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Cell Apr 2020Many cytosolic proteins lacking a signal peptide, called leaderless cargoes, are secreted through unconventional secretion. Vesicle trafficking is a major pathway...
Many cytosolic proteins lacking a signal peptide, called leaderless cargoes, are secreted through unconventional secretion. Vesicle trafficking is a major pathway involved. It is unclear how leaderless cargoes enter into the vesicle. Here, we find a translocation pathway regulating vesicle entry and secretion of leaderless cargoes. We identify TMED10 as a protein channel for the vesicle entry and secretion of many leaderless cargoes. The interaction of TMED10 C-terminal region with a motif in the cargo accounts for the selective release of the cargoes. In an in vitro reconstitution assay, TMED10 directly mediates the membrane translocation of leaderless cargoes into the liposome, which is dependent on protein unfolding and enhanced by HSP90s. In the cell, TMED10 localizes on the endoplasmic reticulum (ER)-Golgi intermediate compartment and directs the entry of cargoes into this compartment. Furthermore, cargo induces the formation of TMED10 homo-oligomers which may act as a protein channel for cargo translocation.
Topics: Animals; Biological Transport; Cell Line; Cell Line, Tumor; Cell Membrane; Cytosol; Endoplasmic Reticulum; Golgi Apparatus; Humans; Mice; Mice, Inbred C57BL; Protein Sorting Signals; Protein Translocation Systems; Protein Transport; Proteins; Secretory Pathway; Vesicular Transport Proteins
PubMed: 32272059
DOI: 10.1016/j.cell.2020.03.031 -
Frontiers in Bioscience (Landmark... Jan 2023Fatty acids (FAs) are critical nutrients that regulate an organism's health and development in mammal. Long-chain fatty acids (LCFAs) can be divided into saturated and... (Review)
Review
Fatty acids (FAs) are critical nutrients that regulate an organism's health and development in mammal. Long-chain fatty acids (LCFAs) can be divided into saturated and unsaturated fatty acids, depending on whether the carbon chain contains at least 1 double bond. The fatty acids that are required for humans and animals are obtained primarily from dietary sources, and LCFAs are absorbed from outside of cells in mammals. LCFAs enter cells through several mechanisms, including passive diffusion and protein-mediated translocation across the plasma membrane, the latter in which FA translocase (FAT/CD36), plasma membrane FA-binding protein (FABPpm), FA transport protein (FATP), and caveolin-1 are believed to have important functions. The LCFAs that are taken up by cells bind to FA-binding proteins (FABPs) and are transported to the specific organelles, where they are activated into acyl-CoA to target specific metabolic pathways. LCFA-CoAs can be esterified to phospholipids, triacylglycerol, cholesteryl ester, and other specialized lipids. Non-esterified free fatty acids are preferentially stored as triacylglycerol molecules. The main pathway by which fatty acids are catabolized is β-oxidation, which occurs in mitochondria and peroxisomes. stearoyl-CoA desaturase (SCD)-dependent and Fatty acid desaturases (FADS)-dependent fatty acid desaturation pathways coexist in cells and provide metabolic plasticity. The process of fatty acid elongation occurs by cycling through condensation, reduction, dehydration, and reduction. Extracellular LCFA can be mediated by membrane protein G protein-coupled receptor 40 (GPR40) or G protein-coupled receptor 120 (GPR120) to activate mammalian target of rapamycin complex 1 (mTORC1) signaling, and intracellular LCFA's sensor remains to be determined. The crystal structures of a phosphatidic acid phosphatase and a membrane-bound fatty acid elongase-condensing enzyme and other LCFA-related proteins provide important insights into the mechanism of utilization, increasing our understanding of the cellular uptake, metabolism and sensing of LCFAs.
Topics: Animals; Humans; Biological Transport; Cell Membrane; Fatty Acids; Membrane Proteins; Mitochondria; Protein Transport
PubMed: 36722264
DOI: 10.31083/j.fbl2801010 -
Seminars in Cell & Developmental Biology Nov 2020In eukaryotic cells, protein sorting is a highly regulated mechanism important for many physiological events. After synthesis in the endoplasmic reticulum and... (Review)
Review
In eukaryotic cells, protein sorting is a highly regulated mechanism important for many physiological events. After synthesis in the endoplasmic reticulum and trafficking to the Golgi apparatus, proteins sort to many different cellular destinations including the endolysosomal system and the extracellular space. Secreted proteins need to be delivered directly to the cell surface. Sorting of secreted proteins from the Golgi apparatus has been a topic of interest for over thirty years, yet there is still no clear understanding of the machinery that forms the post-Golgi carriers. Most evidence points to these post-Golgi carriers being tubular pleomorphic structures that bud from the -face of the Golgi. In this review, we present the background studies and highlight the key components of this pathway, we then discuss the machinery implicated in the formation of these carriers, their translocation across the cytosol, and their fusion at the plasma membrane.
