellular proteins that enter through endocytosis. Lysosomes are also the endpoint of autophagy and thus responsible for protein and organelle homeostasis. Endosomal-lysosomal dysfunction is linked to neurodegeneration and aging. We identify roles in dendrites for two proteins with links to human diseases, Rab7 and dynein. Our previous work identified a process that requires directional retrograde transport in dendrites, namely efficient degradation of short-lived membrane proteins. Based on multiple approaches, we demonstrate that Rab7-dependent recruitment of dynein motors supports net retrograde transport to lysosomes and is needed for endosome maturation. Our data also suggest that GDP-GTP cycling of Rab7 is required for fusion with lysosomes and degradation, subsequent to arrival in the soma.

DOI: https://doi.org/10.1523/JNEUROSCI.2530-21.2022
EMBO J. 2022 Apr 25. e109646

CROP: a retromer-PROPPIN complex mediating membrane fission in the endo-lysosomal system.

Thibault Courtellemont, Maria Giovanna De Leo, Navin Gopaldass, Andreas Mayer.

  Endo-lysosomal compartments exchange proteins by fusing, fissioning, and through endosomal transport carriers. Thereby, they sort many plasma membrane receptors and transporters and control cellular signaling and metabolism. How the membrane fission events are catalyzed is poorly understood. Here, we identify the novel CROP complex as a factor acting at this step. CROP joins members of two protein families: the peripheral subunits of retromer, a coat forming endosomal transport carriers, and membrane inserting PROPPINs. Integration into CROP potentiates the membrane fission activity of the PROPPIN Atg18 on synthetic liposomes and confers strong preference for binding PI(3,5)P2 , a phosphoinositide required for membrane fission activity. Disrupting CROP blocks fragmentation of lysosome-like yeast vacuoles in vivo. CROP-deficient mammalian endosomes accumulate micrometer-long tubules and fail to export cargo, suggesting that carriers attempt to form but cannot separate from these organelles. PROPPINs compete for retromer binding with the SNX-BAR proteins, which recruit retromer to the membrane during the formation of endosomal carriers. Transition from retromer-SNX-BAR complexes to retromer-PROPPIN complexes might hence switch retromer activities from cargo capture to membrane fission.

Keywords:  autophagy; endosomes; lysosomes; retromer; yeast

DOI:  https://doi.org/10.15252/embj.2021109646
Autophagy. 2022 Apr 26. 1-2

Glutamine, MTOR and autophagy: a multiconnection relationship.

Clément Bodineau, Mercedes Tomé, Piedad Del Socorro Murdoch, Raúl V Durán.

  Cancer cells metabolize glutamine mostly through glutaminolysis, a metabolic pathway that activates MTORC1. The AMPK-MTORC1 signaling axis is a key regulator of cell growth and proliferation. Our recent investigation identified that the connection between glutamine and AMPK is not restricted to glutaminolysis. Rather, we demonstrated the crucial role of ASNS (asparagine synthetase (glutamine-hydrolyzing)) and the GABA shunt for the metabolic control of the AMPK-MTORC1 axis during glutamine sufficiency. Our results elucidated a metabolic network by which glutamine metabolism regulates the MTORC1-macroautophagy/autophagy pathway through two independent branches involving glutaminolysis and ASNS-GABA shunt.

Keywords:  ASNS; GABA-shunt; MTORC1; glutamine; glutamoptosis

DOI:  https://doi.org/10.1080/15548627.2022.2062875
Autophagy. 2022 Apr 25.

Essential role of lysosomal Ca2+-mediated TFEB activation in mitophagy and functional adaptation of pancreatic β-cells to metabolic stress.

Kihyoun Park, Myung-Shik Lee.

  Although the role of pancreatic β-cell macroautophagy/autophagy is well known, that of β-cell mitophagy is unclear. We investigated the changes of lysosomal Ca2+ by mitochondrial or metabolic stress that can modulate TFEB activation and, additionally, the role of TFEB-induced mitophagy in β-cell function. Mitochondrial or metabolic stress induces mitophagy, which is mediated by lysosomal Ca2+ release, increased cytosolic [Ca2+] and subsequent TFEB activation. Lysosomal Ca2+ release is replenished by ER→lysosome Ca2+ refilling through ER Ca2+ exit channels, which is important for the increase of cytosolic [Ca2+] and mitophagy by mitochondria stressors. High-fat diet (HFD) feeding augments pancreatic β-cell mitophagy, probably as an adaptation to metabolic stress. HFD-induced increase of β-cell mitophagy is reduced by tfeb KO, leading to increased ROS and decreased mitochondrial complex activity or oxygen consumption in tfeb-KO islets. In tfeb Δβ-cell mice, HFD-induced glucose intolerance and β-cell dysfunction are aggravated. Expression of mitophagy receptor genes including Optn or Calcoco2 is increased by mitochondrial or metabolic stressors in a TFEB-dependent manner, likely contributing to increased mitophagy. These results suggest that lysosomal Ca2+ release in conjunction with ER→lysosome Ca2+ refilling is important for TFEB activation and mitophagy induction, which contributes to pancreatic β-cell adaptation to metabolic stress.

Keywords:  Ca2+; TFEB; lysosome; mitophagy; pancreatic β-cells

DOI:  https://doi.org/10.1080/15548627.2022.2069956
Sci Rep. 2022 Apr 23. 12(1): 6674

Asteltoxin inhibits extracellular vesicle production through AMPK/mTOR-mediated activation of lysosome function.

