Discovery of Small Molecules That Target the Phosphatidylinositol (3,4,5) Trisphosphate (PIP3)-Dependent Rac Exchanger 1 (P-Rex1) PIP3-Binding Site and Inhibit P-Rex1–Dependent Functions in Neutrophils

• Published in: Molecular pharmacology Vol. 97; no. 3; pp. 226 - 236
• Main Authors: Cash, Jennifer N., Chandan, Naincy R., Hsu, Alan Y., Sharma, Prateek V., Deng, Qing, Smrcka, Alan V., Tesmer, John J.G.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD The American Society for Pharmacology and Experimental Therapeutics 01.03.2020
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.119.117556

Phosphatidylinositol (3,4,5) trisphosphate (PIP 3 )-dependent Rac exchanger 1 (P-Rex1) is a Rho guanine-nucleotide exchange factor that was originally discovered in neutrophils and is regulated by G protein βγ subunits and the lipid PIP 3 in response to chemoattractants. P-Rex1 has also become increasingly recognized for its role in promoting metastasis of breast cancer, prostate cancer, and melanoma. Recent structural, biochemical, and biologic work has shown that binding of PIP 3 to the pleckstrin homology (PH) domain of P-Rex1 is required for its activation in cells. Here, differential scanning fluorimetry was used in a medium-throughput screen to identify six small molecules that interact with the P-Rex1 PH domain and block binding of and activation by PIP 3 . Three of these compounds inhibit N-formylmethionyl-leucyl-phenylalanine induced spreading of human neutrophils as well as activation of the GTPase Rac2, both of which are downstream effects of P-Rex1 activity. Furthermore, one of these compounds reduces neutrophil velocity and inhibits neutrophil recruitment in response to inflammation in a zebrafish model. These results suggest that the PH domain of P-Rex1 is a tractable drug target and that these compounds might be useful for inhibiting P-Rex1 in other experimental contexts.