Retroviral Env Glycoprotein Trafficking and Incorporation into Virions

Figure 1

Synthesis and trafficking of HIV-1 Gag and Env proteins. Precursor Gag (Pr55^Gag) (left) is synthesized on cytosolic ribosomes and traffics to the plasma membrane (PM), where it forms multimers (middle). Env is synthesized as the gp160 precursor, and undergoes glycosylation and oligomerization in the RER. Oligomerized gp160 is transported to the Golgi and the TGN, where it is processed into the surface glycoprotein gp120 and the transmembrane glycoprotein gp41 by cellular enzymes. The gp120/gp41 complexes are transported through the secretory pathway to the PM and are incorporated into virus particles (middle). At the PM, most of the Env protein is endocytosed into early endosomes (EE), which mature into late endosomes (LE) and then into lysosomes for Env degradation (right). However, some Env proteins are recycled to the PM through recycling endosomes (RE). During and after virus release, processing of Pr55^Gag by virus proteases yields mature virions. The protein domains of Pr55^Gag and Env are illustrated in the insert at the top left. The illustration was adapted from Checkley et al. with permission from Elsevier [23].