Fumie Mitani, Jianyu Lin, Tatsuya Sakamoto, Ryo Uehara, Tomoya Hikita, Takuya Yoshida, Andi Setiawan, Masayoshi Arai, Chitose Oneyama.

Cancer cells secrete aberrantly large amounts of extracellular vesicles (EVs) including exosomes, which originate from multivesicular bodies (MVBs). Because EVs potentially contribute to tumor progression, EV inhibitors are of interest as novel therapeutics. We screened a fungal natural product library. Using cancer cells engineered to secrete luciferase-labeled EVs, we identified asteltoxin, which inhibits mitochondrial ATP synthase, as an EV inhibitor. Low concentrations of asteltoxin inhibited EV secretion without inducing mitochondrial damage. Asteltoxin attenuated cellular ATP levels and induced AMPK-mediated mTORC1 inactivation. Consequently, MiT/TFE transcription factors are translocated into the nucleus, promoting transcription of lysosomal genes and lysosome activation. Electron microscopy analysis revealed that the number of lysosomes increased relative to that of MVBs and the level of EVs decreased after treatment with asteltoxin or rapamycin, an mTORC1 inhibitor. These findings suggest that asteltoxin represents a new type of EV inhibitor that controls MVB fate.

DOI: https://doi.org/10.1038/s41598-022-10692-0
J Funct Biomater. 2022 Mar 31. pii: 37. [Epub ahead of print]13(2):

HexA-Enzyme Coated Polymer Nanoparticles for the Development of a Drug-Delivery System in the Treatment of Sandhoff Lysosomal Storage Disease.

Eleonora Calzoni, Alessio Cesaretti, Nicolò Montegiove, Alessandro Di Michele, Roberto Maria Pellegrino, Carla Emiliani.

  Lysosomal storage disorders (LSDs) are a set of metabolic diseases caused by mutations in genes that are in charge of the production of lysosomal enzymes, resulting in the buildup of non-degraded substrates and the consequent systemic damage that mainly involves the Central Nervous System (CNS). One of the most widely used and studied treatments is Enzyme Replacement Therapy, which is based on the administration of the recombinant deficient enzyme. This strategy has often proved fallacious due to the enzyme instability in body fluids and its inability to reach adequate levels in the CNS. In this work, we developed a system based on nanotechnology that allows a stable enzyme to be obtained by its covalent immobilization on nanoparticles (NPs) of polylactic acid, subsequently administered to a cellular model of LSDs, i.e., Sandhoff disease, caused by the absence or deficiency of the β-d-N-acetyl-hexosaminidase A (HexA) enzyme. The HexA enzymes, loaded onto the polymeric NPs through an immobilization procedure that has already been investigated and validated, were found to be stable over time, maintain optimal kinetic parameters, be able to permeate the plasma membrane, hydrolyze HexA's natural substrate, and restore enzyme activity close to the levels of healthy cells. These results thus lay the foundation for testing the HexA-NPs in animal models of the disease and thus obtaining an efficient drug-delivery system.

Keywords:  Sandhoff disease; biopolymer nanoparticles; covalent immobilization; enzyme replacement therapy; ganglioside degradation; lysosomal storage disorders; restored activity

DOI:  https://doi.org/10.3390/jfb13020037
Biochem Biophys Res Commun. 2022 Apr 16. pii: S0006-291X(22)00593-9. [Epub ahead of print]611 78-84

Overexpression of progranulin increases pathological protein accumulation by suppressing autophagic flux.

Yoshinori Tanaka, Shun-Ya Kusumoto, Yuki Honma, Kosuke Takeya, Masumi Eto.

  Progranulin (PGRN) haploinsufficiency from autosomal dominant mutations in the PGRN gene causes frontotemporal lobar degeneration, which is characterized by cytoplasmic inclusions predominantly containing TDP-43 (FTLD-TDP). PGRN supplementation for patients with a PGRN gene mutation has recently been proposed as a therapeutic strategy to suppress FTLD-TDP. However, it currently remains unclear whether excessive amounts of PGRN are beneficial or harmful. We herein report the effects of PGRN overexpression on autophagic flux in a cultured cell model. PGRN overexpression increased the level of an autophagosome marker without promoting autophagosome formation and decreased the signal intensity of an autolysosome marker, indicating the suppression of autophagic flux due to reductions in the formation of autolysosomes. Assessments of lysosome numbers and biogenesis using LysoTracker and cells stably expressing TFEB-GFP, respectively, indicated that PGRN overexpression increased the lysosome numbers without lysosomal biogenesis. These results suggest that PGRN overexpression suppressed autophagic flux by inhibiting autophagosome-lysosome fusion. Moreover, PGRN overexpression enhanced polyglutamine aggregation and aggregate-prone TDP-43 accumulation, indicating that the suppression of autophagic flux by excessive amounts of PGRN worsens the pathology of neurodegenerative diseases.

Keywords:  Autophagic flux; Lysosome biogenesis; Progranulin; TDP-43

DOI:  https://doi.org/10.1016/j.bbrc.2022.04.064
eNeuro. 2022 Apr 25. pii: ENEURO.0227-21.2022. [Epub ahead of print]

Impact of α-synuclein fibrillar strains and ß-amyloid assemblies on mouse cortical neurons endo-lysosomal logistics.

Qiao-Ling Chou, Ania Alik, François Marquier, Ronald Melki, François Treussart, Michel Simonneau.

