Rab11-FIP1C and Rab14 Direct Plasma Membrane Sorting and Particle Incorporation of the HIV-1 Envelope Glycoprotein Complex

Abstract

The incorporation of the envelope glycoprotein complex (Env) onto the developing particle is a crucial step in the HIV-1 lifecycle. The long cytoplasmic tail (CT) of Env is required for the incorporation of Env onto HIV particles in T cells and macrophages. Here we identify the Rab11a-FIP1C/RCP protein as an essential cofactor for HIV-1 Env incorporation onto particles in relevant human cells. Depletion of FIP1C reduced Env incorporation in a cytoplasmic tail-dependent manner, and was rescued by replenishment of FIP1C. FIP1C was redistributed out of the endosomal recycling complex to the plasma membrane by wild type Env protein but not by CT-truncated Env. Rab14 was required for HIV-1 Env incorporation, and FIP1C mutants incapable of binding Rab14 failed to rescue Env incorporation. Expression of FIP1C and Rab14 led to an enhancement of Env incorporation, indicating that these trafficking factors are normally limiting for CT-dependent Env incorporation onto particles. These findings support a model for HIV-1 Env incorporation in which specific targeting to the particle assembly microdomain on the plasma membrane is mediated by FIP1C and Rab14.

Biochemical evidence of a role for matrix trimerization in HIV-1 envelope glycoprotein incorporation

“…For HIV-1, the CT is required for Env incorporation into particles in physiologically relevant cell types, such as peripheral blood mononuclear cells, monocyte-derived macrophages, and most T-cell lines (8,9). Recent work has shown that the CT mediates an interaction with Rab11 familyinteracting protein 1c (FIP1c), which in turn interacts with Rab14 and appears to direct trafficking of HIV-1 Env to sites of assembly; it is likely that interactions with FIP1c contribute to the observed requirement for the CT in Env incorporation (10,11). It is, however, unclear why lentiviral CTs are so large, because far smaller Env CTs also contain essential functional trafficking and signaling motifs (12).…”

Structure-Function Analyses of the Interactions between Rab11 and Rab14 Small GTPases with Their Shared Effector Rab Coupling Protein (RCP)

“…In Qi et al (35), Ser-580 and Ser-582 were mutated to asparagine and leucine, respectively, to match the residues of the corresponding positions in FIP2 (Fig. 5B) (35). However, inspection of this region revealed that the amino acid in FIP2, which aligns with Ser-582 of RCP, is in fact a phenylalanine and not a leucine (Fig.…”

“…5A) were subjected to an overlay assay with GST-Rab11A and GST-Rab14 to further clarify the Rab-binding region. In Qi et al (35), Ser-580 and Ser-582 were mutated to asparagine and leucine, respectively, to match the residues of the corresponding positions in FIP2 (Fig. 5B) (35).…”

“…However, more recently, a study by Goldenring, Spearman, and co-workers (23) reported that Rab14 does indeed bind to RCP, but via a region upstream of the RBD. Furthermore, in this paper Qi et al (23) did not observe any interaction between Rab14 and the other class I FIPs.…”

“…However, more recently, a study by Goldenring, Spearman, and co-workers (23) reported that Rab14 does indeed bind to RCP, but via a region upstream of the RBD. Furthermore, in this paper Qi et al (23) did not observe any interaction between Rab14 and the other class I FIPs. They identified two serines (Ser-580 and Ser-582), which are not present in FIP2 and Rip11, that when mutated to asparagine and leucine, respectively, abolished the interaction with Rab14 without affecting the interaction with Rab11.…”