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FEBS Letters Sep 2019Phosphatidic acid (PA) is the simplest cellular glycerophospholipid characterized by unique biophysical properties: a small headgroup; negative charge; and a... (Review)
Review
Phosphatidic acid (PA) is the simplest cellular glycerophospholipid characterized by unique biophysical properties: a small headgroup; negative charge; and a phosphomonoester group. Upon interaction with lysine or arginine, PA charge increases from -1 to -2 and this change stabilizes protein-lipid interactions. The biochemical properties of PA also allow interactions with lipids in several subcellular compartments. Based on this feature, PA is involved in the regulation and amplification of many cellular signalling pathways and functions, as well as in membrane rearrangements. Thereby, PA can influence membrane fusion and fission through four main mechanisms: it is a substrate for enzymes producing lipids (lysophosphatidic acid and diacylglycerol) that are involved in fission or fusion; it contributes to membrane rearrangements by generating negative membrane curvature; it interacts with proteins required for membrane fusion and fission; and it activates enzymes whose products are involved in membrane rearrangements. Here, we discuss the biophysical properties of PA in the context of the above four roles of PA in membrane fusion and fission.
Topics: Animals; Cell Membrane; Humans; Membrane Fusion; Phosphatidic Acids
PubMed: 31365767
DOI: 10.1002/1873-3468.13563 -
Trends in Biochemical Sciences Sep 2018A major challenge for a molecular understanding of membrane trafficking has been the elucidation of high-resolution structures of large, multisubunit tethering complexes... (Review)
Review
A major challenge for a molecular understanding of membrane trafficking has been the elucidation of high-resolution structures of large, multisubunit tethering complexes that spatially and temporally control intracellular membrane fusion. Exocyst is a large hetero-octameric protein complex proposed to tether secretory vesicles at the plasma membrane to provide quality control of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated membrane fusion. Breakthroughs in methodologies, including sample preparation, biochemical characterization, fluorescence microscopy, and single-particle cryoelectron microscopy, are providing critical insights into the structure and function of the exocyst. These studies now pose more questions than answers for understanding fundamental functional mechanisms, and they open wide the door for future studies to elucidate interactions with protein and membrane partners, potential conformational changes, and molecular insights into tethering reactions.
Topics: Animals; Exocytosis; Exosomes; Humans; Membrane Fusion; SNARE Proteins
PubMed: 30055895
DOI: 10.1016/j.tibs.2018.06.012 -
Seminars in Cell & Developmental Biology Dec 2016Poxviruses comprise a large family of enveloped DNA viruses that infect vertebrates and invertebrates. Poxviruses, unlike most DNA viruses, replicate in the cytoplasm... (Review)
Review
Poxviruses comprise a large family of enveloped DNA viruses that infect vertebrates and invertebrates. Poxviruses, unlike most DNA viruses, replicate in the cytoplasm and encode enzymes and other proteins that enable entry, gene expression, genome replication, virion assembly and resistance to host defenses. Entry of vaccinia virus, the prototype member of the family, can occur at the plasma membrane or following endocytosis. Whereas many viruses encode one or two proteins for attachment and membrane fusion, vaccinia virus encodes four proteins for attachment and eleven more for membrane fusion and core entry. The entry-fusion proteins are conserved in all poxviruses and form a complex, known as the Entry Fusion Complex (EFC), which is embedded in the membrane of the mature virion. An additional membrane that encloses the mature virion and is discarded prior to entry is present on an extracellular form of the virus. The EFC is held together by multiple interactions that depend on nine of the eleven proteins. The entry process can be divided into attachment, hemifusion and core entry. All eleven EFC proteins are required for core entry and at least eight for hemifusion. To mediate fusion the virus particle is activated by low pH, which removes one or more fusion repressors that interact with EFC components. Additional EFC-interacting fusion repressors insert into cell membranes and prevent secondary infection. The absence of detailed structural information, except for two attachment proteins and one EFC protein, is delaying efforts to determine the fusion mechanism.
Topics: Animals; Cell Fusion; Humans; Membrane Fusion; Models, Biological; Poxviridae; Viral Proteins; Virus Internalization
PubMed: 27423915
DOI: 10.1016/j.semcdb.2016.07.015 -
Traffic (Copenhagen, Denmark) Dec 2017SNAREs are the core machinery mediating membrane fusion. In this review, we provide an update on the recent progress on SNAREs regulating membrane fusion events,... (Review)
Review
SNAREs are the core machinery mediating membrane fusion. In this review, we provide an update on the recent progress on SNAREs regulating membrane fusion events, especially the more detailed fusion processes dissected by well-developed biophysical methods and in vitro single molecule analysis approaches. We also briefly summarize the relevant research from Chinese laboratories and highlight the significant contributions on our understanding of SNARE-mediated membrane trafficking from scientists in China.
