Virus entry by endocytosis.
TL;DR: This review focuses on the cell biology of virus entry and the different strategies and endocytic mechanisms used by animal viruses.
Abstract: Although viruses are simple in structure and composition, their interactions with host cells are complex. Merely to gain entry, animal viruses make use of a repertoire of cellular processes that involve hundreds of cellular proteins. Although some viruses have the capacity to penetrate into the cytosol directly through the plasma membrane, most depend on endocytic uptake, vesicular transport through the cytoplasm, and delivery to endosomes and other intracellular organelles. The internalization may involve clathrin-mediated endocytosis (CME), macropinocytosis, caveolar/lipid raft-mediated endocytosis, or a variety of other still poorly characterized mechanisms. This review focuses on the cell biology of virus entry and the different strategies and endocytic mechanisms used by animal viruses.
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TL;DR: The basic concept of the nanoparticle corona is reviewed and its structure and composition is highlighted, and how the properties of the corona may be linked to its biological impacts are highlighted.
Abstract: The search for understanding the interactions of nanosized materials with living organisms is leading to the rapid development of key applications, including improved drug delivery by targeting nanoparticles, and resolution of the potential threat of nanotechnological devices to organisms and the environment. Unless they are specifically designed to avoid it, nanoparticles in contact with biological fluids are rapidly covered by a selected group of biomolecules to form a corona that interacts with biological systems. Here we review the basic concept of the nanoparticle corona and its structure and composition, and highlight how the properties of the corona may be linked to its biological impacts. We conclude with a critical assessment of the key problems that need to be resolved in the near future.
2,245 citations
TL;DR: The maturation programme entails a dramatic transformation of these dynamic organelles disconnecting them functionally and spatially from early endosomes and preparing them for their unidirectional role as a feeder pathway to lysosomes.
Abstract: Being deeply connected to signalling, cell dynamics, growth, regulation, and defence, endocytic processes are linked to almost all aspects of cell life and disease. In this review, we focus on endosomes in the classical endocytic pathway, and on the programme of changes that lead to the formation and maturation of late endosomes/multivesicular bodies. The maturation programme entails a dramatic transformation of these dynamic organelles disconnecting them functionally and spatially from early endosomes and preparing them for their unidirectional role as a feeder pathway to lysosomes.
1,859 citations
Cites background from "Virus entry by endocytosis."
...This is most clearly illustrated by viruses and bacterial toxins that have a relative sharp pH threshold adjusted so that they are specifically activated when they arrive in EEs, in LEs, or in lysosomes (Mercer et al, 2010)....
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...The reason for concentrating again on this topic is our interest in host cell entry of animal viruses, the majority of which enter cells by endocytosis and exploit endosomes and the endocytic pathways for penetration into the cytosol (Marsh and Helenius, 1989; Mercer et al, 2010)....
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TL;DR: How the field has matured and an evolving model in which membranes are occupied by fluctuating nanoscale assemblies of sphingolipids, cholesterol and proteins that can be stabilized into platforms that are important in signalling, viral infection and membrane trafficking are presented.
Abstract: Ten years ago, we wrote a Review on lipid rafts and signalling in the launch issue of Nature Reviews Molecular Cell Biology. At the time, this field was suffering from ambiguous methodology and imprecise nomenclature. Now, new techniques are deepening our insight into the dynamics of membrane organization. Here, we discuss how the field has matured and present an evolving model in which membranes are occupied by fluctuating nanoscale assemblies of sphingolipids, cholesterol and proteins that can be stabilized into platforms that are important in signalling, viral infection and membrane trafficking.
1,151 citations
Cites background from "Virus entry by endocytosis."
...Toxins and viruses have proven to be important tools for the study of endocytosis as they can be taken up by various internalization mechanism...
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TL;DR: Studies in recent years have provided several important insights into how endocytic vesicles are built, starting from initiation, cargo loading and the mechanisms governing membrane bending to membrane scission and the release of the vesicle into the cytoplasm.
Abstract: Clathrin-mediated endocytosis is a key process in vesicular trafficking that transports a wide range of cargo molecules from the cell surface to the interior. Clathrin-mediated endocytosis was first described over 5 decades ago. Since its discovery, over 50 proteins have been shown to be part of the molecular machinery that generates the clathrin-coated endocytic vesicles. These proteins and the different steps of the endocytic process that they mediate have been studied in detail. However, we still lack a good understanding of how all these different components work together in a highly coordinated manner to drive vesicle formation. Nevertheless, studies in recent years have provided several important insights into how endocytic vesicles are built, starting from initiation, cargo loading and the mechanisms governing membrane bending to membrane scission and the release of the vesicle into the cytoplasm.
956 citations
TL;DR: Understanding of the mechanisms by which dynamin acts, its essential roles in cell physiology and the specific function of different dynamin isoforms are improved, highlighting specific contributions of this GTPase to the physiology of different tissues.
Abstract: Dynamin, the founding member of a family of dynamin-like proteins (DLPs) implicated in membrane remodelling, has a critical role in endocytic membrane fission events. The use of complementary approaches, including live-cell imaging, cell-free studies, X-ray crystallography and genetic studies in mice, has greatly advanced our understanding of the mechanisms by which dynamin acts, its essential roles in cell physiology and the specific function of different dynamin isoforms. In addition, several connections between dynamin and human disease have also emerged, highlighting specific contributions of this GTPase to the physiology of different tissues.
