scholarly journals Transport Vesicle

2020 ◽  
Author(s):  
Keyword(s):  
Transport Vesicle

scholarly journals Insights on autophagosome–lysosome tethering from structural and biochemical characterization of human autophagy factor EPG5

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Sung-Eun Nam ◽  
Yiu Wing Sunny Cheung ◽  
Thanh Ngoc Nguyen ◽  
Michael Gong ◽  
Samuel Chan ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Late Endosome ◽  
Multisystem Disorder ◽  
Cytoplasmic Material ◽  
Disease Mutations ◽  
Evolutionarily Conserved ◽  
Overall Stability ◽  
Transport Vesicle ◽  
Molecular Effects

AbstractPivotal to the maintenance of cellular homeostasis, macroautophagy (hereafter autophagy) is an evolutionarily conserved degradation system that involves sequestration of cytoplasmic material into the double-membrane autophagosome and targeting of this transport vesicle to the lysosome/late endosome for degradation. EPG5 is a large-sized metazoan protein proposed to serve as a tethering factor to enforce autophagosome–lysosome/late endosome fusion specificity, and its deficiency causes a severe multisystem disorder known as Vici syndrome. Here, we show that human EPG5 (hEPG5) adopts an extended “shepherd’s staff” architecture. We find that hEPG5 binds preferentially to members of the GABARAP subfamily of human ATG8 proteins critical to autophagosome–lysosome fusion. The hEPG5–GABARAPs interaction, which is mediated by tandem LIR motifs that exhibit differential affinities, is required for hEPG5 recruitment to mitochondria during PINK1/Parkin-dependent mitophagy. Lastly, we find that the Vici syndrome mutation Gln336Arg does not affect the hEPG5’s overall stability nor its ability to engage in interaction with the GABARAPs. Collectively, results from our studies reveal new insights into how hEPG5 recognizes mature autophagosome and establish a platform for examining the molecular effects of Vici syndrome disease mutations on hEPG5.

scholarly journals Coupled myosin VI motors facilitate unidirectional movement on an F-actin network

2009 ◽  
Vol 187 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Sivaraj Sivaramakrishnan ◽  
James A. Spudich
Keyword(s):  
Single Molecule ◽  
Membrane Trafficking ◽  
Cell Periphery ◽  
Myosin Vi ◽  
Actin Network ◽  
Cortical Actin ◽  
Actin Cortex ◽  
Unidirectional Movement ◽  
Transport Vesicle ◽  
Pointed End

Unconventional myosins interact with the dense cortical actin network during processes such as membrane trafficking, cell migration, and mechanotransduction. Our understanding of unconventional myosin function is derived largely from assays that examine the interaction of a single myosin with a single actin filament. In this study, we have developed a model system to study the interaction between multiple tethered unconventional myosins and a model F-actin cortex, namely the lamellipodium of a migrating fish epidermal keratocyte. Using myosin VI, which moves toward the pointed end of actin filaments, we directly determine the polarity of the extracted keratocyte lamellipodium from the cell periphery to the cell nucleus. We use a combination of experimentation and simulation to demonstrate that multiple myosin VI molecules can coordinate to efficiently transport vesicle-size cargo over 10 µm of the dense interlaced actin network. Furthermore, several molecules of monomeric myosin VI, which are nonprocessive in single molecule assays, can coordinate to transport cargo with similar speeds as dimers.

scholarly journals Human Papillomavirus 16 Capsids Mediate Nuclear Entry during Infection

2019 ◽  
Vol 93 (15) ◽  
Author(s):  
Patricia M. Day ◽  
Andrea S. Weisberg ◽  
Cynthia D. Thompson ◽  
Michelle M. Hughes ◽  
Yuk Ying Pang ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Viral Entry ◽  
Large Family ◽  
Viral Capsid ◽  
Mitotic Chromosomes ◽  
Nuclear Entry ◽  
Human Papillomavirus 16 ◽  
Transport Vesicle ◽  
Causative Agents

