TIP47 is Required for the Production of Infectious HIV-1 Particles from Primary Macrophages

Abstract

Macrophages are among the major targets of HIV-1 infection and play a key role in viral pathogenesis.Identification of the cellular cofactors involved in the production of infectious HIV-1 from macrophages is thus crucial. Here, we investigated the role of the cellular cofactor TIP47 in HIV-1 morphogenesis in primary macrophages. Using siRNA approach, we show that TIP47 is essential for HIV-1 infectivity and propagation. TIP47 silencing disrupts Gag and Env colocalization in macrophages. Moreover, mutations in HIV-1 Gag or Env, which abolish interaction with TIP47, impair HIV-1 propagation and infectivity preventing colocalization of Gag and Env, Gag and Env coimmunoprecipitation. Interestingly, disruption of Gag-TIP47 interaction by matrix mutation or TIP47 depletion also causes Gag to localize in scattered dots in the vicinity of the plasma membrane of macrophages. Therefore, TIP47 is required for the encounter between Gag and Env, and thus for the generation of infectious HIV-1 particles from primary macrophages.

Human Ubc9 Is Involved in Intracellular HIV-1 Env Stability after Trafficking out of the Trans-Golgi Network in a Gag Dependent Manner

“…It has been shown that point mutations in either MA or the CT of Env, that disrupt Env incorporation by altering their direct or indirect interactions at the site of assembly, did not decrease the intracellular levels of Env as was observed in our Ubc9 knockdown cells [97,110–113]. Furthermore, knockdown of Tip47, a host protein reported to be involved in Env incorporation and retrograde transport to the TGN from the PM, did not result in decreased intracellular Env levels [4,26,27]. In addition we did not observe changes in intracellular levels of host cell surface proteins E-cadherin (Figure 3) and TfR (data not shown), both of which also undergo AP-2/clathrin dependent endocytosis [114–116].…”

“…Env and Gag have been hypothesized to first interact and influence each other at an intracellular site, at or near the TGN or recycling endosomes [19,26,27,43]. It is possible that the interruption of normal Gag-Ubc9 interactions in the Ubc9–depleted cells may also affect Gag-Env interactions to lead to a disruption of their co-trafficking to the site of assembly.…”

The Envelope Cytoplasmic Tail of HIV-1 Subtype C Contributes to Poor Replication Capacity through Low Viral Infectivity and Cell-to-Cell Transmission

“…This study also provides evidence that mutations at the Y 802 W 803 diaromatic motif or at the LL 800 dileucine motifs involved in TIP47 and prohibitin binding respectively [54, 121] affect cell-free virus infection but not cell-to-cell propagation [120]. In contrast to this report, we found that both cell-free and cell-to-cell fusion of viruses with subtype C gp41CT were affected, although to different degrees for different viral strains (e.g.…”

“…Endocytosed Env can either proceed to be degraded by lysosomes or be sorted back to the Golgi by interacting with retromer components Vps26 and Vps35 via is1 and is2 [65] or with a number of other proteins which regulate its traffic through the TGN and back to the PM. These include TIP47 through the Y 802 W 803 diaromatic motif [50–54], AP-1 and AP-3 through the Y 712 SPL and the C-terminal dileucine LL 856 motifs [61, 63, 64] and Rab11a/FIP1C and Rab14 through the YW 795 diaromatic motif [55, 66]. AP-2-mediated internalization of Env is reversed by the p55Gag polyprotein precursor, and it was proposed that Env internalization is a means to evade immune recognition and proceeds until sufficient Gag has assembled at the PM to trap Env into the budding virion [67, 68].…”

In Vivo Analysis of Infectivity, Fusogenicity, and Incorporation of a Mutagenic Viral Glycoprotein Library Reveals Determinants for Virus Incorporation

“…Several variations on this model have been proposed. In principle, one or more cellular proteins could serve as adapters to bridge the various viral components together (12,(22)(23)(24), although no specific cellular proteins have been definitively identified to fill this role. Alternatively, interactions with lipid microdomains, such as lipid rafts, could serve as the common element that interacts with both viral components.…”