Human immunodeficiency virus type 1 VPU protein affects Sindbis virus glycoprotein processing and enhances membrane permeabilization

The human immunodeficiency virus type 1 (HIV-1) Vpu is an integral membrane protein that forms oligomeric structures in membranes. Expression of vpu using Sindbis virus (SV) as a Vector leads to permeabilization of plasma membrane to hydrophilic molecules and impaired maturation of wild type SV glycoproteins in BHK cells. The 6K protein is a membrane protein encoded in the SV genome that facilitates budding of virus particles and regulates transport of viral glycoproteins through the secretory pathway. Some of these functions were assayed with a SV mutant containing a partially deleted 6K gene. Transfection of BHK cells with pSV Delta 6K vector rendered defective SV Delta 6K virus, which had lower membrane permeabilization, impaired glycoprotein processing, and deficient Virion budding. Replacement of 6K function by HIV-1 Vpu in SV Delta 6K was tested by cloning the vpu gene under a duplicated late promoter (pSV Delta 6KVpu). The presence of the vpu gene in the GK-deleted virus enhances membrane permeability, modifies glycoprotein precursor processing, and facilitates infectious virus particle production. Restoration of infectivity of GK-deleted SV by Vpu was evidenced by increased PFU production and cytopathic effect on infected cells. The modification of SV Delta 6K glycoprotein maturation by Vpu was reflected in augmented processing of B precursor and impairment of PE2 cleavage. Taken together, our data support the notion that HIV-1 Vpu and SV 6K proteins share some analogous functions. (C) 2001 Academic Press.