GRL-142 binds to and impairs HIV-1 integrase nuclear localization signal and potently suppresses highly INSTI-resistant HIV-1 variants.

Nuclear localization signal (NLS) of HIV-1 integrase (IN) is implicated in nuclear import of HIV-1 preintegration complex (PIC). Here, we established a multiclass drug-resistant HIV-1 variant (HIVKGD) by consecutively exposing an HIV-1 variant to various antiretroviral agents including IN strand transfer inhibitors (INSTIs). HIVKGD was extremely susceptible to a previously reported HIV-1 protease inhibitor, GRL-142, with IC50 of 130 femtomolar. When cells were exposed to HIVKGD IN-containing recombinant HIV in the presence of GRL-142, significant decrease of unintegrated 2-LTR circular cDNA was observed, suggesting that nuclear import of PIC was severely compromised by GRL-142. X-ray crystallographic analyses revealed that GRL-142 interacts with NLS's putative sequence (DQAEHLK) and sterically blocks the nuclear transport of GRL-142-bound HIVKGD's PIC. Highly INSTI-resistant HIV-1 variants isolated from heavily INSTI-experienced patients proved to be susceptible to GRL-142, suggesting that NLS-targeting agents would serve as salvage therapy agents for highly INSTI-resistant variant-harboring individuals. The data should offer a new modality to block HIV-1 infectivity and replication and shed light on developing NLS inhibitors for AIDS therapy.

Serine hydroxymethyltransferase as a potential target of antibacterial agents acting synergistically with one-carbon metabolism-related inhibitors.

Serine hydroxymethyltransferase (SHMT) produces 5,10-methylenetetrahydrofolate (CH2-THF) from tetrahydrofolate with serine to glycine conversion. SHMT is a potential drug target in parasites, viruses and cancer. (+)-SHIN-1 was developed as a human SHMT inhibitor for cancer therapy. However, the potential of SHMT as an antibacterial target is unknown. Here, we show that (+)-SHIN-1 bacteriostatically inhibits the growth of Enterococcus faecium at a 50% effective concentration of 10-11 M and synergistically enhances the antibacterial activities of several nucleoside analogues. Our results, including crystal structure analysis, indicate that (+)-SHIN-1 binds tightly to E. faecium SHMT (efmSHMT). Two variable loops in SHMT are crucial for inhibitor binding, and serine binding to efmSHMT enhances the affinity of (+)-SHIN-1 by stabilising the loop structure of efmSHMT. The findings highlight the potency of SHMT as an antibacterial target and the possibility of developing SHMT inhibitors for treating bacterial, viral and parasitic infections and cancer.