THE INTRACYTOPLASMIC DOMAIN OF GP41 MEDIATES POLARIZED BUDDING OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 IN MDCK CELLS

Human immunodeficiency virus type 1 (HIV-1) has been shown to exhibit a specific basolateral release in polarized epithelial cells. Previous investigators have used vaccinia virus recomi,inants expressing HIV p roteins to demonstrate that virus release is nonpolarized in the absen ce of viral envelope glycoproteins. In this study, we developed a tran sient expression system which allows the use of Madin-Darby canine kid ney polarized epithelial cells directly grown on semipermeable membran es. This procedure allowed us to investigate polarized HIV viral buddi ng following introduction of proviral DNA constructs. Expression of en v gene products in trans demonstrated the ability to polarize env-nega tive viruses in a dose dependent manner. The targeting signal for pola rized virus release was shown to be present in the envelope gp41 trans membrane protein and absent from the gp120 portion of env. At least pa rt of this signal is within the gp41 intracytoplasmic domain. Mutants of the p17(gag) matrix protein were shown to be nonpolarized only when unable to interact with the envelope glycoproteins. Together, these d ata are consistent with a model of polarized virus budding in which ca psid proteins, lacking a targeting signal, are targeted for specific b asolateral release via an interaction of p17 with the envelope glycopr otein containing the polarization signal in its intracytoplasmic domai n.