Translocon remodeling during protein synthesis at the ER
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ABSTRACT:
PROVIDER: PRJNA1265091 | ENA |
REPOSITORIES: ENA
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Project description:Protein biogenesis at the endoplasmic reticulum (ER) is coordinated by the Sec61 translocon whose dynamic subunit composition is essential for maintaining a functional proteome. How nascent secretory and membrane proteins recruit accessory factors to the translocon, and what controls the interplay between these factors during synthesis, is poorly understood. Here we use selective ribosome profiling to systematically define the cotranslational interactions of accessory factors for N-glycosylation (OST-A complex) and multipass membrane protein synthesis (GEL, PAT and BOS complexes). OST-A is actively recruited during translocation of long lumenal segments through an open Sec61 channel. This occurs independently of N-glycosylation acceptor sites, and is disfavored when Sec61 is closed. By contrast, the GEL, PAT and BOS complexes sample ribosomes docked at a closed Sec61 channel. Their recruitment is highly synchronized, and stabilized by newly inserted transmembrane domains (TMDs). Conversely, GEL, PAT and BOS binding is disfavored during translocation of long segments through open Sec61, or synthesis of long cytosolic segments. Analysis of large, topologically complex multipass proteins reveals that translocon composition can change repeatedly and reversibly during synthesis of a single polypeptide. These data establish a simple molecular logic underlying translocon remodeling during biogenesis of secretory and membrane proteins.
2025-08-30 | GSE297497 | GEO
Project description:The endoplasmic reticulum (ER) functions in protein and lipid synthesis, calcium ion flux, and inter-organelle communication, all of which are driven by the ER proteome landscape. ER is remodeled in part through autophagy-dependent protein turnover involving membrane-embedded ER-phagy receptors1,2. A refined tubular ER network is formed in neurons within highly polarized dendrites and axons3,4. Autophagy-deficient neurons in vivo display axonal ER accumulation within synaptic ER boutons, associated with hyper-excitability,5 and the ER-phagy receptor FAM134B has been genetically linked with human sensory and autonomic neuropathy6,7. However, mechanisms and receptor selectivity underlying ER remodeling by autophagy in neurons is limited. Here, we employ genetic, proteomic and computational tools to create a quantitative landscape of ER proteome remodeling via selective autophagy during conversion of stem cells to induced neurons in vitro. Through analysis of single and combinatorial ER-phagy receptor mutants coupled with an allelic series computational framework, we delineate the extent to which each of five receptors contributes to both the magnitude of ER turnover by autophagy and the selectivity of clearance for individual ER proteins. We define specific subsets of reticulon-domain containing ER-tubule shaping proteins or luminal proteins as preferred clients for autophagic turnover via distinct receptors. Using spatial sensors and flux reporters, we demonstrate receptor-specific autophagic capture of ER in axons, which correlates with aberrant accumulation of ER in axonal structures in ER-phagy receptor or autophagy-deficient cells. This molecular inventory of ER proteome remodeling and versatile genetic toolkit provides a quantitative framework for understanding the contributions of individual ER-phagy receptors for reshaping this critical organelle during transitions in cell states.
2024-01-08 | PXD046646 | Pride
Project description:The endoplasmic reticulum (ER) functions in protein and lipid synthesis, calcium ion flux, and inter-organelle communication, all of which are driven by the ER proteome landscape. ER is remodeled in part through autophagy-dependent protein turnover involving membrane-embedded ER-phagy receptors1,2. A refined tubular ER network is formed in neurons within highly polarized dendrites and axons3,4. Autophagy-deficient neurons in vivo display axonal ER accumulation within synaptic ER boutons, associated with hyper-excitability,5 and the ER-phagy receptor FAM134B has been genetically linked with human sensory and autonomic neuropathy6,7. However, mechanisms and receptor selectivity underlying ER remodeling by autophagy in neurons is limited. Here, we employ genetic, proteomic and computational tools to create a quantitative landscape of ER proteome remodeling via selective autophagy during conversion of stem cells to induced neurons in vitro. Through analysis of single and combinatorial ER-phagy receptor mutants coupled with an allelic series computational framework, we delineate the extent to which each of five receptors contributes to both the magnitude of ER turnover by autophagy and the selectivity of clearance for individual ER proteins. We define specific subsets of reticulon-domain containing ER-tubule shaping proteins or luminal proteins as preferred clients for autophagic turnover via distinct receptors. Using spatial sensors and flux reporters, we demonstrate receptor-specific autophagic capture of ER in axons, which correlates with aberrant accumulation of ER in axonal structures in ER-phagy receptor or autophagy-deficient cells. This molecular inventory of ER proteome remodeling and versatile genetic toolkit provides a quantitative framework for understanding the contributions of individual ER-phagy receptors for reshaping this critical organelle during transitions in cell states.