  Endosomal transport and positioning cooperate in the establishment of neuronal compartment architecture, dynamics and function, contributing to neuronal intracellular logistics. Furthermore, dysfunction of endo-lysosomal has been identified as a common mechanism in neurodegenerative diseases. Here, we analyzed endo-lysosomal transport when α-synuclein (α-syn) fibrillar polymorphs, ß-amyloid (Aß) fibrils and oligomers were externally applied on primary cultures of mouse cortical neurons. To measure this transport, we used a simple readout based on the spontaneous endocytosis in cultured neurons of fluorescent nanodiamonds, a perfectly stable nano-emitter, and the subsequent automatic extraction and quantification of their directed motions at high-throughput. α-syn fibrillar polymorphs, Aß fibrils and oligomers induce a two-fold decrease of the fraction of nanodiamonds transported along microtubules, while only slightly reducing their interaction with cortical neurons. This important decrease in moving endosomes is expected to have a huge impact on neuronal homeostasis. We next assessed lysosomes dynamics, using Lysotracker. Neurons exposure to Aß oligomers led to an increase in the number of lysosomes, a decrease in the fraction of moving lysosome and an increase in their size, reminiscent of that found in APP transgenic model of Alzheimer's disease. We then analyzed the effect of α-syn fibrillar polymorphs, Aß fibrils and oligomers on endosomal and lysosomal transport and quantified directed transport of those assemblies within cortical neurons. We report different impacts on endosomal and lysosomal transport parameters and differences in the trajectory lengths of cargoes loaded with pathogenic protein assemblies. Our results suggest that intraneuronal pathogenic protein aggregates internalization and transport may represent a target for novel neuroprotective therapeutic strategies.Significance StatementNeurodegenerative diseases (NDs) are characterized by the deposition of protein aggregates. These proteins exert a broad range of neuronal toxicity. Defects in endo-lysosomal traffic are increasingly viewed as key pathological features of NDs, likely contributing to synaptic dysfunction and ultimately neuronal death. Here we measured by fast fluorescence videomicroscopy the endosomal and lysosomal dynamics in the branches of primary culture of mouse cortical neurons after externally applying α-syn fibrillar polymorphs (fibrils and ribbons) and Aß assemblies (oligomers and fibrils). We provide significant insight into the differential effects of these pathogenic protein assemblies on endosomal and lysosomal transport, and also reveal distinct transport characteristics of the compartments loaded with these protein assemblies compared to endosome ones.

Keywords:  alpha-synuclein; beta-amyloid assemblies; endosome; intraneuronal transport; lysosome; mouse cortical neuron

DOI:  https://doi.org/10.1523/ENEURO.0227-21.2022
Autophagy. 2022 Apr 28.

Misfolded GBA/β-glucocerebrosidase impairs ER-quality control by chaperone-mediated autophagy in Parkinson disease.

Sheng-Han Kuo, Inmaculada Tasset, Ana Maria Cuervo, David Sulzer.

  Inhibition of chaperone-mediated autophagy (CMA), a selective type of lysosomal degradation for intracellular proteins, may contribute to pathogenesis in neurodegenerative diseases including Parkinson disease (PD). Pathogenic variants of PD-related proteins that reside in the cytosol, including SNCA/alpha-synuclein, LRRK2 (leucine rich repeat kinase 2), UCHL1 (ubiquitin Cterminal hydrolase 1) and VPS35 (VPS35 retromer complex component), exert inhibitory effects on CMA. Decreased CMA activity has also been reported in sporadic PD patients, consistent with an association between CMA inhibition and PD. We have now reported the first example of CMA dysfunction caused by a non-cytosolic PD-related protein, GBA/β-glucocerebrosidase, the most common genetic risk factor for PD, which uncovers a new role for CMA in endoplasmic reticulum (ER) quality control.

Keywords:  Chaperones; ER quality control; lysosomal enzymes; lysosomes; neurodegeneration; protein aggregation; protein trafficking; proteotoxicity

DOI:  https://doi.org/10.1080/15548627.2022.2071383
iScience. 2022 May 20. 25(5): 104186

The TORC1 phosphoproteome in C. elegans reveals roles in transcription and autophagy.

Aileen K Sewell, Zachary C Poss, Christopher C Ebmeier, Jeremy R Jacobsen, William M Old, Min Han.

  The protein kinase complex target of rapamycin complex 1 (TORC1) is a critical mediator of nutrient sensing that has been widely studied in cultured cells and yeast, yet our understanding of the regulatory activities of TORC1 in the context of a whole, multi-cellular organism is still very limited. Using Caenorhabditis elegans, we analyzed the DAF-15/Raptor-dependent phosphoproteome by quantitative mass spectrometry and characterized direct kinase targets by in vitro kinase assays. Here, we show new targets of TORC1 that indicate previously unknown regulation of transcription and autophagy. Our results further show that DAF-15/Raptor is differentially expressed during postembryonic development, suggesting a dynamic role for TORC1 signaling throughout the life span. This study provides a comprehensive view of the TORC1 phosphoproteome, reveals more than 100 DAF-15/Raptor-dependent phosphosites that reflect the complex function of TORC1 in a whole, multi-cellular organism, and serves as a rich resource to the field.

Keywords:  Cell biology; Developmental biology; Functional aspects of cell biology; Omics; Proteomics

DOI:  https://doi.org/10.1016/j.isci.2022.104186
Autophagy. 2022 Apr 24. 1-15

Acetylation of SCFD1 regulates SNARE complex formation and autophagosome-lysosome fusion.

