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Trends in Cell Biology Mar 2017Secretory proteins are conventionally transported through the endoplasmic reticulum to the Golgi and then to the plasma membrane where they are released into the... (Review)
Review
Secretory proteins are conventionally transported through the endoplasmic reticulum to the Golgi and then to the plasma membrane where they are released into the extracellular space. However, numerous substrates also reach these destinations using unconventional pathways. Unconventional protein secretion (UPS) is complex and comprises cargos without a signal peptide or a transmembrane domain that can translocate across the plasma membrane, and cargos that reach the plasma membrane by bypassing the Golgi despite entering the endoplasmic reticulum (ER). With a few exceptions, unconventional secretion is largely triggered by stress. Here I review new results and concepts that are beginning to define these pathways.
Topics: Animals; Cell Membrane; Endoplasmic Reticulum Stress; Humans; Protein Transport; Proteins; Secretory Pathway
PubMed: 27989656
DOI: 10.1016/j.tcb.2016.11.007 -
Proceedings of the National Academy of... May 2023Integral membrane protein structure determination traditionally requires extraction from cell membranes using detergents or polymers. Here, we describe the isolation and...
Integral membrane protein structure determination traditionally requires extraction from cell membranes using detergents or polymers. Here, we describe the isolation and structure determination of proteins in membrane vesicles derived directly from cells. Structures of the ion channel Slo1 from total cell membranes and from cell plasma membranes were determined at 3.8 Å and 2.7 Å resolution, respectively. The plasma membrane environment stabilizes Slo1, revealing an alteration of global helical packing, polar lipid, and cholesterol interactions that stabilize previously unresolved regions of the channel and an additional ion binding site in the Ca regulatory domain. The two methods presented enable structural analysis of both internal and plasma membrane proteins without disrupting weakly interacting proteins, lipids, and cofactors that are essential to biological function.
Topics: Membrane Proteins; Cell Membrane; Ion Channels; Binding Sites
PubMed: 37098056
DOI: 10.1073/pnas.2302325120 -
International Journal of Molecular... May 2019Biological membranes are key elements for the maintenance of cell architecture and physiology. Beyond a pure barrier separating the inner space of the cell from the... (Review)
Review
Biological membranes are key elements for the maintenance of cell architecture and physiology. Beyond a pure barrier separating the inner space of the cell from the outer, the plasma membrane is a scaffold and player in cell-to-cell communication and the initiation of intracellular signals among other functions. Critical to this function is the plasma membrane compartmentalization in lipid microdomains that control the localization and productive interactions of proteins involved in cell signal propagation. In addition, cells are divided into compartments limited by other membranes whose integrity and homeostasis are finely controlled, and which determine the identity and function of the different organelles. Here, we review current knowledge on membrane lipid composition in the plasma membrane and endomembrane compartments, emphasizing its role in sustaining organelle structure and function. The correct composition and structure of cell membranes define key pathophysiological aspects of cells. Therefore, we explore the therapeutic potential of manipulating membrane lipid composition with approaches like membrane lipid therapy, aiming to normalize cell functions through the modification of membrane lipid bilayers.
Topics: Animals; Cell Compartmentation; Cell Membrane; Fatty Acids, Unsaturated; Humans; Membrane Lipids; Metabolic Diseases; Neoplasms; Neurodegenerative Diseases
PubMed: 31052427
DOI: 10.3390/ijms20092167 -
Nature Reviews. Molecular Cell Biology Nov 2018Newly endocytosed integral cell surface proteins are typically either directed for degradation or subjected to recycling back to the plasma membrane. The sorting of... (Review)
Review
Newly endocytosed integral cell surface proteins are typically either directed for degradation or subjected to recycling back to the plasma membrane. The sorting of integral cell surface proteins, including signalling receptors, nutrient transporters, ion channels, adhesion molecules and polarity markers, within the endolysosomal network for recycling is increasingly recognized as an essential feature in regulating the complexities of physiology at the cell, tissue and organism levels. Historically, endocytic recycling has been regarded as a relatively passive process, where the majority of internalized integral proteins are recycled via a nonspecific sequence-independent 'bulk membrane flow' pathway. Recent work has increasingly challenged this view. The discovery of sequence-specific sorting motifs and the identification of cargo adaptors and associated coat complexes have begun to uncover the highly orchestrated nature of endosomal cargo recycling, thereby providing new insight into the function and (patho)physiology of this process.