Topics: Animals; Cell Membrane; Golgi Apparatus; Humans; Lipid Metabolism; Membrane Fusion; Protein Transport; Secretory Pathway
PubMed: 32317144
DOI: 10.1016/j.semcdb.2020.04.001 -
Nature Nov 2022Multipass membrane proteins play numerous roles in biology and include receptors, transporters, ion channels and enzymes. How multipass proteins are co-translationally...
Multipass membrane proteins play numerous roles in biology and include receptors, transporters, ion channels and enzymes. How multipass proteins are co-translationally inserted and folded at the endoplasmic reticulum is not well understood. The prevailing model posits that each transmembrane domain (TMD) of a multipass protein successively passes into the lipid bilayer through a front-side lateral gate of the Sec61 protein translocation channel. The PAT complex, an intramembrane chaperone comprising Asterix and CCDC47, engages early TMDs of multipass proteins to promote their biogenesis by an unknown mechanism. Here, biochemical and structural analysis of intermediates during multipass protein biogenesis showed that the nascent chain is not engaged with Sec61, which is occluded and latched closed by CCDC47. Instead, Asterix binds to and redirects the substrate to a location behind Sec61, where the PAT complex contributes to a multipass translocon surrounding a semi-enclosed, lipid-filled cavity. Detection of multiple TMDs in this cavity after their emergence from the ribosome suggests that multipass proteins insert and fold behind Sec61. Accordingly, biogenesis of several multipass proteins was unimpeded by inhibitors of the Sec61 lateral gate. These findings elucidate the mechanism of an intramembrane chaperone and suggest a new framework for multipass membrane protein biogenesis at the endoplasmic reticulum.
Topics: Endoplasmic Reticulum; Membrane Proteins; Molecular Chaperones; Protein Transport; SEC Translocation Channels; Lipid Bilayers; Ribosomes; Carrier Proteins
PubMed: 36261528
DOI: 10.1038/s41586-022-05336-2 -
Cell Dec 2022The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of...
The TOC and TIC complexes are essential translocons that facilitate the import of the nuclear genome-encoded preproteins across the two envelope membranes of chloroplast, but their exact molecular identities and assembly remain unclear. Here, we report a cryoelectron microscopy structure of TOC-TIC supercomplex from Chlamydomonas, containing a total of 14 identified components. The preprotein-conducting pore of TOC is a hybrid β-barrel co-assembled by Toc120 and Toc75, while the potential translocation path of TIC is formed by transmembrane helices from Tic20 and YlmG, rather than a classic model of Tic110. A rigid intermembrane space (IMS) scaffold bridges two chloroplast membranes, and a large hydrophilic cleft on the IMS scaffold connects TOC and TIC, forming a pathway for preprotein translocation. Our study provides structural insights into the TOC-TIC supercomplex composition, assembly, and preprotein translocation mechanism, and lays a foundation to interpret the evolutionary conservation and diversity of this fundamental translocon machinery.
Topics: Chloroplasts; Cryoelectron Microscopy; Intracellular Membranes; Protein Transport; Chlamydomonas; Multiprotein Complexes; Algal Proteins
PubMed: 36413996
DOI: 10.1016/j.cell.2022.10.030 -
Molecular Cell Jan 2022Most mitochondrial proteins are translated in the cytosol and imported into mitochondria. Mutations in the mitochondrial protein import machinery cause human...
Most mitochondrial proteins are translated in the cytosol and imported into mitochondria. Mutations in the mitochondrial protein import machinery cause human pathologies. However, a lack of suitable tools to measure protein uptake across the mitochondrial proteome has prevented the identification of specific proteins affected by import perturbation. Here, we introduce mePROD, a pulsed-SILAC based proteomics approach that includes a booster signal to increase the sensitivity for mitochondrial proteins selectively, enabling global dynamic analysis of endogenous mitochondrial protein uptake in cells. We applied mePROD to determine protein uptake kinetics and examined how inhibitors of mitochondrial import machineries affect protein uptake. Monitoring changes in translation and uptake upon mitochondrial membrane depolarization revealed that protein uptake was extensively modulated by the import and translation machineries via activation of the integrated stress response. Strikingly, uptake changes were not uniform, with subsets of proteins being unaffected or decreased due to changes in translation or import capacity.
Topics: Carbonyl Cyanide m-Chlorophenyl Hydrazone; Electron Transport Complex I; Female; HeLa Cells; Humans; Kinetics; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Proteins; Protein Biosynthesis; Protein Transport; Proteome; Proteomics; Uncoupling Agents
PubMed: 34847359
DOI: 10.1016/j.molcel.2021.11.004 -
Microbiological Research Oct 2019T. gondii is a major opportunistic pathogen chronically infecting nearly one third of the world's population. Due to the high infection and mortality rates in... (Review)
Review
T. gondii is a major opportunistic pathogen chronically infecting nearly one third of the world's population. Due to the high infection and mortality rates in immunocompromised patients and newborns, the extent or magnitude of T. gondii pathogenesis is determined mainly by host-pathogen interactions. T. gondii utilizes specialized secretory proteins to modify host cellular factors and facilitate invasion and replication. This review provides update on the recent progress in this field of research with particular emphasis on the T. gondii secretory proteins and their role in invasion and pathogenesis.