Hong Huang, Qinqin Ouyang, Kunrong Mei, Ting Liu, Qiming Sun, Wei Liu, Rong Liu.

  SCFD1 (sec1 family domain containing 1) was recently shown to function in autophagosome-lysosome fusion, and multiple studies have demonstrated the regulatory impacts of acetylation (a post-translational modification) on macroautophagy/autophagy. Here, we demonstrate that both acetylation- and phosphorylation-dependent mechanisms control SCFD1's function in autophagosome-lysosome fusion. After detecting a decrease in the extent of SCFD1 acetylation under autophagy-stimulated conditions, we found that KAT2B/PCAF catalyzes the acetylation of residues K126 and K515 of SCFD1; we also showed that these two residues are deacetylated by SIRT4. Importantly, we showed that AMPK-controlled SCFD1 phosphorylation strongly disrupts the capacity of SCFD1 to interact with KAT2B, thus ensuring that the SCFD1 acetylation level remains low. Finally, we demonstrated that SCFD1 acetylation inhibits autophagic flux, specifically by blocking STX17-SNAP29-VAMP8 SNARE complex formation. Thus, our study reveals a mechanism through which phosphorylation and acetylation modifications of SCFD1 mediate SNARE complex formation to regulate autophagosome maturation.ACLY: ATP citrate lyase; CREB: cAMP responsive element binding protein; EBSS: nutrient-deprivation medium; EP300: E1A binding protein p300; KAT5/TIP60: lysine acetyltransferase 5; HOPS: homotypic fusion and protein sorting; MS: mass spectroscopy; SCFD1: sec1 family domain containing 1; SM: Sec1/Munc18; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; UVRAG: UV radiation resistance associated.

Keywords:  Autophagosome; SCFD1; SNARE; autophagy; lysosome

DOI:  https://doi.org/10.1080/15548627.2022.2064624
Diabetes. 2022 Apr 26. pii: db210834. [Epub ahead of print]

β-Cell Succinate Dehydrogenase Deficiency Triggers Metabolic Dysfunction and Insulinopenic Diabetes.

Sooyeon Lee, Haixia Xu, Aidan Van Vleck, Alex M Mawla, Albert Mao Li, Jiangbin Ye, Mark O Huising, Justin P Annes.

Mitochondrial dysfunction plays a central role in Type 2 Diabetes (T2D); however, the pathogenic mechanisms in pancreatic β-cells are incompletely elucidated. Succinate dehydrogenase (SDH) is a key mitochondrial enzyme with dual functions in the TCA cycle and electron transport chain (ETC). Using human diabetic samples and a mouse model of β-cell-specific SDH ablation (SDHBβKO), we define SDH deficiency as a driver of mitochondrial dysfunction in β-cell failure and insulinopenic diabetes. β-Cell SDH deficiency impairs glucose-induced respiratory oxidative phosphorylation and mitochondrial membrane potential (ΔΨm) collapse, thereby compromising glucose-stimulated ATP production, insulin secretion and β-cell growth. Mechanistically, metabolomic and transcriptomic studies reveal that the loss of SDH causes excess succinate accumulation, which inappropriately activates mTORC1-regulated metabolic anabolism, including increased SREBP-regulated lipid synthesis. These alterations, which mirror diabetes-associated human β-cell dysfunction, are partially reversed by acute mTOR inhibition with rapamycin. We propose SDH deficiency as a contributing mechanism to the progressive β-cell failure of diabetes and identify mTORC1 inhibition as a potential mitigation strategy.

DOI: https://doi.org/10.2337/db21-0834
Cell Calcium. 2022 Apr 10. pii: S0143-4160(22)00057-4. [Epub ahead of print]104 102582

Neurophysiological functions and pharmacological tools of acidic and non-acidic Ca2+ stores.

Lora L Martucci, José-Manuel Cancela.

Ca2+ signalling is of prime importance in controlling numerous cell functions in the brain. Endolysosomes are acidic organelles currently emerging as important Ca2+ stores in astrocytes, microglia, endothelial cells, and neurons. In neurons, these acidic Ca2+ stores are found in axons, soma, dendrites, and axon endings and could provide local sources of Ca2+ to control synaptic transmission, neuronal plasticity, and autophagy to name a few. This review will address how acidic Ca2+ stores are recruited in response to cell stimulation. We will focus on the role of the endolysosomal two-pore channels (TPCs) and their physiological agonist nicotinic acid adenine dinucleotide phosphate (NAADP) and how they interact with cyclic ADP-ribose and ryanodine receptors from the endoplasmic reticulum. Finally, this review will describe new pharmacological tools and animal mutant models now available to explore acidic Ca2+ stores as key elements in brain function and dysfunction.

DOI: https://doi.org/10.1016/j.ceca.2022.102582
Biochem Biophys Res Commun. 2022 Apr 20. pii: S0006-291X(22)00607-6. [Epub ahead of print]611 46-52

Interphase chromosome condensation in nutrient-starved conditions requires Cdc14 and Hmo1, but not condensin, in yeast.

Yuri Takeichi, Tsuneyuki Takuma, Kotaro Ohara, Most Naoshia Tasnin, Takashi Ushimaru.

