Cyclophilin A, dynein light chain 3, and HIV-1 capsid: Defining elements of host-pathogen interactions and roles in viral replication

HIV-1 capsid (CA) binds to cyclophilin A (CypA) and enhances viral replication via unknown mechanism(s). To gain insight into these mechanisms, we generated a series of CA mutants, measured binding affinity for CypA, and assessed effects on viral replication. An E98D mutant was unaffected for CypA binding and HIV-1 replication in all cell lines tested. E98Q and H87Q mutants exhibit a similar reduction in affinity for CypA. E98Q and the CypA-nonbinding mutant G89A/P90A (AA) were defective for replication in TZM-bl and CEM-GFP cells, but H87Q exhibited a replication advantage over wild-type (WT) in the same cells. Despite observed replication defects in CEM-GFP and TZM-bl, which exist at or before reverse transcription, E98Q and AA were fully competent for replication in Jurkat T cells. The observed cell-type specificity cannot be solely attributed to CypA expression and suggests that differential expression of other cellular factor(s), rather than defects in CypA binding, accounts for the observed phenotypes. Analysis of gene expression data enabled identification of differentially expressed candidate genes that may promote viral infectivity. One such gene, dynein light chain 3 (DYNLT3, also known as RP3), is overexpressed in CEM and TZM-bl cells relative to Jurkat cells. siRNA-mediated knockdown of RP3 in TZM-bl cells negatively affected HIV-1 replication of WT HIV-1, as well as all CA mutant HIV-1. We have demonstrated that CypA and RP3 cooperatively promote disassembly of oligomerized full-length WT CA. Thus, we have identified RP3 as a novel member of the CypA-HIV-1 CA complex, which, along with CypA, likely enhances viral replication in part by mediating uncoating of CA