Identification of a human homologue of the vesicle-associated membrane protein (VAMP)-associated protein of 33 kDa (VAP-33): a broadly expressed protein that binds to VAMP

Weir, M. Lynn; Klip, Amira; Trimble, William S.

doi:10.1042/bj3330247

Cited by 85 publications

(70 citation statements)

References 33 publications

(52 reference statements)

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“…This suggests that the UPR becomes induced in our experiments, and that the ATF6 pathway limits viral replication. NS5A-interacting proteins that modulate HCV replication include VAP-A/B and VPS35, which function in vesicular trafficking (27)(28)(29)(30). VAPA can bind to NS5B as well as hypophosphorylated NS5A and has been proposed to serve as a scaffold for the replication complex within lipid microdomains (31)(32)(33)(34).…”

Section: Discussionmentioning

confidence: 99%

Cellular cofactors affecting hepatitis C virus infection and replication

Randall

Panis²,

Cooper

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

494

453

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Recently identified hepatitis C virus (HCV) isolates that are infectious in cell culture provide a genetic system to evaluate the significance of virus-host interactions for HCV replication. We have completed a systematic RNAi screen wherein siRNAs were designed that target 62 host genes encoding proteins that physically interact with HCV RNA or proteins or belong to cellular pathways thought to modulate HCV infection. This includes 10 host proteins that we identify in this study to bind HCV NS5A. siRNAs that target 26 of these host genes alter infectious HCV production >3-fold. Included in this set of 26 were siRNAs that target Dicer, a principal component of the RNAi silencing pathway. Contrary to the hypothesis that RNAi is an antiviral pathway in mammals, as has been reported for subgenomic HCV replicons, siRNAs that target Dicer inhibited HCV replication. Furthermore, siRNAs that target several other components of the RNAi pathway also inhibit HCV replication. MicroRNA profiling of human liver, human hepatoma Huh-7.5 cells, and Huh-7.5 cells that harbor replicating HCV demonstrated that miR-122 is the predominant microRNA in each environment. miR-122 has been previously implicated in positively regulating the replication of HCV genotype 1 replicons. We find that 2-O-methyl antisense oligonucleotide depletion of miR-122 also inhibits HCV genotype 2a replication and infectious virus production. Our data define 26 host genes that modulate HCV infection and indicate that the requirement for functional RNAi for HCV replication is dominant over any antiviral activity this pathway may exert against HCV.antivirals ͉ miR-122 ͉ RNAi ͉ HCVcc-siRNA H epatitis C virus (HCV) has a notable ability to establish persistent infections in Ϸ70% of cases, resulting in 130 million chronically infected people throughout the world (1). This prevalence has spurred considerable interest in the study of HCV-host interactions, on both cellular and molecular levels. The inability to grow HCV in cell culture led some groups to focus on the identification of cellular proteins that interact with individual HCV proteins or RNA elements, resulting in the accumulation of a large number of putative HCV-host interactions. Unfortunately, the significance of most of these with respect to the HCV life cycle is currently unknown (reviewed in ref.2). Over the past 6 years, cell culture systems have been developed that enable the characterization of HCV replication and entry (3-6). This effort recently culminated in the development of cell culture systems that reproduce the entire viral life cycle (7-9). A number of virus-host interactions have been characterized by using these experimental systems. For example, CD81 has been demonstrated to play a role in HCV entry (10-12).Sequence-specific gene silencing of RNAi is ideal for assessing the genetic phenotypes associated with virus-host interactions. We have previously shown that siRNAs are highly effective at silencing either host or viral RNAs in cells that contain replicating HCV, demonstrating th...

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Section: Discussionmentioning

confidence: 99%

Cellular cofactors affecting hepatitis C virus infection and replication

Randall

Panis²,

Cooper

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

494

453

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“…The first proposed function for VAP arose from its initial identification as an interactor with the membrane fusion protein synaptobrevin/VAMP in Aplysia (5). A role in membrane traffic was further hinted at by other studies in which VAP was found to bind a variety of other membrane fusion proteins (7,12) and where antibodies to VAP inhibited Golgi to ER traffic reconstituted in vitro (9). Like many of the fusion proteins, VAP is a type II tail-anchored protein with a globular amino-terminal domain followed by a stalk region containing a coiled-coil (Fig.…”

mentioning

confidence: 94%

“…VAPs are highly conserved proteins, homologues of which are found in all eukaryotic cells (5)(6)(7)(8)(9)(10)(11). Multiple genes have arisen in many species: in human there are three, VAP-A and -B coded on two separate genes, with the latter having a splice variant, VAP-C; in the budding yeast Saccharomyces cerevisiae there are two VAP homologues.…”

mentioning

confidence: 99%

A Highly Conserved Binding Site in Vesicle-associated Membrane Protein-associated Protein (VAP) for the FFAT Motif of Lipid-binding Proteins