2024-01-08 | PXD041069 | Pride
Project description:Ribosome quality control activity potentiates vaccinia virus protein synthesis during infection
| PRJNA695555 | ENA
Project description:Translational regulation is of paramount importance for proteome remodeling during stem cell differentiation both at the global and transcript-specific level. In this study, we characterized translational remodeling during hepatogenic differentiation of induced pluripotent stem cells (iPSCs) by polysome profiling. We demonstrate that protein synthesis increases during the initial exit from pluripotency, but is then globally repressed during later steps of hepatogenic maturation. This global downregulation of translation is accompanied by a decrease in the protein abundance of components of the translation machinery, which involves a global reduction in translational efficiency of terminal oligopyrimidine tract (TOP) mRNA encoding translation-related factors. Despite global translational repression during hepatogenic differentiation, key hepatogenic genes remain efficiently translated, and the translation of several transcripts involved in hepato-specific functions and metabolic maturation are even induced. We conclude that, during hepatogenic differentiation, a global decrease in protein synthesis is accompanied by a specific translational rewiring towards hepato-specific transcripts.
2021-04-23 | GSE173106 | GEO
Project description:Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to various growth factors and cytokines including TGF- and TNF-, triggers ER tubulation by activating TAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/TAT1-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/TAT1 pathway may be a key target in ER stress and dysfunction.
2024-06-16 | PXD045865 | Pride
Project description:Endoplasmic reticulum (ER) plasticity and ER-phagy are intertwined processes essential for maintaining ER dynamics. We investigated the interplay between two isoforms of the ER-phagy receptor FAM134B in regulating ER remodeling in differentiating myoblasts. During myogenesis, the canonical FAM134B1 is degraded, while its isoform FAM134B2 is transcriptionally upregulated. The switch, favoring FAM134B2, indicates its significance as a regulator of ER morphology during myogenesis. FAM134B2 partial reticulon homology domain, with its rigid conformational characteristics, enables an efficient ER reshaping. FAM134B2 action increases in the active phase of differentiation leading to ER restructuring via ER-phagy, which then reverts to physiological levels when myotubes are mature and the ER reorganized. Knocking out both FAM134B isoforms in myotubes results in aberrant proteome landscape and the formation of dilated ER structures, both of which are rescued by FAM134B2 re-expression. Our results underscore how the fine tuning of FAM134B isoforms and ER-phagy orchestrate the ER dynamics during myogenesis providing insights into the molecular mechanisms governing ER homeostasis in muscle cells.
2024-12-27 | PXD053361 | Pride
Project description:Endoplasmic reticulum (ER) plasticity and ER-phagy are intertwined processes essential for maintaining ER dynamics. We investigated the interplay between two isoforms of the ER-phagy receptor FAM134B in regulating ER remodeling in differentiating myoblasts. During myogenesis, the canonical FAM134B1 is degraded, while its isoform FAM134B2 is transcriptionally upregulated. The switch, favoring FAM134B2, indicates its significance as a regulator of ER morphology during myogenesis. FAM134B2 partial reticulon homology domain, with its rigid conformational characteristics, enables an efficient ER reshaping. FAM134B2 action increases in the active phase of differentiation leading to ER restructuring via ER-phagy, which then reverts to physiological levels when myotubes are mature and the ER reorganized. Knocking out both FAM134B isoforms in myotubes results in aberrant proteome landscape and the formation of dilated ER structures, both of which are rescued by FAM134B2 re-expression. Our results underscore how the fine tuning of FAM134B isoforms and ER-phagy orchestrate the ER dynamics during myogenesis providing insights into the molecular mechanisms governing ER homeostasis in muscle cells.
2024-12-27 | PXD053358 | Pride
Project description:Proteostasis is essential for survival and particularly important for highly specialized post mitotic cells like neurons. Transient reduction of protein synthesis by protein kinase R–like endoplasmic reticulum (ER) kinase (PERK)-mediated phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) is a major proteostatic survival response during ER stress. Paradoxically, neurons are remarkably tolerant to PERK dysfunction, which suggests the existence of cell type-specific mechanisms that secure proteostatic stress resilience. We employed PERK-deficient neuron and astrocyte monocultures to investigate the mechanisms underlying neuron-specific ER stress resilience in the absence of PERK.
2022-06-13 | GSE200742 | GEO
Project description:Cellular stress response pathways often require transcription-based activation of gene expression to promote cellular adaptation. However, whether general mechanisms exist for stress-responsive gene down-regulation is less clear. A recently defined gene regulatory mechanism enables both up- and down-regulation of protein levels for distinct gene sets by the same transcription factor (TF) via coordinated induction of canonical mRNAs and long undecoded transcript isoforms (LUTIs). We analyzed deep, parallel gene expression datasets to determine whether this mechanism contributes to the conserved Hac1-driven branch of the unfolded protein response (UPRER). Indeed, we found Hac1-dependent protein down-regulation that accompanied the well-characterized up-regulation of ER-related proteins that typifies UPRER activation. Proteins down-regulated by Hac1-driven LUTIs include those with electron transport chain (ETC) function. Aerobic respiration also appears dampened during the UPRER, and abrogated ETC function improves the fitness of UPRER-activated cells, suggesting functional importance of LUTI regulation during the UPRER. We conclude that the UPRER involves large-scale proteome remodeling, mediated in part by Hac1-induced LUTIs, and that this mechanism enables coordination of up- and down-regulation of gene expression during this stress response.
2018-08-26 | GSE115366 | GEO