829 citations
Cites background from "Virus entry by endocytosis."
...To support these various functions, multiple molecularly and morphologically distinct forms of endocytosis, both constitutive and regulated, operate in all cell...
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References
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TL;DR: ‘Endocytosis’ encompasses several diverse mechanisms by which cells internalize macromolecules and particles into transport vesicles derived from the plasma membrane and must be viewed in a broader context than simple vesicular trafficking.
Abstract: The plasma membrane is the interface between cells and their harsh environment. Uptake of nutrients and all communication among cells and between cells and their environment occurs through this interface. 'Endocytosis' encompasses several diverse mechanisms by which cells internalize macromolecules and particles into transport vesicles derived from the plasma membrane. It controls entry into the cell and has a crucial role in development, the immune response, neurotransmission, intercellular communication, signal transduction, and cellular and organismal homeostasis. As the complexity of molecular interactions governing endocytosis are revealed, it has become increasingly clear that it is tightly coordinated and coupled with overall cell physiology and thus, must be viewed in a broader context than simple vesicular trafficking.
3,709 citations
"Virus entry by endocytosis." refers background in this paper
...The molecular information about the various steps in clathrin coat assemblies, induction of membrane curvature, cargo recruitment, vesicle fission, and coat disassembly is extensive, and there are several recent reviews (21, 24, 148)....
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TL;DR: Cellular organelles in the exocytic and endocytic pathways have a distinctive spatial distribution and communicate through an elaborate system of vesiculo-tubular transport.
Abstract: Cellular organelles in the exocytic and endocytic pathways have a distinctive spatial distribution and communicate through an elaborate system of vesiculo-tubular transport. Rab proteins and their effectors coordinate consecutive stages of transport, such as vesicle formation, vesicle and organelle motility, and tethering of vesicles to their target compartment. These molecules are highly compartmentalized in organelle membranes, making them excellent candidates for determining transport specificity and organelle identity.
3,373 citations
"Virus entry by endocytosis." refers background in this paper
...The membrane is composed of a patchwork of functionally different domains (20, 23, 44)....
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TL;DR: What is known about mammalian endocytic mechanisms is reviewed, with focus on the cellular proteins that control these events, and the functional relevance of distinctendocytic pathways is discussed.
Abstract: Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Here, we review what is known about mammalian endocytic mechanisms, with focus on the cellular proteins that control these events. We discuss the well-studied clathrin-mediated endocytic mechanisms and dissect endocytic pathways that proceed independently of clathrin. These clathrin-independent pathways include the CLIC/GEEC endocytic pathway, arf6-dependent endocytosis, flotillin-dependent endocytosis, macropinocytosis, circular doral ruffles, phagocytosis, and trans-endocytosis. We also critically review the role of caveolae and caveolin1 in endocytosis. We highlight the roles of lipids, membrane curvature-modulating proteins, small G proteins, actin, and dynamin in endocytic pathways. We discuss the functional relevance of distinct endocytic pathways and emphasize the importance of studying these pathways to understand human disease processes.
2,685 citations
"Virus entry by endocytosis." refers background in this paper
...The molecular information about the various steps in clathrin coat assemblies, induction of membrane curvature, cargo recruitment, vesicle fission, and coat disassembly is extensive, and there are several recent reviews (21, 24, 148)....
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TL;DR: In this article, the vitronectin-binding integrins α v β 3 and β 5 promote viral infection in a novel way since antibodies against these receptors or soluble penton base block virus internalization without affecting attachment.
2,261 citations
TL;DR: The results provide evidence for the existence of an active proton accumulation mechanism in the lysosomal membrane and support the theory of lysOSomal accumulation of weak bases by proton trapping.
Abstract: A quantitative method is described for the measurement of intralysosomal pH in living cells. Fluorescein isothiocyanate-labeled dextran (FD) is endocytized and accumulates in lysosomes where it remains without apparent degradation. The fluorescence spectrum of this compound changes with pH in the range 4-7 and is not seriously affected by FD concentration, ionic strength, or protein concentration. Living cells on coverslips are mounted in a spectrofluorometer cell and can be perfused with various media. The normal pH inside macrophage lysosomes seems to be 4.7-4.8, although it can drop transiently as low as 4.5. Exposure of the cells to various weak bases and to acidic potassium ionophores causes the pH to increase. The changes in pH are much more rapid than is the intralysosomal accumulation of the weak bases. Inhibitors of glycolysis (2-deoxyglucose) and of oxidative phosphorylation (cyanide or azide) added together, but not separately, cause the intralysosomal pH to increase. These results provide evidence for the existence of an active proton accumulation mechanism in the lysosomal membrane and support the theory of lysosomal accumulation of weak bases by proton trapping.
2,045 citations
"Virus entry by endocytosis." refers background in this paper
...Weak bases raise the pH almost instantly after addition, which makes them useful agents for determining the time course of the acid activation step (80)....
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