  When asynchronously growing cells suffer from nutrient depletion and inactivation of target of rapamycin complex 1 (TORC1) protein kinase, the rDNA (rRNA gene) region is condensed in budding yeast Saccharomyces cerevisiae, which is executed by condensin and Cdc14 protein phosphatase. However, it is unknown whether these mitotic factors can condense the rDNA region in nutrient-starved interphase cells. Here, we show that condensin is not involved in TORC1 inactivation-induced rDNA condensation in G1 cells. Instead, the high-mobility group protein Hmo1 drove this process. The histone deacetylase Rpd3 and Cdc14, which repress rRNA transcription, were both required for the interphase rDNA condensation. Furthermore, interphase rDNA condensation necessitated CLIP and cohibin that tether rDNA to inner nuclear membranes. Finally, we showed that Hmo1, CLIP, Rpd3, and Cdc14 were required for survival in nutrient-starved G1 cells. Thus, this study disclosed novel features of interphase chromosome condensation.

Keywords:  Cdc14; Condensin; Hmo1; Interphase chromosome condensation; Ribosomal DNA (rDNA); Target of rapamycin complex 1 (TORC1)

DOI:  https://doi.org/10.1016/j.bbrc.2022.04.078
Autophagy. 2022 Apr 29. 1-3

Targeting impaired autophagy as a therapeutic strategy for Koolen-de Vries syndrome.

Ting Li, Ailing Li, Xin Pan.

  Koolen-de Vries syndrome (KdVS) is a genomic disorder characterized by intellectual disability, heart failure, hypotonia and congenital malformations, which is caused by haploinsufficiency of KANSL1. Because the pathogenesis of the disease is unknown, there is still no effective treatment. Here, we discuss our recent work identifying KANSL1 as an essential gene for macroautophagy/autophagy. We find that KANSL1 modulates autophagosome-lysosome fusion for cargo degradation by transcriptionally regulating Stx17 expression. Kansl1 heterozygous mice exhibit impaired neuronal and cardiac functions, resulting from the obstruction of autophagic clearance of damaged mitochondria and accumulation of reactive oxygen species in these tissues. Furthermore, we discovered an FDA-approved drug, 13-cis retinoic acid, is capable of alleviating these mitophagic defects and neurobehavioral abnormalities in Kansl1 heterozygous mice by promoting autophagosome-lysosome fusion via directly binding to STX17 and SNAP29. Our study provides the proof of concept to set up a link between KANSL1, autophagic defects and KdVS, and also proposes a therapeutic strategy for treatment of KdVS.

Keywords:  13-cis retinoic acid; KANSL1; STX17; autophagy; koolen-de Vries syndrome; mitochondria

DOI:  https://doi.org/10.1080/15548627.2022.2069904
J Cell Mol Med. 2022 Apr 30.

Increased mTORC2 pathway activation in lymph nodes of iMCD-TAFRO.

Alexis D Phillips, Joseph J Kakkis, Patricia Y Tsao, Sheila K Pierson, David C Fajgenbaum.

  Idiopathic multicentric Castleman disease (iMCD) is a rare and life-threatening haematologic disorder involving polyclonal lymphoproliferation and organ dysfunction due to excessive cytokine production, including interleukin-6 (IL-6). Clinical trial and real-world data demonstrate that IL-6 inhibition is effective in 34-50% of patients. mTOR, which functions through mTORC1 and mTORC2, is a recently discovered therapeutic target. The mTOR inhibitor sirolimus, which preferentially inhibits mTORC1, has led to sustained remission in a small cohort of anti-IL-6-refractory iMCD patients with thrombocytopenia, anasarca, fever, renal dysfunction and organomegaly (iMCD-TAFRO). However, sirolimus has not shown uniform effect, potentially due to its limited mTORC2 inhibition. To investigate mTORC2 activation in iMCD, we quantified the mTORC2 effector protein pNDRG1 by immunohistochemistry of lymph node tissue from six iMCD-TAFRO and eight iMCD patients who do not meet TAFRO criteria (iMCD-not-otherwise-specified; iMCD-NOS). mTORC2 activation was increased in all regions of iMCD-TAFRO lymph nodes and the interfollicular space of iMCD-NOS compared with control tissue. Immunohistochemistry also revealed increased pNDRG1 expression in iMCD-TAFRO germinal centres compared with autoimmune lymphoproliferative syndrome (ALPS), an mTOR-driven, sirolimus-responsive lymphoproliferative disorder, and comparable staining between iMCD-NOS and ALPS. These results suggest increased mTORC2 activity in iMCD and that dual mTORC1/mTORC2 inhibitors may be a rational therapeutic approach.

Keywords:  Castleman disease; TAFRO; autoimmune lymphoproliferative syndrome; iMCD; idiopathic multicentric Castleman disease; mTOR; mTORC2; pNDRG1

DOI:  https://doi.org/10.1111/jcmm.17251
Front Cell Neurosci. 2022 ;16 853634

Neuronal mTOR Outposts: Implications for Translation, Signaling, and Plasticity.

Bekir Altas, Andrea J Romanowski, Garrett W Bunce, Alexandros Poulopoulos.

  The kinase mTOR is a signaling hub for pathways that regulate cellular growth. In neurons, the subcellular localization of mTOR takes on increased significance. Here, we review findings on the localization of mTOR in axons and offer a perspective on how these may impact our understanding of nervous system development, function, and disease. We propose a model where mTOR accumulates in local foci we term mTOR outposts, which can be found in processes distant from a neuron's cell body. In this model, pathways that funnel through mTOR are gated by local outposts to spatially select and amplify local signaling. The presence or absence of mTOR outposts in a segment of axon or dendrite may determine whether regional mTOR-dependent signals, such as nutrient and growth factor signaling, register toward neuron-wide responses. In this perspective, we present the emerging evidence for mTOR outposts in neurons, their putative roles as spatial gatekeepers of signaling inputs, and the implications of the mTOR outpost model for neuronal protein synthesis, signal transduction, and synaptic plasticity.

