Blockade of human immunodeficiency virus type 1 expression by caveolin-1

Caveolin-1 (Cav-1) is a major protein constituent of caveolae, a type of plasma membrane raft. We observed that coexpression of human Cav-1 with human immunodeficiency virus type 1 (HIV-1) blocked virion production from cells that are ordinarily highly permissive. Further investigation showed that this effect is specific, occurs at low ratios of Cav-1 to HIV-1 DNA, depends on expression of Cav-1 protein, and involves severely impaired expression of HIV-1 proteins. Cav-1 also blocked HIV-2 expression. In contrast, Cav-1 did not inhibit protein expression by a paramyxovirus and did not induce apoptosis or affect cellular morphology, cell viability, or cell cycle progression. Although only small amounts of HIV-1 virions were released from Cav-1-transfected cells, these were fully infectious. Deletion mutagenesis showed that the C-terminal 78 residues were as active as the full-length (178-amino-acid) protein in producing the block. In contrast, the 100 most N-terminal amino acids of Cav-1, which include the previously identified oligomerization and scaffolding domains, were shown to be dispensable. Study of single-amino-acid-exchange mutants of Cav-1 established that palmitoylation was not required. Additional deletion mutants then identified the hydrophobic, membrane-associated domain (residues 101 to 135) as the main determinant. Cellular distribution of wild-type and mutant proteins correlated with ability to block HIV-1 expression. Finally, Cav-2 also blocked HIV-1 expression. These data show that coexpression of caveolins can markedly inhibit expression of HIV proviral DNA and establish that the inhibition is mediated by the hydrophobic, membrane-associated domain.