ABSTRACTInfectious human papillomavirus 16 (HPV16) L1/L2 pseudovirions were found to remain largely intact during vesicular transport to the nucleus. By electron microscopy, capsids with a diameter of 50 nm were clearly visible within small vesicles attached to mitotic chromosomes and to a lesser extent within interphase nuclei, implying nuclear disassembly. By confocal analysis, it was determined that nuclear entry of assembled L1 is dependent upon the presence of the minor capsid protein, L2, but independent of encapsidated DNA. We also demonstrate that L1 nuclear localization and mitotic chromosome association can occurin vivoin the murine cervicovaginal challenge model of HPV16 infection. These findings challenge the prevailing concepts of PV uncoating and disassembly. More generally, they document that a largely intact viral capsid can enter the nucleus within a transport vesicle, establishing a novel mechanism by which a virus accesses the nuclear cellular machinery.IMPORTANCEPapillomaviruses (PVs) comprise a large family of nonenveloped DNA viruses that include HPV16, among other oncogenic types, the causative agents of cervical cancer. Delivery of the viral DNA into the host cell nucleus is necessary for establishment of infection. This was thought to occur via a subviral complex following uncoating of the larger viral capsid. In this study, we demonstrate that little disassembly of the PV capsid occurs prior to nuclear delivery. These surprising data reveal a previously unrecognized viral strategy to access the nuclear replication machinery. Understanding viral entry mechanisms not only increases our appreciation of basic cell biological pathways but also may lead to more effective antiviral interventions.

Identification of a Cellubrevin/Vesicle Associated Membrane Protein 3 Homologue in Human Platelets

Blood ◽  
1999 ◽  
Vol 93 (2) ◽  
pp. 571-579 ◽  
Author(s):  
Audrey M. Bernstein ◽  
Sidney W. Whiteheart
Keyword(s):  
Membrane Proteins ◽  
Complex Formation ◽  
Membrane Protein ◽  
Membrane Trafficking ◽  
Human Platelets ◽  
Degenerate Primers ◽  
Hek 293 ◽  
Transport Vesicle ◽  
Exocytic Pathway ◽  
Conserved Core

Abstract Several studies suggest membrane trafficking events are mediated by integral, membrane proteins from both transport-vesicle and target membranes, called v- and t-SNAREs (SNAp REceptors), respectively. Previous experiments using antibodies to synaptobrevin/vesicle associated membrane protein (VAMP) 1, 2, or rat cellubrevin failed to detect these v-SNAREs in human platelets, although membrane proteins from these cells could support 20S complex formation. To identify v-SNAREs in platelets, we used a polymerase chain reaction (PCR) approach with degenerate primers to amplify potential VAMP-like v-SNAREs. A cDNA encoding a novel v-SNARE was isolated from a human megakaryocyte cDNA library. Termed human cellubrevin (Hceb), this protein has greater than 93% identity with human VAMP 1, 2, and rat cellubrevin over the conserved core region, but has a unique N–terminal domain. Northern blot analysis showed that the 2.5-kB mRNA encoding Hceb is expressed in every human tissue tested. Hceb from detergent-solubilized platelet membranes, participated in -SNAP–dependent 20S complex formation and adenosine triphosphate (ATP)-dependent disassembly, showing that Hceb can act as a v-SNARE in platelets. Immunofluorescence microscopy, using an anti-Hceb antibody showed a punctate, intracellular staining pattern in platelets, megakaryocytes, and HEK-293 cells. This same pattern was observed in surface-activated platelets even though all dense core and most -granule contents had been released. These data suggest that Hceb may reside on a platelet organelle that is not primarily involved in the exocytic pathway.

Protein complexes in transport vesicle targeting

2000 ◽  
Vol 10 (6) ◽  
pp. 251-255 ◽  
Author(s):  
Wei Guo ◽  
Michael Sacher ◽  
Jemima Barrowman ◽  
Susan Ferro-Novick ◽  
Peter Novick
Keyword(s):  
Protein Complexes ◽  
Transport Vesicle

The Small GTPase Superfamily in Plants: A Conserved Regulatory Module with Novel Functions

2020 ◽  
Vol 71 (1) ◽  
pp. 247-272
Author(s):  
Erik Nielsen
Keyword(s):  
Membrane Trafficking ◽  
Binding Proteins ◽  
Model Organism ◽  
Nucleocytoplasmic Transport ◽  
Small Gtpase ◽  
Gtp Binding Proteins ◽  
Cellular Processes ◽  
Gtp Binding ◽  
Regulatory Module ◽  
Transport Vesicle

Small GTP-binding proteins represent a highly conserved signaling module in eukaryotes that regulates diverse cellular processes such as signal transduction, cytoskeletal organization and cell polarity, cell proliferation and differentiation, intracellular membrane trafficking and transport vesicle formation, and nucleocytoplasmic transport. These proteins function as molecular switches that cycle between active and inactive states, and this cycle is linked to GTP binding and hydrolysis. In this review, the roles of the plant complement of small GTP-binding proteins in these cellular processes are described, as well as accessory proteins that control their activity, and current understanding of the functions of individual members of these families in plants—with a focus on the model organism Arabidopsis—is presented. Some potential novel roles of these GTPases in plants, relative to their established roles in yeast and/or animal systems, are also discussed.

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