Specific binding of HIV-1 envelope protein gp120 to the structural membrane proteins ezrin and moesin

The observation that HIV in vitro can infect CD4-and Gal-C-negative brain cell lines has stimulated this study to identify alternative gp120-binding proteins on brain cells. HIV-1 gp120 binding proteins of the CD4-negative and Gal-C-negative, non-productively infectable human glioblastoma cell line D54 were purified by affinity chromatography over a gp120-conjugated sepharose column and identified by peptide microsequencing. The binding capacity and specificity of this column was controlled using extracts of CD4-positive cells. Two of seven prominent proteins eluted from the gp120 affinity column specifically bound gp120 in Western blot overlay experiments and were identified by subsequent immunoblotting and microsequencing as ezrin and moesin, members of the ERM (ezrin, radixin, moesin) family of cellular structural membrane proteins. Antibodies to ezrin and moesin specifically recognized the eluted gp120 binding proteins confirming their identification. Ezrin and moesin are structural proteins binding to the cellular membrane and to several cytoskeletal and transmembrane proteins. Our results suggest that ezrin and moesin might play a role as gp160/gp120 binding proteins during the uptake, the assembly or the budding of HIV.