Retroviral Assembly and Budding Occur through an Actin-Driven Mechanism

Gladnikoff, Micha; Shimoni, Eyal; Gov, Nir S.; Rousso, Itay

doi:10.1016/j.bpj.2009.08.016

Cited by 87 publications

(103 citation statements)

References 36 publications

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“…The observation of dense F-actin networks in the close vicinity of and often pointing toward viral buds in our cET study (21) as well as the AFM results showing asters at HIV-1 budding sites presumed to represent F-actin cables (15) suggested an active involvement of F-actin in HIV-1 assembly and/or release. Moreover, Gladnikoff et al (15) reported that these asters were dependent on the presence of the NC domain in Gag and were not observed for Gag(LZ).…”

Section: Discussionsupporting

confidence: 60%

“…Mutational analyses showed that F-actin binding to the NC domain did not require the interaction of this domain with the viral RNA (13,14). A role of the NC domain in F-actin recruitment was supported by an investigation of viral budding sites at the surface of HIV-1 and murine leukemia virus (MLV) Gag-expressing HeLa and NIH 3T3 cells by atomic force microscopy (AFM) (15). That study reported prominent star-shaped structures ("asters") with arm lengths of ϳ0.5 to 2.5 m centered at a subset of budding sites.…”

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confidence: 99%

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The Nucleocapsid Domain of Gag Is Dispensable for Actin Incorporation into HIV-1 and for Association of Viral Budding Sites with Cortical F-Actin

Stauffer

Rahman

Marco

et al. 2014

J Virol

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Actin and actin-binding proteins are incorporated into HIV-1 particles, and F-actin has been suggested to bind the NC domain in HIV-1 Gag. Furthermore, F-actin has been frequently observed in the vicinity of HIV-1 budding sites by cryo-electron tomography (cET). Filamentous structures emanating from viral buds and suggested to correspond to actin filaments have been observed by atomic force microscopy. To determine whether the NC domain of Gag is required for actin association with viral buds and for actin incorporation into HIV-1, we performed comparative analyses of virus-like particles (VLPs) obtained by expression of wild-type HIV-1 Gag or a Gag variant where the entire NC domain had been replaced by a dimerizing leucine zipper [Gag(LZ)]. The latter protein yielded efficient production of VLPs with near-wild-type assembly kinetics and size and exhibited a regular immature Gag lattice. Typical HIV-1 budding sites were detected by using cET in cells expressing either Gag or Gag(LZ), and no difference was observed regarding the association of buds with the F-actin network. Furthermore, actin was equally incorporated into wild-type HIV-1 and Gag-or Gag(LZ)-derived VLPs, with less actin per particle observed than had been reported previously. Incorporation appeared to correlate with the relative intracellular actin concentration, suggesting an uptake of cytosol rather than a specific recruitment of actin. Thus, the NC domain in HIV-1 Gag does not appear to have a role in actin recruitment or actin incorporation into HIV-1 particles. IMPORTANCEHIV-1 particles bud from the plasma membrane, which is lined by a network of actin filaments. Actin was found to interact with the nucleocapsid domain of the viral structural protein Gag and is incorporated in significant amounts into HIV-1 particles, suggesting that it may play an active role in virus release. Using electron microscopy techniques, we previously observed bundles of actin filaments near HIV-1 buds, often seemingly in contact with the Gag layer. Here, we show that this spatial association is observed independently of the proposed actin-binding domain of HIV-1. The absence of this domain also did not affect actin incorporation and had a minor effect on the viral assembly rate. Furthermore, actin was not enriched in the virus compared to the average levels in the respective producing cell. Our data argue against a specific recruitment of actin to HIV-1 budding sites by the nucleocapsid domain of Gag.

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Section: Discussionsupporting

confidence: 60%

mentioning

confidence: 99%

The Nucleocapsid Domain of Gag Is Dispensable for Actin Incorporation into HIV-1 and for Association of Viral Budding Sites with Cortical F-Actin

