Background: HIV-1 release requires functional interaction between the L domain p6 and the host protein TSG101. Other cellular proteins in the vacuolar protein sorting pathway are also likely involved in HIV-1 release. However, the contribution of other host proteins in the process of HIV-1 budding remains to be defined. In this study, we provide several lines of evidences to suggest that Vps28 play an important role in HIV-1 release.

Methods and Results: Expression of TSG101 mutant lacking the Vps28 interaction domain but maintained all the other functional domains inhibited HIV-1 release. Reducing intracellular Vps28 expression by siRNA also inhibited HIV-1 release. Co-immunoprecipitation experiments suggest that HIV-1 Gag molecules interacted with Vps28 in viral expressing cells. Vps28 molecules competent for interaction with TSG101 were incorporated into HIV-1 virions whereas Vps28 mutant failed to interact with TSG101 was not incorporated into HIV-1 virions. Expression of Vps28 mutant that lacked the C-terminal domain but competent for TSG101 binding significantly inhibited HIV-1 release.

Conclusions: Our data suggest that Vps28 is essential for HIV-1 release. Vps28, TSG101, and possibly other interacting cellular proteins may play important roles during HIV-1 release.