Sergei Nekhai

Center for Sickle Cell Disease, USA

Title: Protein phosphatase-1 as a target for antiviral small molecules against HIV-1 infections


Sergei Nekhai has a Ph.D. degree in biophysics from St. Petersburg Nuclear Physics Institute, Russia. He did his postdoctoral training at the George Washington University. He serves as co-Director for Howard University’s Center for Sickle Cell Disease and Director of Proteomics. He studies HIV-1 transcription, pulmonary hypertension in sickle cell disease and iron metabolism with the focus on ferroportin mutations that might pose a risk for iron overload and worsen HIV-1 infection in African-Americans. He has more than 50 publications in basic virology and hematology journals and serves as a PI and co-PI on several NIH-funded grants.


HIV-1 transcription is activated by Tat protein that recruits CDK9/cyclin T1 to TAR RNA. We previously showed that Tat also binds to protein phosphatase-1 (PP1) through the Q35VCF38 sequence and translocates PP1 to the nucleus. PP1 dephosphorylates CDK9 and activates HIV-1 transcription. We recently identified PP1-targeting small molecule, 1H4, that prevented HIV-1 Tat interaction with PP1 and inhibited HIV-1 gene transcription. Using the model of 1H4-PP1 complex we iteratively designed and synthesized follow-up libraries that were analyzed for the inhibition of HIV-1 transcription and toxicity. We obtained a tetrahydroquinoline derivative, 1E7, which inhibited phosphatase activity of PP1 and also disrupted the interaction of Tat with PP1. We further optimized 1E7 and obtained compound 1E7-03 that inhibited HIV-1 with low IC50, showed no toxicity when administered in mice. The 1E7-03 was also active in HIV-1 transgenic mice preventing death from acute lung inflammation induced by LPS injection. The LPS administration led to neutrophil and macrophages recruitment to the lungs where HIV-1 expression in the lung macrophages prevented neutrophil clearance. Injection of 1E7-03 reduced both macrophages and neutrophil accumulation in the lungs likely due to the reduction of HIV-1 expression. We further analyzed stability of 1E7-03 compound and identified its major metabolites. We also developed 1E7-03 analogs that had improved stability and showed similar activity to the parental compound. Our study shows that PP1 can serve as a target for development of novel therapeutics against HIV-1 to target HIV-1 expression in lungs and potentially other organs. Acknowledgements: This work was supported by NIH Research Grants (1P50HL118006, 1R01HL125005, U19AI109664 and 5G12MD007597), and District of Columbia Developmental Center for AIDS Research grant (P30AI087714). This study was also funded in part with NIH Grant UL1TR000101 from the National Center for Advancing Translational Sciences (NCATS), National Institutes of Health (NIH), through the Clinical and Translational Science Awards Program (CTSA), a trademark of DHHS, part of the Roadmap Initiative, “Re-Engineering the Clinical Research Enterprise.” The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.