Keywords:  axon; axon regeneration; ketamine; local translation; mTOR; ribosome biogenesis; synapse tagging

DOI:  https://doi.org/10.3389/fncel.2022.853634
Cell Death Differ. 2022 Apr 24.

S-Nitrosylation of cathepsin B affects autophagic flux and accumulation of protein aggregates in neurodegenerative disorders.

Ki-Ryeong Kim, Eun-Jung Cho, Jae-Won Eom, Sang-Seok Oh, Tomohiro Nakamura, Chang-Ki Oh, Stuart A Lipton, Yang-Hee Kim.

Protein S-nitrosylation is known to regulate enzymatic function. Here, we report that nitric oxide (NO)-related species can contribute to Alzheimer's disease (AD) by S-nitrosylating the lysosomal protease cathepsin B (forming SNO-CTSB), thereby inhibiting CTSB activity. This posttranslational modification inhibited autophagic flux, increased autolysosomal vesicles, and led to accumulation of protein aggregates. CA-074Me, a CTSB chemical inhibitor, also inhibited autophagic flux and resulted in accumulation of protein aggregates similar to the effect of SNO-CTSB. Inhibition of CTSB activity also induced caspase-dependent neuronal apoptosis in mouse cerebrocortical cultures. To examine which cysteine residue(s) in CTSB are S-nitrosylated, we mutated candidate cysteines and found that three cysteines were susceptible to S-nitrosylation. Finally, we observed an increase in SNO-CTSB in both 5XFAD transgenic mouse and flash-frozen postmortem human AD brains. These results suggest that S-nitrosylation of CTSB inhibits enzymatic activity, blocks autophagic flux, and thus contributes to AD pathogenesis.

DOI: https://doi.org/10.1038/s41418-022-01004-0
Front Cell Dev Biol. 2022 ;10 829545

Correlative Organelle Microscopy: Fluorescence Guided Volume Electron Microscopy of Intracellular Processes.

Sergey V Loginov, Job Fermie, Jantina Fokkema, Alexandra V Agronskaia, Cilia De Heus, Gerhard A Blab, Judith Klumperman, Hans C Gerritsen, Nalan Liv.

  Intracellular processes depend on a strict spatial and temporal organization of proteins and organelles. Therefore, directly linking molecular to nanoscale ultrastructural information is crucial in understanding cellular physiology. Volume or three-dimensional (3D) correlative light and electron microscopy (volume-CLEM) holds unique potential to explore cellular physiology at high-resolution ultrastructural detail across cell volumes. However, the application of volume-CLEM is hampered by limitations in throughput and 3D correlation efficiency. In order to address these limitations, we describe a novel pipeline for volume-CLEM that provides high-precision (<100 nm) registration between 3D fluorescence microscopy (FM) and 3D electron microscopy (EM) datasets with significantly increased throughput. Using multi-modal fiducial nanoparticles that remain fluorescent in epoxy resins and a 3D confocal fluorescence microscope integrated into a Focused Ion Beam Scanning Electron Microscope (FIB.SEM), our approach uses FM to target extremely small volumes of even single organelles for imaging in volume EM and obviates the need for post-correlation of big 3D datasets. We extend our targeted volume-CLEM approach to include live-cell imaging, adding information on the motility of intracellular membranes selected for volume-CLEM. We demonstrate the power of our approach by targeted imaging of rare and transient contact sites between the endoplasmic reticulum (ER) and lysosomes within hours rather than days. Our data suggest that extensive ER-lysosome and mitochondria-lysosome interactions restrict lysosome motility, highlighting the unique capabilities of our integrated CLEM pipeline for linking molecular dynamic data to high-resolution ultrastructural detail in 3D.

Keywords:  correlative light and electron microscopy; live-cell imaging; lysosome; organelle contact site; volume electron microscopy

DOI:  https://doi.org/10.3389/fcell.2022.829545
Front Aging Neurosci. 2022 ;14 829573

Adult-Onset Neuronal Ceroid Lipofuscinosis With a Novel DNAJC5 Mutation Exhibits Aberrant Protein Palmitoylation.

Qiang Huang, Yong-Fang Zhang, Lin-Jie Li, Eric B Dammer, Yong-Bo Hu, Xin-Yi Xie, Ran Tang, Jian-Ping Li, Jin-Tao Wang, Xiang-Qian Che, Gang Wang, Ru-Jing Ren.

  Neuronal ceroid lipofuscinosis (NCL) is composed of a group of inherited neurodegenerative diseases, with the hallmark of lipofuscin deposit (a mixture of lipids and proteins with metal materials) inside the lysosomal lumen, which typically emits auto-fluorescence. Adult-onset NCL (ANCL) has been reported to be associated with a mutation in the DNAJC5 gene, including L115R, L116Δ, and the recently identified C124_C133dup mutation. In this study, we reported a novel C128Y mutation in a young Chinese female with ANCL, and this novel mutation caused abnormal palmitoylation and triggered lipofuscin deposits.