Topics: Animals; Cell Membrane; Endocytosis; Endosomes; Humans; Membrane Proteins; Protein Transport
PubMed: 30194414
DOI: 10.1038/s41580-018-0053-7 -
International Journal of Molecular... Apr 2020Beyond the consolidated role in degrading and recycling cellular waste, the autophagic- and endo-lysosomal systems play a crucial role in extracellular release pathways.... (Review)
Review
Beyond the consolidated role in degrading and recycling cellular waste, the autophagic- and endo-lysosomal systems play a crucial role in extracellular release pathways. Lysosomal exocytosis is a process leading to the secretion of lysosomal content upon lysosome fusion with plasma membrane and is an important mechanism of cellular clearance, necessary to maintain cell fitness. Exosomes are a class of extracellular vesicles originating from the inward budding of the membrane of late endosomes, which may not fuse with lysosomes but be released extracellularly upon exocytosis. In addition to garbage disposal tools, they are now considered a cell-to-cell communication mechanism. Autophagy is a cellular process leading to sequestration of cytosolic cargoes for their degradation within lysosomes. However, the autophagic machinery is also involved in unconventional protein secretion and autophagy-dependent secretion, which are fundamental mechanisms for toxic protein disposal, immune signalling and pathogen surveillance. These cellular processes underline the crosstalk between the autophagic and the endosomal system and indicate an intersection between degradative and secretory functions. Further, they suggest that the molecular mechanisms underlying fusion, either with lysosomes or plasma membrane, are key determinants to maintain cell homeostasis upon stressing stimuli. When they fail, the accumulation of undigested substrates leads to pathological consequences, as indicated by the involvement of autophagic and lysosomal alteration in human diseases, namely lysosomal storage disorders, age-related neurodegenerative diseases and cancer. In this paper, we reviewed the current knowledge on the functional role of extracellular release pathways involving lysosomes and the autophagic- and endo-lysosomal systems, evaluating their implication in health and disease.
Topics: Animals; Autophagy; Cell Membrane; Endosomes; Exocytosis; Exosomes; Extracellular Vesicles; Humans; Lysosomes
PubMed: 32276321
DOI: 10.3390/ijms21072576 -
Current Biology : CB Apr 2018Tissue wound repair has been studied extensively. It involves the coordinated activation of several intracellular and intercellular pathways, as well as remodeling from... (Review)
Review
Tissue wound repair has been studied extensively. It involves the coordinated activation of several intracellular and intercellular pathways, as well as remodeling from the sequential recruitment of different cell types to the wound site. There is, however, an equally important process that happens at the single cell level, when the integrity of the plasma membrane is compromised. Individual eukaryotic cells can rapidly repair their plasma membrane after injury, through a process that restores internal homeostasis and prevents cell death. Despite its importance, investigations of this fascinating mechanism have been limited. Only recently have we begun to understand that plasma-membrane repair resembles tissue healing, in the sense that it also involves sequential, highly localized remodeling steps that ultimately eliminate all traces of the injury.
Topics: Animals; Calcium; Calcium Channels; Cell Membrane; Exocytosis; Homeostasis; Humans; Wound Healing
PubMed: 29689221
DOI: 10.1016/j.cub.2017.12.034 -
Current Biology : CB Apr 2018The plasma membrane is a ∼4 nm thick phospholipid bilayer that defines the boundary of a cell, segregating internal content from the external environment. Its... (Review)
Review
The plasma membrane is a ∼4 nm thick phospholipid bilayer that defines the boundary of a cell, segregating internal content from the external environment. Its hydrophobic interior presents a barrier to the exchange of ions and polar solutes between the inside and outside of the cell, as well as to the spontaneous reorientation of lipids between the two leaflets of the bilayer. Specific transport systems, e.g. ion channels and lipid flippases, are needed to enable the passage of these molecules across the plasma membrane at physiologically relevant rates. Although the influential fluid mosaic membrane model of 1972 depicted the membrane as an archipelago of protein islands within a uniform sea of lipids, its micrometer-scale lateral heterogeneity was recognized relatively quickly, evolving into the current picture of structural granularity at the nanoscale.
