JCB：Rab27a蛋白控制HIV-1包装

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病毒HIV-1的复制需要病毒组分向免疫细胞的细胞膜开启协调性的运动，而在免疫细胞中病毒粒子就可以装配并且最终释放，近日一篇刊登在国际杂志The Journal of Cell Biology上的研究论文中，来自布宜诺斯艾利斯大学的科学家通过研究揭示了控制胞内运输的蛋白Rab如何通过促进产生高水平的膜脂质来支持HIV-1的装配。

在细胞膜特殊位点新装配形成的HIV-1颗粒往往会富含PIP2，PIP2是细胞膜的磷脂组分，其可以补充名为Pr55Gag (Gag)的病毒蛋白，这种病毒蛋白就可以指导HIV-1的装配；目前研究者已经解析了该过程需要的特殊细胞分泌通路，而本文中研究者调查了是否Rab27a蛋白也扮演了类似的功能，该蛋白可以指导内含体向细胞膜的运输。

文章中，研究者发现HIV-1的复制在缺失Rab27a蛋白的免疫细胞中处于受损状态，而这些免疫细胞的细胞膜中PIP2的水平也下降了，而且不能够补充Gag蛋白来形成病毒的装配位点；于是研究者就表明，Rab27a蛋白可以通过控制酶类内含体的运输从而促进细胞膜中PIP2的形成，而酶类内含体的运输对于细胞外周脂质的形成非常必要。

最后研究者认为，本文的研究成果为后期调查是否控制内含体的运输可以作为一种新型抗HIV-1的疗法提供了新的研究线索，同时也为揭示HIV-1的感染机体提供了一定的帮助。

（生物谷Bioon.com）

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.

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Rab27a controls HIV-1 assembly by regulating plasma membrane levels of phosphatidylinositol 4,5-bisphosphate

Pehuén Pereyra Gerber,1,* Mercedes Cabrini,1,* Carolina Jancic,2 Luciana Paoletti,3 Claudia Banchio,3 Catalina von Bilderling,4 Lorena Sigaut,5 Lía I. Pietrasanta,5 Gabriel Duette,1 Eric O. Freed,6 Genevieve de Saint Basile,7,8 Catarina Ferreira Moita,9 Luis Ferreira Moita,9 Sebastian Amigorena,10 Philippe Benaroch,10 Jorge Geffner,1 and Matías Ostrowski1

During the late stages of the HIV-1 replication cycle, the viral polyprotein Pr55Gag is recruited to the plasma membrane (PM), where it binds phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and directs HIV-1 assembly. We show that Rab27a controls the trafficking of late endosomes carrying phosphatidylinositol 4-kinase type 2 α (PI4KIIα) toward the PM of CD4+ T cells. Hence, Rab27a promotes high levels of PM phosphatidylinositol 4-phosphate and the localized production of PI(4,5)P2, therefore controlling Pr55Gag membrane association. Rab27a also controls PI(4,5)P2 levels at the virus-containing compartments of macrophages. By screening Rab27a effectors, we identified that Slp2a, Slp3, and Slac2b are required for the association of Pr55Gag with the PM and that Slp2a cooperates with Rab27a in the recruitment of PI4KIIα to the PM. We conclude that by directing the trafficking of PI4KIIα-positive endosomes toward the PM, Rab27a controls PI(4,5)P2 production and, consequently, HIV-1 replication.

http://jcb.rupress.org/content/early/2015/04/27/jcb.201409082
原文：http://pan.baidu.com/s/1i31T1EP

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

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marine0425030 发表于 2015-5-7 12:45
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 ...

这种科研思维是正常的。很多病毒劫持和利用宿主的分泌系统来实现病毒粒子的包装和释放。因此参与这一过程的宿主蛋白就很有可能参与调控病毒的产生。另一个例子就是IFITM家族蛋白分子了，参与调控多种病毒感染的早期过程。就Rab27a来说，我觉得对于那些在膜上进行组装的病毒如流感，其作用可能就不是很大。