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Current Opinion in Structural Biology Aug 2015
Topics: Cell Membrane; Membrane Fusion; Membrane Lipids; Membrane Proteins; Periodicals as Topic
PubMed: 26489903
DOI: 10.1016/j.sbi.2015.09.006 -
Langmuir : the ACS Journal of Surfaces... Nov 2021Fusion events in living cells are intricate phenomena that require the coordinate action of multicomponent protein complexes. However, simpler synthetic tools to control...
Fusion events in living cells are intricate phenomena that require the coordinate action of multicomponent protein complexes. However, simpler synthetic tools to control membrane fusion in artificial cells are highly desirable. Native membrane fusion machinery mediates fusion, driving a delicate balance of membrane curvature and tension between two closely apposed membranes. Here, we show that silica nanoparticles (SiO NPs) at a size close to the cross-over between tension-driven and curvature-driven interaction regimes initiate efficient fusion of biomimetic model membranes. Fusion efficiency and mechanisms are studied by Förster resonance energy transfer and confocal fluorescence microscopy. SiO NPs induce a slight increase in lipid packing likely to increase the lateral tension of the membrane. We observe a connection between membrane tension and fusion efficiency. Finally, real-time confocal fluorescence microscopy reveals three distinct mechanistic pathways for membrane fusion. SiO NPs show significant potential for inclusion in the synthetic biology toolkit for membrane remodeling and fusion in artificial cells.
Topics: Biomimetics; Membrane Fusion; Membranes; Nanoparticles; Silicon Dioxide
PubMed: 34788054
DOI: 10.1021/acs.langmuir.1c02492 -
Seminars in Cell & Developmental Biology Dec 2016Influenza viral particles are enveloped by a lipid bilayer. A major step in infection is fusion of the viral and host cellular membranes, a process with large kinetic... (Review)
Review
Influenza viral particles are enveloped by a lipid bilayer. A major step in infection is fusion of the viral and host cellular membranes, a process with large kinetic barriers. Influenza membrane fusion is catalyzed by hemagglutinin (HA), a class I viral fusion protein activated by low pH. The exact nature of the HA conformational changes that deliver the energy required for fusion remains poorly understood. This review summarizes our current knowledge of HA structure and dynamics, describes recent single-particle experiments and modeling studies, and discusses their role in understanding how multiple HAs mediate fusion. These approaches provide a mechanistic picture in which HAs independently and stochastically insert into the target membrane, forming a cluster of HAs that is collectively able to overcome the barrier to membrane fusion. The new experimental and modeling approaches described in this review hold promise for a more complete understanding of other viral fusion systems and the protein systems responsible for cellular fusion.
Topics: Animals; Hemagglutinin Glycoproteins, Influenza Virus; Humans; Membrane Fusion; Models, Molecular; Orthomyxoviridae; Protein Conformation; Virus Internalization
PubMed: 27401120
DOI: 10.1016/j.semcdb.2016.07.007 -
Chemistry and Physics of Lipids Sep 2016Cholesterol modulates the bilayer structure of biological membranes in multiple ways. It changes the fluidity, thickness, compressibility, water penetration and... (Review)
Review
Cholesterol modulates the bilayer structure of biological membranes in multiple ways. It changes the fluidity, thickness, compressibility, water penetration and intrinsic curvature of lipid bilayers. In multi-component lipid mixtures, cholesterol induces phase separations, partitions selectively between different coexisting lipid phases, and causes integral membrane proteins to respond by changing conformation or redistribution in the membrane. But, which of these often overlapping properties are important for membrane fusion?-Here we review a range of recent experiments that elucidate the multiple roles that cholesterol plays in SNARE-mediated and viral envelope glycoprotein-mediated membrane fusion.
Topics: Animals; Cholesterol; Humans; Lipid Bilayers; Membrane Fusion; SNARE Proteins; Virus Internalization
PubMed: 27179407
DOI: 10.1016/j.chemphyslip.2016.05.003 -
Trends in Cell Biology Dec 2019Cell fusion is essential for the development of multicellular organisms, and plays a key role in the formation of various cell types and tissues. Recent findings have... (Review)
Review
Cell fusion is essential for the development of multicellular organisms, and plays a key role in the formation of various cell types and tissues. Recent findings have highlighted the varied protein machinery that drives plasma-membrane merger in different systems, which is characterized by diverse structural and functional elements. We highlight the discovery and activities of several key sets of fusion proteins that together offer an evolving perspective on cell membrane fusion. We also emphasize recent discoveries in vertebrate myoblast fusion in skeletal muscle, which is composed of numerous multinucleated myofibers formed by the fusion of progenitor cells during development.