Topics: Cell Membrane; Cell Movement; Humans; Membrane Fusion; Protein Transport; SNARE Proteins; Vesicular Transport Proteins
PubMed: 28857378
DOI: 10.1111/tra.12524 -
FEBS Letters May 2007Membrane fusion of enveloped viruses with cellular membranes is mediated by viral glycoproteins (GP). Interaction of GP with cellular receptors alone or coupled to... (Review)
Review
Membrane fusion of enveloped viruses with cellular membranes is mediated by viral glycoproteins (GP). Interaction of GP with cellular receptors alone or coupled to exposure to the acidic environment of endosomes induces extensive conformational changes in the fusion protein which pull two membranes into close enough proximity to trigger bilayer fusion. The refolding process provides the energy for fusion and repositions both membrane anchors, the transmembrane and the fusion peptide regions, at the same end of an elongated hairpin structure in all fusion protein structures known to date. The fusion process follows several lipidic intermediate states, which are generated by the refolding process. Although the major principles of viral fusion are understood, the structures of fusion protein intermediates and their mode of lipid bilayer interaction, the structures and functions of the membrane anchors and the number of fusion proteins required for fusion, necessitate further investigations.
Topics: Animals; Cell Membrane; Humans; Membrane Fusion; Membrane Lipids; Models, Molecular; Protein Conformation; Viral Fusion Proteins
PubMed: 17320081
DOI: 10.1016/j.febslet.2007.01.093 -
European Biophysics Journal : EBJ Mar 2021In the past decade, we developed various fluorescence-based methods for monitoring membrane fusion, membrane docking, distances between membranes, and membrane... (Review)
Review
In the past decade, we developed various fluorescence-based methods for monitoring membrane fusion, membrane docking, distances between membranes, and membrane curvature. These tools were mainly developed using liposomes as model systems, which allows for the dissection of specific interactions mediated by, for example, fusion proteins. Here, we provide an overview of these methods, including two-photon fluorescence cross-correlation spectroscopy and intramembrane Förster energy transfer, with asymmetric labelling of inner and outer membrane leaflets and the calibrated use of transmembrane energy transfer to determine membrane distances below 10 nm. We discuss their application range and their limitations using examples from our work on protein-mediated vesicle docking and fusion.
Topics: Fluorescence; Liposomes; Membrane Fusion
PubMed: 33787948
DOI: 10.1007/s00249-021-01516-6 -
Journal of Neurochemistry Jun 2016Exocytosis is the process by which stored neurotransmitters and hormones are released via the fusion of secretory vesicles with the plasma membrane. It is a dynamic,... (Review)
Review
Exocytosis is the process by which stored neurotransmitters and hormones are released via the fusion of secretory vesicles with the plasma membrane. It is a dynamic, rapid and spatially restricted process involving multiple steps including vesicle trafficking, tethering, docking, priming and fusion. For many years great steps have been undertaken in our understanding of how exocytosis occurs in different cell types, with significant focus being placed on synaptic release and neurotransmission. However, this process of exocytosis is an essential component of cell signalling throughout the body and underpins a diverse array of essential physiological pathways. Many similarities exist between different cell types with regard to key aspects of the exocytosis pathway, such as the need for Ca(2+) to trigger it or the involvement of members of the N-ethyl maleimide-sensitive fusion protein attachment protein receptor protein families. However, it is also equally clear that non-neuronal cells have acquired highly specialized mechanisms to control the release of their own unique chemical messengers. This review will focus on several important non-neuronal cell types and discuss what we know about the mechanisms they use to control exocytosis and how their specialized output is relevant to the physiological role of each individual cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. Non-neuronal cells have acquired highly specialized mechanisms to control the release of unique chemical messengers, such as polarised fusion of insulin granules in pancreatic β cells targeted towards the vasculature (top). This review discusses mechanisms used in several important non-neuronal cell types to control exocytosis, and the relevance of intermediate vesicle fusion pore states (bottom) and their specialized output to the physiological role of each cell type. These include enteroendocrine cells, pancreatic β cells, astrocytes, lactotrophs and cytotoxic T lymphocytes. This article is part of a mini review series on Chromaffin cells (ISCCB Meeting, 2015).
