Background: In HIV-1 viral fusion and infection, F-actin is required for CD4-co-receptor redistribution in viral cell contact areas, but little is known about the molecular mechanisms un- derlying this fundamental process. We investigated whether HIV-1 Env might promote viral entry by activating ERM (ezrin- radixin-moesin) proteins in a PI4P5-K Ialpha-mediated PIP2 production-dependent manner to regulate F-actin reorganization and CD4/co-receptors clustering and direct interaction. Observations: In this study, we show that HIV-1 virus promotes pore fusion formation and viral infection by inducing PIP2 pro- duction. This process appeared to be mediated by the PI4P5-K Ia kinase. Over-expression of wtPI4P5-K Ia increased HIV-1 Env-mediated PIP2 production and enhanced viral fusion and replication, in permissive lymphocytes. PIP2 production and HIV-1 infection were reduced in cells over-expressing the kinase-dead mutant D227A (D/A)-PI4P5-K Ia, or after knock- down of endogenous PI4P5-K Ia. Moreover, X4-tropic HIV-1 viral fusion and infection required the activation of moesin, an actin adaptor protein of the ERM family, in a PIP2-dependent manner. HIV-1-gp120-induced CD4/CXCR4 association and clustering, occurred during early viral entry, and required moesin-mediat- ed plasma membrane-actin anchoring. Suppression of moesin impeded HIV-1-envelope-mediated F-actin reorganization, CD4/ CXCR4 clustering and interaction, and inhibits HIV-1 entry and infection in lymphocytes. Remarkably, moesin-specific silencing or a dominant-negative construct alters the trafficking of nascent endocytic clatrhin-coated vesicles, which accumulates near the plasma membrane carrying the TfR receptor. Conclusions: · PI4P5-K Ialpha-mediated PIP2 production is involved in the regulation of HIV-1 viral infection. · Moesin is involved in the control of trafficking of CCVs and activated moesin promotes F-actin redistribution and CD4/CXCR4 clus- tering is required for X4-tropic HIV-1 infection in permissive lymphocytes.
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