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Nature Reviews. Molecular Cell Biology May 2019Mitochondria are essential for the viability of eukaryotic cells as they perform crucial functions in bioenergetics, metabolism and signalling and have been associated... (Review)
Review
Mitochondria are essential for the viability of eukaryotic cells as they perform crucial functions in bioenergetics, metabolism and signalling and have been associated with numerous diseases. Recent functional and proteomic studies have revealed the remarkable complexity of mitochondrial protein organization. Protein machineries with diverse functions such as protein translocation, respiration, metabolite transport, protein quality control and the control of membrane architecture interact with each other in dynamic networks. In this Review, we discuss the emerging role of the mitochondrial protein import machinery as a key organizer of these mitochondrial protein networks. The preprotein translocases that reside on the mitochondrial membranes not only function during organelle biogenesis to deliver newly synthesized proteins to their final mitochondrial destination but also cooperate with numerous other mitochondrial protein complexes that perform a wide range of functions. Moreover, these protein networks form membrane contact sites, for example, with the endoplasmic reticulum, that are key for integration of mitochondria with cellular function, and defects in protein import can lead to diseases.
Topics: Animals; Endoplasmic Reticulum; Humans; Mitochondria; Mitochondrial Membranes; Mitochondrial Proteins; Protein Transport; Signal Transduction
PubMed: 30626975
DOI: 10.1038/s41580-018-0092-0 -
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 -
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 -
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 -
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 -
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 -
The Protein Journal Jun 2019Cells in all domains of life must translocate newly synthesized proteins both across membranes and into membranes. In eukaryotes, proteins are translocated into the... (Review)
Review
Cells in all domains of life must translocate newly synthesized proteins both across membranes and into membranes. In eukaryotes, proteins are translocated into the lumen of the ER or the ER membrane. In prokaryotes, proteins are translocated into the cytoplasmic membrane or through the membrane into the periplasm for Gram-negative bacteria or the extracellular space for Gram-positive bacteria. Much of what we know about protein translocation was learned through genetic selections and screens utilizing lacZ gene fusions in Escherichia coli. This review covers the basic principles of protein translocation and how they were discovered and developed. In particular, we discuss how lacZ gene fusions and the phenotypes conferred were exploited to identify the genes involved in protein translocation and provide insights into their mechanisms of action. These approaches, which allowed the elucidation of processes that are conserved throughout the domains of life, illustrate the power of seemingly simple experiments.
Topics: Artificial Gene Fusion; Cell Membrane; Escherichia coli; Escherichia coli Proteins; Gene Fusion; Lac Operon; Protein Transport; Recombinant Fusion Proteins; SEC Translocation Channels; beta-Galactosidase
PubMed: 30684070
DOI: 10.1007/s10930-019-09813-y -
The Biochemical Journal Feb 2022Insulin rapidly stimulates GLUT4 translocation and glucose transport in fat and muscle cells. Signals from the occupied insulin receptor are translated into downstream...
Insulin rapidly stimulates GLUT4 translocation and glucose transport in fat and muscle cells. Signals from the occupied insulin receptor are translated into downstream signalling changes in serine/threonine kinases within timescales of seconds, and this is followed by delivery and accumulation of the glucose transporter GLUT4 at the plasma membrane. Kinetic studies have led to realisation that there are distinct phases of this stimulation by insulin. There is a rapid initial burst of GLUT4 delivered to the cell surface from a subcellular reservoir compartment and this is followed by a steady-state level of continuing stimulation in which GLUT4 recycles through a large itinerary of subcellular locations. Here, we provide an overview of the phases of insulin stimulation of GLUT4 translocation and the molecules that are currently considered to activate these trafficking steps. Furthermore, we suggest how use of new experimental approaches together with phospho-proteomic data may help to further identify mechanisms for activation of these trafficking processes.
Topics: Adipocytes; Animals; Cell Membrane; Glucose; Glucose Transporter Type 4; Humans; Insulin; Models, Biological; Muscle Cells; Phosphorylation; Protein Processing, Post-Translational; Protein Transport; Signal Transduction; Subcellular Fractions
PubMed: 35147164
DOI: 10.1042/BCJ20210073 -
The Journal of Biological Chemistry Jul 2022An ever-increasing number of proteins have been shown to translocate across various membranes of bacterial as well as eukaryotic cells in their folded states as a part... (Review)
Review
An ever-increasing number of proteins have been shown to translocate across various membranes of bacterial as well as eukaryotic cells in their folded states as a part of physiological and/or pathophysiological processes. Herein, we provide an overview of the systems/processes that are established or likely to involve the membrane translocation of folded proteins, such as protein export by the twin-arginine translocation system in bacteria and chloroplasts, unconventional protein secretion and protein import into the peroxisome in eukaryotes, and the cytosolic entry of proteins (e.g., bacterial toxins) and viruses into eukaryotes. We also discuss the various mechanistic models that have previously been proposed for the membrane translocation of folded proteins including pore/channel formation, local membrane disruption, membrane thinning, and transport by membrane vesicles. Finally, we introduce a newly discovered vesicular transport mechanism, vesicle budding and collapse, and present evidence that vesicle budding and collapse may represent a unifying mechanism that drives some (and potentially all) of folded protein translocation processes.
Topics: Bacteria; Bacterial Proteins; Eukaryota; Membrane Transport Proteins; Peroxisomes; Protein Folding; Protein Sorting Signals; Protein Transport; Twin-Arginine-Translocation System
PubMed: 35671825
DOI: 10.1016/j.jbc.2022.102107