Topics: Animals; Cell Fusion; Cell Membrane; Membrane Fusion; Muscle, Skeletal; Myoblasts; Myofibrils
PubMed: 31648852
DOI: 10.1016/j.tcb.2019.09.002 -
Cell Reports Mar 2023The neuropeptide VGF was recently proposed as a neurodegeneration biomarker. The Parkinson's disease-related protein leucine-rich repeat kinase 2 (LRRK2) regulates...
The neuropeptide VGF was recently proposed as a neurodegeneration biomarker. The Parkinson's disease-related protein leucine-rich repeat kinase 2 (LRRK2) regulates endolysosomal dynamics, a process that involves SNARE-mediated membrane fusion and could regulate secretion. Here we investigate potential biochemical and functional links between LRRK2 and v-SNAREs. We find that LRRK2 directly interacts with the v-SNAREs VAMP4 and VAMP7. Secretomics reveals VGF secretory defects in VAMP4 and VAMP7 knockout (KO) neuronal cells. In contrast, VAMP2 KO "regulated secretion-null" and ATG5 KO "autophagy-null" cells release more VGF. VGF is partially associated with extracellular vesicles and LAMP1+ endolysosomes. LRRK2 expression increases VGF perinuclear localization and impairs its secretion. Retention using selective hooks (RUSH) assays show that a pool of VGF traffics through VAMP4+ and VAMP7+ compartments, and LRRK2 expression delays its transport to the cell periphery. Overexpression of LRRK2 or VAMP7-longin domain impairs VGF peripheral localization in primary cultured neurons. Altogether, our results suggest that LRRK2 might regulate VGF secretion via interaction with VAMP4 and VAMP7.
Topics: Endosomes; Golgi Apparatus; Membrane Fusion; R-SNARE Proteins; SNARE Proteins; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
PubMed: 36905628
DOI: 10.1016/j.celrep.2023.112221 -
Virology Apr 2018During viral entry, enveloped viruses require the fusion of their lipid envelope with host cell membranes. For coronaviruses, this critical step is governed by the... (Review)
Review
During viral entry, enveloped viruses require the fusion of their lipid envelope with host cell membranes. For coronaviruses, this critical step is governed by the virally-encoded spike (S) protein, a class I viral fusion protein that has several unique features. Coronavirus entry is unusual in that it is often biphasic in nature, and can occur at or near the cell surface or in late endosomes. Recent advances in structural, biochemical and molecular biology of the coronavirus S protein has shed light on the intricacies of coronavirus entry, in particular the molecular triggers of coronavirus S-mediated membrane fusion. Furthermore, characterization of the coronavirus fusion peptide (FP), the segment of the fusion protein that inserts to a target lipid bilayer during membrane fusion, has revealed its particular attributes which imparts some of the unusual properties of the S protein, such as Ca-dependency. These unusual characteristics can explain at least in part the biphasic nature of coronavirus entry. In this review, using severe acute respiratory syndrome coronavirus (SARS-CoV) as model virus, we give an overview of advances in research on the coronavirus fusion peptide with an emphasis on its role and properties within the biological context of host cell entry.
Topics: Cell Membrane; Humans; Membrane Fusion; Severe acute respiratory syndrome-related coronavirus; Spike Glycoprotein, Coronavirus; Viral Envelope Proteins; Virus Internalization
PubMed: 29275820
DOI: 10.1016/j.virol.2017.12.015 -
Biomolecules Sep 2023Retinal neurons that form ribbon-style synapses operate over a wide dynamic range, continuously relaying visual information to their downstream targets. The remarkable...