Topics: Biological Transport; Cell Membrane; Hydrodynamics; Lipid Bilayers; Lipid Metabolism; Lipids; Membrane Microdomains; Membrane Proteins
PubMed: 29689220
DOI: 10.1016/j.cub.2018.01.007 -
Cell Calcium Jun 2023Regulated exocytosis, a universal process of eukaryotic cells, involves the merging between the vesicle membrane and the plasma membrane, plays a key role in...
Regulated exocytosis, a universal process of eukaryotic cells, involves the merging between the vesicle membrane and the plasma membrane, plays a key role in cell-to-cell communication, particularly in the release of hormones and neurotransmitters. There are a number of barriers a vesicle needs to pass to discharge vesicle content to the extracellular space. At the pre-fusion site vesicles need to be transported to the sites on the plasma membrane where the merger may begin. Classically cytoskeleton was considered an important barrier for vesicle translocation and was thought to be disintegrated to allow vesicle access to the plasma membrane [1]. However, it was considered later that cytoskeletal elements may also play a role at the post-fusion stage, promoting the vesicle merger with the plasma membrane and fusion pore expansion [4,22,23]. In this Special Issue of Cell Calcium entitled "Regulated Exocytosis", the authors address outstanding issues related to vesicle chemical messenger release by regulated exocytosis, including that related to the question whether vesicle content discharge is complete or only partial upon the merging of the vesicle membrane with the plasma membrane triggered by Ca. Among processes that limit vesicle discharge at the post-fusion stage is the accumulation of cholesterol in some vesicles [19], a process that has recently been associated with cell aging [20].
Topics: Membrane Fusion; Secretory Vesicles; Cell Membrane; Hormones; Exocytosis
PubMed: 37099857
DOI: 10.1016/j.ceca.2023.102737 -
Methods in Molecular Biology (Clifton,... 2019Palmitoylation or S-acylation is the posttranslational attachment of fatty acids to cysteine residues and is common among integral and peripheral membrane proteins....
Palmitoylation or S-acylation is the posttranslational attachment of fatty acids to cysteine residues and is common among integral and peripheral membrane proteins. Palmitoylated proteins have been found in every eukaryotic cell type examined (yeast, insect, and vertebrate cells), as well as in viruses grown in these cells. The exact functions of protein palmitoylation are not well understood. Intrinsically hydrophilic proteins, especially signaling molecules, are anchored by long-chain fatty acids to the cytoplasmic face of the plasma membrane. Palmitoylation may also promote targeting to membrane subdomains enriched in glycosphingolipids and cholesterol or affect protein-protein interactions.This chapter describes (1) a standard protocol for metabolic labeling of palmitoylated proteins and also the procedures to prove a covalent and ester-type linkage of the fatty acids, (2) a simple method to analyze the fatty acid content of S-acylated proteins, (3) two methods to analyze dynamic palmitoylation for a given protein, and (4) protocols to study cell-free palmitoylation of proteins.
Topics: Acylation; Amino Acid Sequence; Cell Membrane; Fatty Acids; Lipoylation; Protein Binding; Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Staining and Labeling
PubMed: 31256385
DOI: 10.1007/978-1-4939-9055-9_17 -
FEBS Letters Nov 2020Plasma membrane carries out multiple physiological functions that require its dynamic and tightly regulated organization into specialized domains of different size,... (Review)
Review
Plasma membrane carries out multiple physiological functions that require its dynamic and tightly regulated organization into specialized domains of different size, stability, and lipid/protein composition. Sphingolipids are a group of lipids in which the plasma membrane is particularly enriched, thus being crucial for its structure and function. A specific type of sphingolipid-enriched plasma membrane domains, where ergosterol is depleted and lipids are tightly packed in a rigid gel phase, has recently been found in several fungal species, including yeasts and moulds. After presenting the main biophysical features of gel domains and the experimental method for their detection in the fungal plasma membrane, we review these sphingolipid-enriched gel domains and illustrate their importance to both unicellular and multicellular fungi. First, the biophysical properties of the fungal sphingolipid-enriched domains will be analysed taking into consideration the plasma membrane sphingolipidome. Next, their possible biological roles will be summarized, including their relations with plasma membrane compartments and involvement in stress responses. Moreover, since the plasma membrane is a target for several antifungal compounds, a biophysical connection between sphingolipid-enriched domains and antifungal action will be explored.
Topics: Carbohydrate Sequence; Cell Membrane; Fungi; Sphingolipids
PubMed: 33141925
DOI: 10.1002/1873-3468.13986