The C domain of HIV-1 gp41 binds the putative cellular receptor protein P62

Objective: To characterize the binding of gp41 with the putative receptor protein P62. Design: HIV-1 gp41 binds several cellular proteins by two binding sites, one of which has been shown to bind to a putative receptor protein P45 (45 kDa). Based on this, an attempt was made to determine the relationship between the two binding sites and P62 (62 kDa). Methods: Using surface plasmon resonance (SPR) measurement, the interaction was measured between recombinant soluble gp41 (rsgp41, Env aa539-684) and protein P62. Inhibition of this interaction was attempted by the use of synthetic peptides (P1, aa583-599; P2, aa646-674) corresponding to the two binding sites in gp41. In addition, the direct binding of P62 to peptide P2 was examined in an enzyme-linked immunosorbent assay. Results: Using SPR measurement, the interaction between P62 and rsgp41 confirmed, and the interaction was found to be inhibited by only the synthetic peptide P2 sequence that corresponds to the C domain of gp41; neither P1 nor a control peptide inhibited the interaction. Moreover, like rsgp41, P2 was able to bind P62 whereas P1 and another recombinant gp41 (aa567-648 that does not include the C domain) were not. Conclusions: P62 bound rsgp41 and the synthetic peptide P2. This interaction could be inhibited only by P2. These results indicate that the C domain of HIV-1 gp41 binds P62.