Loewen

Levine

2005

Journal of Biological Chemistry

208

218

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A variety of lipid-binding proteins contain a recently described motif, designated FFAT (two phenylalanines in an acidic tract), which binds to vesicle-associatedmembrane protein-associated protein (VAP). VAP is a conserved integral membrane protein of the endoplasmic reticulum that contains at its amino terminus a domain related to the major sperm protein of nematode worms. Here we have studied the FFAT-VAP interaction in Saccharomyces cerevisiae, where the VAP homologue Scs2 regulates phospholipid metabolism via an interaction with the FFAT motif of Opi1. By introducing mutations at random into Scs2, we found that mutations that abrogated binding to FFAT were clustered in the most highly conserved region. Using site-directed mutagenesis, we identified several critical residues, including two lysines widely separated in the primary sequence. By examining all other conserved basic residues, we identified a third residue that was moderately important for binding FFAT. Modeling VAP on the known structure of major sperm protein showed that the critical residues form a patch on a positively charged face of the protein. In vivo functional studies of SCS22, a second SCS2-like gene in S. cerevisiae, showed that SCS2 was the dominant gene in the regulation of Opi1, with a minor contribution from SCS22. We then established that reduction in the affinity of Scs2 mutants for FFAT correlated well with loss of function, indicating the importance of these residues for binding FFAT motifs. Finally, we found that human VAP-A could substitute for Scs2 but that it functioned poorly, suggesting that other factors modulate the binding of Scs2 to proteins with FFAT motifs.

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“…This mutation is predicted to introduce a kink between two short stretches of β strands, and causes insolubility and accumulation of large ER aggregates in cells (Kanekura et al, 2006). The VAPA and VAPB genes are broadly expressed (Nishimura et al, 1999;Weir et al, 1998), suggesting they perform a function required by all cells. VAPA is primarily localised to the early secretory pathway where it colocalises with ER markers and microtubules (Skehel et al, 2000), but it is also found in tight junctions, late secretory and synaptic vesicles (Lapierre et al, 1999;Nishimura et al, 1999;Pennetta et al, 2002;Weir et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…The VAPA and VAPB genes are broadly expressed (Nishimura et al, 1999;Weir et al, 1998), suggesting they perform a function required by all cells. VAPA is primarily localised to the early secretory pathway where it colocalises with ER markers and microtubules (Skehel et al, 2000), but it is also found in tight junctions, late secretory and synaptic vesicles (Lapierre et al, 1999;Nishimura et al, 1999;Pennetta et al, 2002;Weir et al, 1998). Although studies have implicated VAPA in late secretory events, its localisation in the ER suggests a more prominent role in early secretory compartments.…”

Section: Introductionmentioning

confidence: 99%

FFAT rescues VAPA-mediated inhibition of ER-to-Golgi transport and VAPB-mediated ER aggregation

Prosser

Tran

Gougeon

et al. 2008

Journal of Cell Science

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The VAMP-associated proteins termed VAP are a small gene family of proteins characterised by the presence of an N-terminal major sperm protein (MSP) domain. The P56S mutation of the B isoform (VAPB) has been linked to late-onset amyotrophic lateral sclerosis (ALS8) and its expression causes formation of large ER aggregates. Overexpression of the wild-type A isoform (VAPA) but not the B isoform (VAPB), inhibited ER-to-Golgi transport of membrane proteins. This transport block by VAPA was primarily due to decreased segregation of membrane cargo into ER vesicles. We also found that VAPA inhibited lateral diffusion of membrane proteins, most likely through its stable association with microtubules. The MSP domain of VAP is known to interact with the FFAT motif (two phenylalanines in an acidic tract) of proteins involved in sterol regulation. Overexpression of FFAT restored ER-to-Golgi transport and lateral diffusion of membrane proteins, and resolved the large ER aggregates in VAPB-P56S. Application of a FFAT peptide restored in vitro ER vesicle budding and disrupted VAP-microtubule association. Thus, overexpression of the two VAP isoforms causes retention of ER membrane proteins by impeding lateral diffusion and their incorporation into transport vesicles. This inhibitory effect can be relieved by expression of the FFAT motif.

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Identification of a human homologue of the vesicle-associated membrane protein (VAMP)-associated protein of 33 kDa (VAP-33): a broadly expressed protein that binds to VAMP

Cited by 85 publications

References 33 publications

Cellular cofactors affecting hepatitis C virus infection and replication

Cellular cofactors affecting hepatitis C virus infection and replication

A Highly Conserved Binding Site in Vesicle-associated Membrane Protein-associated Protein (VAP) for the FFAT Motif of Lipid-binding Proteins

FFAT rescues VAPA-mediated inhibition of ER-to-Golgi transport and VAPB-mediated ER aggregation

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