Topics: Animals; Host-Parasite Interactions; Humans; Life Cycle Stages; Protein Transport; Protozoan Proteins; Toxoplasma; Toxoplasmosis
PubMed: 31421715
DOI: 10.1016/j.micres.2019.06.003 -
Nature Cell Biology Jun 2022Mechanical force controls fundamental cellular processes in health and disease, and increasing evidence shows that the nucleus both experiences and senses applied...
Mechanical force controls fundamental cellular processes in health and disease, and increasing evidence shows that the nucleus both experiences and senses applied forces. Such forces can lead to the nuclear translocation of proteins, but whether force controls nucleocytoplasmic transport, and how, remains unknown. Here we show that nuclear forces differentially control passive and facilitated nucleocytoplasmic transport, setting the rules for the mechanosensitivity of shuttling proteins. We demonstrate that nuclear force increases permeability across nuclear pore complexes, with a dependence on molecular weight that is stronger for passive than for facilitated diffusion. Owing to this differential effect, force leads to the translocation of cargoes into or out of the nucleus within a given range of molecular weight and affinity for nuclear transport receptors. Further, we show that the mechanosensitivity of several transcriptional regulators can be both explained by this mechanism and engineered exogenously by introducing appropriate nuclear localization signals. Our work unveils a mechanism of mechanically induced signalling, probably operating in parallel with others, with potential applicability across signalling pathways.
Topics: Active Transport, Cell Nucleus; Cell Nucleus; Nuclear Pore; Protein Transport; Receptors, Cytoplasmic and Nuclear
PubMed: 35681009
DOI: 10.1038/s41556-022-00927-7 -
Autophagy Apr 2023The endosomal system maintains cellular homeostasis by coordinating multiple vesicular trafficking events, and the retromer complex plays a critical role in endosomal...
The endosomal system maintains cellular homeostasis by coordinating multiple vesicular trafficking events, and the retromer complex plays a critical role in endosomal cargo recognition and sorting. Here, we demonstrate an essential role for the small GTPase RAB21 in regulating retromer-mediated recycling of the glucose transporter SLC2A1/GLUT1 and macroautophagy/autophagy. RAB21 depletion mis-sorts SLC2A1 to lysosomes and affects glucose uptake, thereby activating the AMPK-ULK1 pathway to increase autophagic flux. RAB21 depletion also increases lysosome function. Notably, RAB21 depletion does not overtly affect retrograde transport of IGF2R/CI-M6PR or WLS from endosomes to the trans-Golgi network. We speculate that RAB21 regulates fission of retromer-decorated endosomal tubules, as RAB21 depletion causes accumulation of the SNX27-containing retromer complex on enlarged endosomes at the perinuclear region. Functionally, RAB21 depletion sensitizes cancer cells to energy stress and inhibits tumor growth in vivo, suggesting an oncogenic role for RAB21. Overall, our study illuminates the role of RAB21 in regulating endosomal dynamics and maintaining cellular energy homeostasis and suggests RAB21 as a potential metabolic target for cancer therapy.
Topics: Vesicular Transport Proteins; Autophagy; Glucose Transporter Type 1; Protein Transport; Endosomes; Homeostasis
PubMed: 35993307
DOI: 10.1080/15548627.2022.2114271 -
Molecular Plant Aug 2021Drought is the leading environmental threat affecting crop productivity, and plants have evolved a series of mechanisms to adapt to drought stress. The FT-interacting...
Drought is the leading environmental threat affecting crop productivity, and plants have evolved a series of mechanisms to adapt to drought stress. The FT-interacting proteins (FTIPs) and phosphatidylethanolamine-binding proteins (PEBPs) play key roles in developmental processes, whereas their roles in the regulation of stress response are still largely unknown. Here, we report that OsFTIP1 negatively regulates drought response in rice. We showed that OsFTIP1 interacts with rice MOTHER OF FT AND TFL1 (OsMFT1), a PEBP that promotes rice tolerance to drought treatment. Further studies discovered that OsMFT1 interacts with two key drought-related transcription factors, OsbZIP66 and OsMYB26, regulating their binding capacity on drought-related genes and thereby enhancing drought tolerance in rice. Interestingly, we found that OsFTIP1 impedes the nucleocytoplasmic translocation of OsMFT1, implying that dynamic modulation of drought-responsive genes by the OsMFT1-OsMYB26 and OsMFT1-OsbZIP66 complexes is integral to OsFTIP1-modulated nuclear accumulation of OsMFT1. Our findings also suggest that OsMFT1 might act as a hitherto unknown nucleocytoplasmic trafficking signal that regulates drought tolerance in rice in response to environmental signals.
Topics: Adaptation, Physiological; Droughts; Gene Expression Regulation, Plant; Oryza; Plant Proteins; Plants, Genetically Modified; Protein Transport; Stress, Physiological; Transcription Factors
PubMed: 33962060
DOI: 10.1016/j.molp.2021.05.001