Topics: Animals; Cell Membrane; Endocrine System; Exocytosis; Membrane Fusion; Nerve Tissue Proteins; Neuroglia; Secretory Vesicles
PubMed: 26938142
DOI: 10.1111/jnc.13602 -
Biochemical Society Transactions Aug 2022Visualization of cellular dynamics using fluorescent light microscopy has become a reliable and indispensable source of experimental evidence for biological studies.... (Review)
Review
Visualization of cellular dynamics using fluorescent light microscopy has become a reliable and indispensable source of experimental evidence for biological studies. Over the past two decades, the development of super-resolution microscopy platforms coupled with innovations in protein and molecule labeling led to significant biological findings that were previously unobservable due to the barrier of the diffraction limit. As a result, the ability to image the dynamics of cellular processes is vastly enhanced. These imaging tools are extremely useful in cellular physiology for the study of vesicle fusion and endocytosis. In this review, we will explore the power of stimulated emission depletion (STED) and confocal microscopy in combination with various labeling techniques in real-time observation of the membrane transformation of fusion and endocytosis, as well as their underlying mechanisms. We will review how STED and confocal imaging are used to reveal fusion and endocytic membrane transformation processes in live cells, including hemi-fusion; hemi-fission; hemi-to-full fusion; fusion pore opening, expansion, constriction and closure; shrinking or enlargement of the Ω-shape membrane structure after vesicle fusion; sequential compound fusion; and the sequential endocytic membrane transformation from flat- to O-shape via the intermediate Λ- and Ω-shape transition. We will also discuss how the recent development of imaging techniques would impact future studies in the field.
Topics: Cell Membrane; Endocytosis; Exocytosis; Membrane Fusion; Microscopy, Confocal; Secretory Vesicles
PubMed: 35960003
DOI: 10.1042/BST20210263 -
Biochimica Et Biophysica Acta Aug 2003Mitochondrial fusion has been observed in a great variety of organisms from yeast to man. It serves to mix and unify the mitochondrial compartment and plays roles in... (Review)
Review
Mitochondrial fusion has been observed in a great variety of organisms from yeast to man. It serves to mix and unify the mitochondrial compartment and plays roles in cellular aging, cell development, energy dissipation and mitochondrial DNA inheritance. Large GTPases in the mitochondrial outer membrane, termed Fzo or mitofusins, have been identified as key components of the mitochondrial fusion machinery in yeast, flies and mammalian cells. Recent studies in yeast suggest an involvement of a dynamin-related protein in the intermembrane space. Additional components have been identified by genetic screens. These findings suggest a unique and evolutionarily conserved mechanism for mitochondrial membrane fusion.
Topics: Animals; Drosophila Proteins; Fungi; GTP Phosphohydrolases; Humans; Membrane Fusion; Membrane Proteins; Mitochondria
PubMed: 12914960
DOI: 10.1016/s0167-4889(03)00091-0 -
Nature Mar 2022Membrane fusion triggered by Ca is orchestrated by a conserved set of proteins to mediate synaptic neurotransmitter release, mucin secretion and other regulated exocytic...
Membrane fusion triggered by Ca is orchestrated by a conserved set of proteins to mediate synaptic neurotransmitter release, mucin secretion and other regulated exocytic processes. For neurotransmitter release, the Ca sensitivity is introduced by interactions between the Ca sensor synaptotagmin and the SNARE complex, and sequence conservation and functional studies suggest that this mechanism is also conserved for mucin secretion. Disruption of Ca-triggered membrane fusion by a pharmacological agent would have therapeutic value for mucus hypersecretion as it is the major cause of airway obstruction in the pathophysiology of respiratory viral infection, asthma, chronic obstructive pulmonary disease and cystic fibrosis. Here we designed a hydrocarbon-stapled peptide that specifically disrupts Ca-triggered membrane fusion by interfering with the so-called primary interface between the neuronal SNARE complex and the Ca-binding C2B domain of synaptotagmin-1. In reconstituted systems with these neuronal synaptic proteins or with their airway homologues syntaxin-3, SNAP-23, VAMP8, synaptotagmin-2, along with Munc13-2 and Munc18-2, the stapled peptide strongly suppressed Ca-triggered fusion at physiological Ca concentrations. Conjugation of cell-penetrating peptides to the stapled peptide resulted in efficient delivery into cultured human airway epithelial cells and mouse airway epithelium, where it markedly and specifically reduced stimulated mucin secretion in both systems, and substantially attenuated mucus occlusion of mouse airways. Taken together, peptides that disrupt Ca-triggered membrane fusion may enable the therapeutic modulation of mucin secretory pathways.
Topics: Animals; Calcium; Hydrocarbons; Membrane Fusion; Mice; Mucins; Neurotransmitter Agents; Peptides; Respiratory Mucosa; SNARE Proteins
PubMed: 35322233
DOI: 10.1038/s41586-022-04543-1