Keywords:  adult-onset neuronal ceroid lipofuscinosis; cognitive decline; cysteine string protein α; lysosome; neurodegenerative disease

DOI:  https://doi.org/10.3389/fnagi.2022.829573
Kidney Int. 2022 Apr 25. pii: S0085-2538(22)00335-0. [Epub ahead of print]

Blocking ribosomal protein S6 phosphorylation inhibits podocyte hypertrophy and focal segmental glomerulosclerosis.

Fang Li, Yili Fang, Qiyuan Zhuang, Meichu Cheng, Desmond Moronge, Hao Jue, Oded Meyuhas, Xiaoqiang Ding, Zhigang Zhang, Jian-Kang Chen, Huijuan Wu.

  Ribosomal protein S6 (rpS6) phosphorylation mediates the hypertrophic growth of kidney proximal tubule cells. However, the role of rpS6 phosphorylation in podocyte hypertrophy and podocyte loss during the pathogenesis of focal segmental glomerulosclerosis (FSGS) remains undefined. Here, we examined rpS6 phosphorylation levels in kidney biopsy specimens from patients with FSGS and in podocytes from mouse kidneys with adriamycin-induced FSGS. Using genetic and pharmacologic approaches in the mouse model of FSGS, we investigated the role of rpS6 phosphorylation in podocyte hypertrophy and loss during development and progression of FSGS. Phosphorylated rpS6 was found to be markedly increased in the podocytes of patients with FSGS and adriamycin-induced FSGS in mice. Genetic deletion of the Tuberous sclerosis 1 gene in kidney glomerular podocytes activated mammalian target of rapamycin complex 1 signaling to rpS6 phosphorylation, resulting in podocyte hypertrophy and pathologic features similar to those of patients with FSGS including podocyte loss, leading to segmental glomerulosclerosis. Since protein phosphatase 1 is known to negatively regulate rpS6 phosphorylation; treatment with an inhibitor increased phospho-rpS6 levels, promoted podocyte hypertrophy and exacerbated formation of FSGS lesions. Importantly, blocking rpS6 phosphorylation (either by generating congenic rpS6 knock-in mice expressing non-phosphorylatable rpS6 or by inhibiting ribosomal protein S6 kinase 1-mediated rpS6 phosphorylation with an inhibitor) significantly blunted podocyte hypertrophy, inhibited podocyte loss, and attenuated formation of FSGS lesions. Thus, our study provides genetic and pharmacologic evidence indicating that specifically targeting rpS6 phosphorylation can attenuate the development of FSGS lesions by inhibiting podocyte hypertrophy and associated podocyte depletion.

Keywords:  focal segmental glomerulosclerosis (FSGS); podocyte hypertrophy; ribosomal protein S6 (rpS6)

DOI:  https://doi.org/10.1016/j.kint.2022.02.037
Sci Adv. 2022 Apr 29. 8(17): eabn2018

FCHO controls AP2's initiating role in endocytosis through a PtdIns(4,5)P2-dependent switch.

Nathan R Zaccai, Zuzana Kadlecova, Veronica Kane Dickson, Kseniya Korobchevskaya, Jan Kamenicky, Oleksiy Kovtun, Perunthottathu K Umasankar, Antoni G Wrobel, Jonathan G G Kaufman, Sally R Gray, Kun Qu, Philip R Evans, Marco Fritzsche, Filip Sroubek, Stefan Höning, John A G Briggs, Bernard T Kelly, David J Owen, Linton M Traub.

Clathrin-mediated endocytosis (CME) is the main mechanism by which mammalian cells control their cell surface proteome. Proper operation of the pivotal CME cargo adaptor AP2 requires membrane-localized Fer/Cip4 homology domain-only proteins (FCHO). Here, live-cell enhanced total internal reflection fluorescence-structured illumination microscopy shows that FCHO marks sites of clathrin-coated pit (CCP) initiation, which mature into uniform-sized CCPs comprising a central patch of AP2 and clathrin corralled by an FCHO/Epidermal growth factor potential receptor substrate number 15 (Eps15) ring. We dissect the network of interactions between the FCHO interdomain linker and AP2, which concentrates, orients, tethers, and partially destabilizes closed AP2 at the plasma membrane. AP2's subsequent membrane deposition drives its opening, which triggers FCHO displacement through steric competition with phosphatidylinositol 4,5-bisphosphate, clathrin, cargo, and CME accessory factors. FCHO can now relocate toward a CCP's outer edge to engage and activate further AP2s to drive CCP growth/maturation.

DOI: https://doi.org/10.1126/sciadv.abn2018
Exp Cell Res. 2022 Apr 26. pii: S0014-4827(22)00168-9. [Epub ahead of print] 113175

Cytokine profile and cholesterol levels in patients with Niemann-Pick type C disease presenting neurological symptoms: The in vivo effect of miglustat and the in vitro effect of N-acetylcysteine and Coenzyme Q10.

Tatiane G Hammerschmidt, Bruna Donida, Jéssica L Faverzani, Alana P Moura, Bianca G Dos Reis, Andryele Z Machado, Rejane G Kessler, Fernanda M Sebastião, Luiza S Reinhardt, Dinara J Moura, Carmen R Vargas.

