Two independent regions of HIV-1 Nef are required for connection with the endocytic pathway through binding to the mu 1 chain of AP1 complex

The Nef protein from the human immunodeficiency virus (HIV) induces down-re gulation of the CD4 and major histocompatibility complex class I molecules from the cell surface by interfering with the endocytic machinery. This wor k focuses on the interaction of HIV-1 Nef with the mu1 chain of adaptor pro tein type 1 (AP1) complex and its contribution to the Nef-induced alteratio ns of membrane trafficking. Two independent regions surrounding a disordere d loop located in the C-terminal part of Nef are involved in mu1 binding. E ach region can separately interact with mu1, and simultaneous point mutatio ns within both regions are needed to abolish binding. We used CD8 chimeras in which the cytoplasmic tail was replaced by Nef mutants to show that thes e mu1-binding sites contain determinants required to induce CD4 down-regula tion and to target the chimera to the endocytic pathway by promoting AP1 co mplex recruitment. Ultrastructural analysis revealed that the CD8-Nef chime ra provokes morphological alterations of the endosomal compartments and co- localizes with AP1 complexes. These data indicate that the recruitment by N ef of AP1 via binding to mu1 participates in the connection of Nef with the endocytic pathway.