HIV-1 Nef CAWLEAQ motif: a regulator of monocytes invasion through ENO1 modulation

HIV-1 transmission and spread involves significant host-virus interaction. Possible targets for obstacle of HIV-1 lie at the site of mucosal barriers. Thus a better understanding of how HIV-1 infects target cells at such sites and leads their invasion is required, with prime focus on the host determinants regulating HIV-1 spread. For the viral infectivity and pathogenicity, HIV-1 Nef facilitates immune evasion through protein-protein interactions within host cell. HIV-1 Nef is significant for viral infectivity and pathogenicity. It enhances HIV-1 replication, facilitating immune evasion by interacting with various host factors and altering cellular pathways via multiple protein-protein interactions. In this study, HIV-1 Nef forms with specific mutations, revealing sequence variability, were studied for their effects in human SupT1 T cell line and (THP-1) monocyte-macrophage cell line. Proteins being downregulated by Nef in SupT1 were further observed in THP-1, and interestingly two host proteins' (ENO-1 and VDAC1) expression was found to be cell lineage specific, being stimulatory in macrophages/monocytes and inhibitory in T cells. Cell migration, invasion and ADP release studies were employed to determine the biological function affected by Nef-mediated regulation of these two host proteins. ENO1-regulated function: cell invasion was enhanced in THP-1 cells, but was inhibited in SupT1 cells by Nef RP01. In addition, the modulation of proteins and cell invasion remained unaffected by a Nef RP14. These results indicated that regulation of host protein expression and invasive property of host cells by Nef was sequence specific, suggesting involvement of a particular motif of Nef. To precisely determine this site, we designed a heptapeptide including the CAWLEAQ-regulating sequence of Nef. Macrophages/monocytes being the major cells affected by HIV-1 at mucosal barriers were particularly investigated by the peptide. The peptide led to reversal of differential expressions of ENO1 in both SupT1 and THP-1 and inhibition of enhanced invasiveness in THP-1 cells. Further AP-1 was identified as a factor involved in this Nef-mediated regulation of host proteins. Together these findings suggest a possible mechanism of host invasion by HIV-1 through the CAWLEAQ motif of Nef-mediated regulation of ENO1 and identify a potential therapeutic target for HIV-1 entry at mucosal barriers.