A natural variability in the proline-rich motif of Nef modulates HIV-1 replication in primary T cells

Abstract

In the infected host, the Nef protein of HIV/SIV is required for high viral loads and thus disease progression. Recent evidence indicates that Nef enhances replication in the T cell compartment after the virus is transmitted from dendritic cells (DC). The underlying mechanism, however, is not clear. Here, we report that a natural variability in the proline-rich motif (R71T) profoundly modulated Nef-stimulated viral replication in primary T cells of immature dendritic cell/T cell cocultures. Whereas both Nef variants (R/T-Nef) downregulated CD4, only the isoform supporting viral replication (R-Nef) efficiently interacted with signaling molecules of the T cell receptor (TCR) environment and stimulated cellular activation. Structural analysis suggested that the R to T conversion induces conformational changes, altering the flexibility of the loop containing the PxxP motif and hence its ability to bind cellular partners. Our report suggests that functionally and conformationally distinct Nef isoforms modulate HIV replication on the interaction level with the TCR-signaling environment once the virus enters the T cell compartment.

The HIV-1 Pathogenicity Factor Nef Interferes with Maturation of Stimulatory T-lymphocyte Contacts by Modulation of N-Wasp Activity

“…These target T-cells are fully permissive for HIV replication despite the lack of classical T-cell activation markers, suggesting that Nef selectively induces a low state of activation. Importantly, mutation of the Nef PXXP motif blunts its ability to boost HIV-1 replication in co-cultures of immature dendritic cells and autologous T-lymphocytes (51) and prevents the modulation of TCR-induced actin remodeling (this study). We therefore hypothesize that this newly identified modulation of IS maturation helps Nef to generate a moderate TCR signal optimized for HIV-1 production.…”

Human Immunodeficiency Virus Type 1 Nef Activates p21-Activated Kinase via Recruitment into Lipid Rafts

“…Importantly, Nef-mediated increase of the cellular activation state can be detected in target T cells already prior to integration of the incoming viral genome (72). Such activation was recently shown to be relevant in a primary cell coculture model of immature dendritic cells and autologous T cells, where efficient virus replication requires Nef and correlates with its ability to induce signaling (25,45,50).…”

“…Importantly, the PxxP motif of Nef that is a prerequisite for Pak activation is required for the optimal spread of HIV in primary cells (25,44,58). Furthermore, one study reported a correlation between the association of Nef with Pak activity and disease progression in SIV-infected macaques (61).…”

Nef Binds p6* in GagPol during Replication of Human Immunodeficiency Virus Type 1

“…Moreover, Nef activates signaling cascades that increase levels of viral replication in primary T cells (11,14,44). Finally, Nef increases levels of Gag in detergent-resistant microdomains (lipid rafts) at the plasma membrane to enhance the infectivity of progeny virions (53).…”