Stauffer

Rahman

Marco

et al. 2014

J Virol

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“…Is actin dynamics regulated by HIV for promoting budding and virion release? 125 These questions remain to be addressed.…”

mentioning

confidence: 99%

“…[87][88][89] Actin and actin-binding proteins are found inside HIV-1 virions 15,121 raising the question of a potential role of actin cytoskeleton dynamic in either Gag trafficking or in virion budding. 20,[122][123][124][125] The Gag NC domain of several retroviruses (HIV, MLV, EIAV) is known to interact with actin. Indeed, Gag multimerization is required for filamentous actin-Gag association during EIAV assembly.…”

mentioning

confidence: 99%

Properties and functions of the nucleocapsid protein in virus assembly

2010

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“…The actin cytoskeleton is known to be involved in several steps of the HIV-1 cycle, including entry (18,20,24), nucleocapsid transport toward the host nucleus (25,26), and viral assembly and budding (11,27,28). Some recent reports suggest that although F-actin polymerization is needed for receptor clustering, it causes a physical restriction for the following nucleocapsid entry (26,29 of the actin-severing protein cofilin has been associated with enhanced HIV entry (26).…”

Section: Hiv-1 Contact With Target Cells Triggers F-actin Rearrangemementioning

confidence: 99%

Actin-binding Protein Drebrin Regulates HIV-1-triggered Actin Polymerization and Viral Infection

Gordon-Alonso

Rocha-Perugini

Álvarez

et al. 2013

Journal of Biological Chemistry

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Background: Drebrin binds to F-actin and CXCR4 in T cells. Thus, it is a potential candidate for the modulation of HIV-1 infection. Results: Drebrin and CXCR4 accumulate at viral attachment areas. Drebrin knockdown decreases F-actin polymerization, and increases local profilin accumulation and HIV-1 infection. Conclusion: Drebrin inhibits HIV-1 entry by stabilizing HIV-1-triggered F-actin polymerization. Significance: Modulation of actin dynamics differentially regulates each viral step for an effective viral infection. HIV-1 contact with target cells triggers F-actin rearrangements that are essential for several steps of the viral cycle. Successful HIV entry into CD4؉ T cells requires actin reorganization induced by the interaction of the cellular receptor/co-receptor complex CD4/CXCR4 with the viral envelope complex gp120/gp41 (Env).In this report, we analyze the role of the actin modulator drebrin in HIV-1 viral infection and cell to cell fusion. We show that drebrin associates with CXCR4 before and during HIV infection. Drebrin is actively recruited toward cellvirus and Env-driven cell to cell contacts. After viral internalization, drebrin clustering is retained in a fraction of the internalized particles. Through a combination of RNAi-based inhibition of endogenous drebrin and GFP-tagged expression of wild-type and mutant forms, we establish drebrin as a negative regulator of HIV entry and HIV-mediated cell fusion. Down-regulation of drebrin expression promotes HIV-1 entry, decreases F-actin polymerization, and enhances profilin local accumulation in response to HIV-1. These data underscore the negative role of drebrin in HIV infection by modulating viral entry, mainly through the control of actin cytoskeleton polymerization in response to HIV-1.Human immunodeficiency virus (HIV)-1 entry requires fusion between the viral envelope and the plasma membrane of the target cell (1). This process is mediated by the viral envelope glycoprotein complex gp120/gp41 (Env), 5 which interacts first with CD4 and then with a co-receptor, one of the chemokine receptors CCR5 or CXCR4 (2, 3).For the viral and cellular membranes to fuse, a critical number of gp120-CD4/coreceptor engagements are needed to establish an energetically productive fusion pore (4). HIV-1 can also be transmitted from infected to uninfected cells through cell to cell contacts, called virological synapses because of their similarities to the immunological synapse (5). As an example, CD4 and CXCR4 recruitment (6 -8) and local actin polymerization take place in both processes (6, 9 -11). Receptor clustering is regulated by two main factors: 1) insertion into specific membrane domains by lateral membrane receptor interactions (12) such as lipid rafts (13) or tetraspanin-enriched microdomains (14 -17); and 2) actin remodeling (6, 18 -20). This phenomenon is well illustrated by experiments in which HIV-1 contact induces CD4 and CXCR4 capping at the plasma membrane of target CD4 ϩ T lymphocytes (21,22). Receptor capping requires the formation of a subcortical...

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Retroviral Assembly and Budding Occur through an Actin-Driven Mechanism

Cited by 87 publications

References 36 publications

The Nucleocapsid Domain of Gag Is Dispensable for Actin Incorporation into HIV-1 and for Association of Viral Budding Sites with Cortical F-Actin

The Nucleocapsid Domain of Gag Is Dispensable for Actin Incorporation into HIV-1 and for Association of Viral Budding Sites with Cortical F-Actin

Properties and functions of the nucleocapsid protein in virus assembly

Actin-binding Protein Drebrin Regulates HIV-1-triggered Actin Polymerization and Viral Infection

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