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

Abstract

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...

Molecular Determinants of the Ratio of Inert to Infectious Virus Particles

“…175 Recently, the actin modulator drebrin, which interacts with both CXCR4 and actin, has been implicated as a negative regulator of X4 HIV-1 entry. 181 An obligatory cytoskeletal role in the agglomeration of several Env-receptor complexes is compatible with the multioligomeric view of the expanding fusion pore. 176 Future research may elucidate how the endosomal sublocalization of the entry complex, differing from the cell surface in cytoskeletal or membrane conditions, permits progress from hemifusion to pore formation.…”

Pseudorabies virus US3 leads to filamentous actin disassembly and contributes to viral genome delivery to the nucleus

“…We hypothesize that this is due to US3-induced F-actin depolymerization since the F-actin depolymerizing drug cytD significantly increased delivery of the PRV genome at the nucleus. It has been reported for other viruses like HIV and SV40 that entry is associated with local F-actin depolymerization to overcome the cortical actin barrier, located just beneath the plasma membrane (Bukrinsky, 2008;Delorme-Axford and Coyne, 2011;Gordon-Alonso et al, 2013;Taylor et al, 2011;Yoder et al, 2008). Although our current data may suggest that US3 has a similar function during PRV entry, our virus entry assay, which consisted of qPCR-based analysis of viral genome delivery at the nucleus, does not exclude that US3 may play a role in different aspects of viral entry preceding viral genome delivery to the nucleus, including capsid transport along microtubules.…”

Dynamin-2 Stabilizes the HIV-1 Fusion Pore with a Low Oligomeric State

“…Irrespective of the entry method utilized, it is clear that both the actin rearrangement and dynamin-2 (DNM2) activity are required for successful viral infection to occur (Barrero-Villar et al., 2009, Gordón-Alonso et al., 2013). Interestingly, while several reports clearly show the relevance of DNM2 in HIV-1 fusion (Miyauchi et al., 2009a, Pritschet et al., 2012, Sloan et al., 2013), its exact role during virus entry is yet to be clarified.…”