  Niemann Pick type C is an inborn error of metabolism (IEM), classified as a lysosomal storage disease (LSD) caused by a dysfunction in NPC transport protein, that leads to intracellular accumulation of non-esterified cholesterol and other lipids. Clinical manifestations are ample, with visceral and neurological symptoms. Miglustat, a molecule that reversibly inhibits glucosylceramide synthase is used as treatment for this disorder. Studies demonstrated the influence of oxidative stress and inflammation in IEM, as well in animal model of NP-C disease. Nonetheless, literature lacks data on patients, so our work aimed to investigate if there is influence of chronic inflammation in the pathophysiology of NP-C disease, and the effect of miglustat, N-acetylcysteine (NAC) and Coenzyme Q10 (CoQ10). We evaluated the plasmatic cytokines in NPC patients at diagnosis and during the treatment with miglustat. Additionally, we performed an in vitro study with antioxidants NAC (1 mM and 2.5 mM) and CoQ10 (5 μM and 10 μM), where we could verify its effect on inflammatory parameters, as well as in cholesterol accumulation. Our results showed that NP-C patients have higher plasmatic levels of pro and anti-inflammatory cytokines (IL-6, IL-8, and IL-10) at diagnosis and the treatment with miglustat was able to restore it. In vitro study showed that treatment with antioxidants in higher concentrations significantly decrease cholesterol accumulation, and NAC at 2.5 mM normalized the level of pro-inflammatory cytokines. Although the mechanism is not completely clear, it can be related to restoration in lipid traffic and decrease in oxidative stress caused by antioxidants.

Keywords:  Coenzyme Q10; Inflammation; Lysosomal storage disease; Miglustat; N-Acetylcysteine; Niemann-Pick type C

DOI:  https://doi.org/10.1016/j.yexcr.2022.113175
Nat Cell Biol. 2022 Apr 28.

Kinase-independent synthesis of 3-phosphorylated phosphoinositides by a phosphotransferase.

Glenn F W Walpole, Jonathan Pacheco, Neha Chauhan, Jonathan Clark, Karen E Anderson, Yazan M Abbas, Danielle Brabant-Kirwan, Fernando Montaño-Rendón, Zetao Liu, Hongxian Zhu, John H Brumell, Alexander Deiters, Len R Stephens, Phillip T Hawkins, Gerald R V Hammond, Sergio Grinstein, Gregory D Fairn.

Despite their low abundance, phosphoinositides play a central role in membrane traffic and signalling. PtdIns(3,4,5)P3 and PtdIns(3,4)P2 are uniquely important, as they promote cell growth, survival and migration. Pathogenic organisms have developed means to subvert phosphoinositide metabolism to promote successful infection and their survival in host organisms. We demonstrate that PtdIns(3,4)P2 is a major product generated in host cells by the effectors of the enteropathogenic bacteria Salmonella and Shigella. Pharmacological, gene silencing and heterologous expression experiments revealed that, remarkably, the biosynthesis of PtdIns(3,4)P2 occurs independently of phosphoinositide 3-kinases. Instead, we found that the Salmonella effector SopB, heretofore believed to be a phosphatase, generates PtdIns(3,4)P2 de novo via a phosphotransferase/phosphoisomerase mechanism. Recombinant SopB is capable of generating PtdIns(3,4,5)P3 and PtdIns(3,4)P2 from PtdIns(4,5)P2 in a cell-free system. Through a remarkable instance of convergent evolution, bacterial effectors acquired the ability to synthesize 3-phosphorylated phosphoinositides by an ATP- and kinase-independent mechanism, thereby subverting host signalling to gain entry and even provoke oncogenic transformation.

DOI: https://doi.org/10.1038/s41556-022-00895-y
Exp Cell Res. 2022 Apr 26. pii: S0014-4827(22)00172-0. [Epub ahead of print] 113179

Rab22a promotes the proliferation, migration, and invasion of lung adenocarcinoma via up-regulating PI3K/Akt/mTOR signaling pathway.

Jinping Wang, Xue Luo, Jinxi Lu, Xi Wang, Yuan Miao, Qingchang Li, Liang Wang.

  Rab22a, a member of the proto-oncogene RAS family, belongs to the Rab5 subfamily. It participates in early endosome formation and regulates vesicle trafficking. The relationship between Rab22a and tumorigenesis remains elusive. In non-small cell lung cancer specimens, immunohistochemical staining showed consistently high expression of Rab22a in lung adenocarcinoma, but not in squamous cell carcinoma. In lung adenocarcinoma cell lines, A549 and H1299, transfection with Rab22a significantly promoted cell proliferation, migration, and invasion, whereas interference with Rab22a specific siRNA significantly inhibited the above capacities. Transfection with Rab22a also up-regulated the phosphorylation levels of core effector proteins on the PI3K/Akt/mTOR pathway. The Co-IP assay further confirmed the interaction between Rab22a and PI3Kp85α, the core regulatory subunit of PI3K. Application of rapamycin, the mTOR inhibitor, significantly reduced the upregulation of the proliferation, migration, and invasion abilities of lung adenocarcinoma cells transfected with Rab22a. These results suggest that Rab22a can promote the malignant phenotype of lung adenocarcinoma by upregulating the PI3K/Akt/mTOR signaling pathway, and may function as a potential anti-tumor therapeutic target.

Keywords:  Invasion; Lung adenocarcinoma; Migration; Rab22a; mTOR

DOI:  https://doi.org/10.1016/j.yexcr.2022.113179
Nat Cell Biol. 2022 Apr 28.

Phosphoinositide phosphorylation sans kinase.

Xiaofu Cao, Jeremy M Baskin.

DOI: https://doi.org/10.1038/s41556-022-00885-0