Retinal neurons that form ribbon-style synapses operate over a wide dynamic range, continuously relaying visual information to their downstream targets. The remarkable signaling abilities of these neurons are supported by specialized presynaptic machinery, one component of which is syntaxin3B. Syntaxin3B is an essential t-SNARE protein of photoreceptors and bipolar cells that is required for neurotransmitter release. It has a light-regulated phosphorylation site in its N-terminal domain at T14 that has been proposed to modulate membrane fusion. However, a direct test of the latter has been lacking. Using a well-controlled in vitro fusion assay, we found that a phosphomimetic T14 syntaxin3B mutation leads to a small but significant enhancement of SNARE-mediated membrane fusion following the formation of the t-SNARE complex. While the addition of Munc18a had only a minimal effect on membrane fusion mediated by SNARE complexes containing wild-type syntaxin3B, a more significant enhancement was observed in the presence of Munc18a when the SNARE complexes contained a syntaxin3B T14 phosphomimetic mutant. Finally, we showed that the retinal-specific complexins (Cpx III and Cpx IV) inhibited membrane fusion mediated by syntaxin3B-containing SNARE complexes in a dose-dependent manner. Collectively, our results establish that membrane fusion mediated by syntaxin3B-containing SNARE complexes is regulated by the T14 residue of syntaxin3B, Munc18a, and Cpxs III and IV.
Topics: Membrane Fusion; Synapses; Synaptic Transmission; Retina; SNARE Proteins; Protein Binding
PubMed: 37892145
DOI: 10.3390/biom13101463 -
Molecular Biology of the Cell Nov 2022Membrane fusion is driven by Sec17, Sec18, and SNARE zippering. Sec17 bound to SNAREs promotes fusion through its membrane-proximal N-terminal apolar loop domain. At its...
Membrane fusion is driven by Sec17, Sec18, and SNARE zippering. Sec17 bound to SNAREs promotes fusion through its membrane-proximal N-terminal apolar loop domain. At its membrane-distal end, Sec17 serves as a high-affinity receptor for Sec18. At that distance from the fusion site, it has been unclear how Sec18 can aid Sec17 to promote fusion. We now report that Sec18, with ATPγS, lowers the Km of Sec17 for fusion. A C-terminal and membrane-distal Sec17 mutation, L291A,L292A, diminishes Sec17 affinity for Sec18. High levels of wild-type Sec17 or Sec17-L291AL292A show equivalent fusion without Sec18, but Sec18 causes far less fusion enhancement with low levels of Sec17-L291AL292A than with wild-type Sec17. Another mutant, Sec17-F21SM22S, has reduced N-loop apolarity. Only very high levels of this mutant protein support fusion, but Sec18 still lowers the apparent fusion Km for Sec17-F21SM22S. Thus Sec18 stimulates fusion through Sec17 and acts at the well-described interface between Sec18 and Sec17. ATP acts as a ligand to activate Sec18 for Sec17-dependent fusion, but ATP hydrolysis is not required. Even without SNAREs, Sec18 and Sec17 exhibit interdependent stable association with lipids, with several Sec17 bound for each Sec18 hexamer, explaining how Sec18 stabilization of surface-concentrated clusters of Sec17 lowers the Sec17 Km for assembly with SNAREs. Each of the associations, between SNARE complex, Sec18, Sec17, and lipid, helps assemble the fusion machinery.
Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Ligands; Lipids; Membrane Fusion; Mutant Proteins; SNARE Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; Vesicular Transport Proteins
PubMed: 36103252
DOI: 10.1091/mbc.E22-07-0274 -
The Journal of General Physiology Mar 2017Ca-triggered exocytosis functions broadly in the secretion of chemical signals, enabling neurons to release neurotransmitters and endocrine cells to release hormones.... (Review)
Review
Ca-triggered exocytosis functions broadly in the secretion of chemical signals, enabling neurons to release neurotransmitters and endocrine cells to release hormones. The biological demands on this process can vary enormously. Although synapses often release neurotransmitter in a small fraction of a millisecond, hormone release can be orders of magnitude slower. Vesicles usually contain multiple signaling molecules that can be released selectively and conditionally. Cells are able to control the speed, concentration profile, and content selectivity of release by tuning and tailoring exocytosis to meet different biological demands. Much of this regulation depends on the fusion pore-the aqueous pathway by which molecules leave a vesicle and move out into the surrounding extracellular space. Studies of fusion pores have illuminated how cells regulate secretion. Furthermore, the formation and growth of fusion pores serve as a readout for the progress of exocytosis, thus revealing key kinetic stages that provide clues about the underlying mechanisms. Herein, we review the structure, composition, and dynamics of fusion pores and discuss the implications for molecular mechanisms as well as for the cellular regulation of neurotransmitter and hormone release.
Topics: Animals; Calcium; Cell Membrane; Exocytosis; Membrane Fusion; Neurotransmitter Agents; Secretory Vesicles
PubMed: 28167663
DOI: 10.1085/jgp.201611724