JCB：Rab27a蛋白控制HIV-1包装

marine0425030

JCB评论原文


Rab27a builds a platform for HIV-1

Compared with a control T cell (left), knocking down Rab27a blocks the delivery of late endosomes (red) to the plasma membrane, inhibiting the recruitment of Pr55Gag (green) to HIV-1 assembly sites.

The endosomal trafficking protein Rab27a supports HIV-1 replication by promoting PI(4,5)P2 production at the plasma membrane (PM), Pereyra Gerber et al. reveal.

New HIV-1 particles assemble at specialized PM domains that are enriched in the phospholipid PI(4,5)P2 and recruit the viral polyprotein Pr55Gag. Because endosomal trafficking has been implicated in viral assembly and release, Pereyra Gerber et al. investigated whether HIV-1 replication was controlled by Rab27a, a small GTPase that promotes the delivery of late endosomes and multivesicular bodies to the PM.

Viral replication was impaired in T cells lacking Rab27a, the researchers found. These cells showed reduced levels of PI(4,5)P2at the PM and thus failed to recruit Pr55Gag to form viral assembly sites. Knocking down Rab27a also suppressed PI(4,5)P2production and viral replication in macrophages, which normally recruit Pr55Gag to PM invaginations called virus-containing compartments.

Rab27a boosted PI(4,5)P2 production at the PM by delivering the late endosome-associated lipid kinase PI4KIIα, which generates the PI(4,5)P2 precursor PI(4)P. Several Rab27a effectors were also required for HIV-1 replication. T cells lacking the endosomal docking protein Slp2a, for example, also failed to deliver PI4KIIα to the PM to promote PI(4,5)P2 production and Pr55Gag recruitment.

Senior author Matías Ostrowski says that these results open a path to investigate whether manipulating endosomal traffic could be a new target for anti–HIV-1 therapies. He now wants to investigate how endosomes carrying PI4KIIα fuse with the PM once they have been docked there by Rab27a and its effectors.

marine0425030

一个idea的产生，它不是从天而降的，也许在其他研究上也有相同的机制。
也许当时他老板就说：嗨，要不咱也试试这个蛋白。然后故事就从这里开始啦。

Rab27a蛋白相关研究

1.Role of the small GTPase Rab27a during Herpes simplex virus infection of oligodendrocytic cells

Background

The morphogenesis of herpes simplex virus type 1 (HSV-1) comprises several events, of which some are not completely understood. It has been shown that HSV-1 glycoproteins accumulate in the trans-Golgi network (TGN) and in TGN-derived vesicles. It is also accepted that HSV-1 acquires its final morphology through a secondary envelopment by budding into TGN-derived vesicles coated with viral glycoproteins and tegument proteins. Nevertheless, several aspects of this process remain elusive. The small GTPase Rab27a has been implicated in regulated exocytosis, and it seems to play a key role in certain membrane trafficking events. Rab27a also seems to be required for human cytomegalovirus assembly. However, despite the involvement of various Rab GTPases in HSV-1 envelopment, there is, to date, no data reported on the role of Rab27a in HSV-1 infection.

Results

Herein, we show that Rab27a colocalized with GHSV-UL46, a tegument-tagged green fluorescent protein-HSV-1, in the TGN. In fact, this small GTPase colocalized with viral glycoproteins gH and gD in that compartment. Functional analysis through Rab27a depletion showed a significant decrease in the number of infected cells and viral production in Rab27a-silenced cells.

Conclusions

Altogether, our results indicate that Rab27a plays an important role in HSV-1 infection of oligodendrocytic cells.

Keywords: HSV-1; Oligodendrocytes; Rab27a; Viral egress; Morphogenesis; Tegument

2.Rab27a Is Required for Human Cytomegalovirus Assembly

Human cytomegalovirus (HCMV) completes its final envelopment on intracellular membranes before it is released from the cell. The mechanisms underlying these processes are not understood. Here we studied the role of Rab27a, a regulator of lysosome-related organelle transport, in HCMV production. HCMV infection increased Rab27a expression, and recruitment of Rab27a to membranous strutures at the assembly site. Immuno-gold labelling demonstrated association of Rab27a with viral envelopes. CMV production was reduced after knock-down of Rab27a, and in Rab27a-deficient ashen melanocytes. This study shows a requirement for Rab27a in the CMV life cycle and suggests that CMV and LRO biogenesis share common molecular mechanisms.

3.Regulation of hepatitis C virus secretion by the Hrs-dependent exosomal pathway

Abstract

The molecular mechanisms of assembly and budding of hepatitis C virus (HCV) remain poorly understood. The budding of several enveloped viruses requires an endosomal sorting complex required for transport (ESCRT), which is part of the cellular machinery used to form multivesicular bodies (MVBs). Here, we demonstrated that Hrs, an ESCRT-0 component, is critical for the budding of HCV through the exosomal secretion pathway. Hrs depletion caused reduced exosome production, which paralleled with the decrease of HCV replication in the host cell, and that in the culture supernatant. Sucrose-density gradient separation of the culture supernatant of HCV-infected cells revealed the co-existence of HCV core proteins and the exosome marker. Furthermore, both the core protein and an envelope protein of HCV were detected in the intraluminal vesicles of MVBs. These results suggested that HCV secretion from host cells requires Hrs-dependent exosomal pathway in which the viral assembly is also involved.

4.Hepatitis E virus egress depends on the exosomal pathway, with secretory exosomes derived from multivesicular bodies