Structural and Biochemical Characterization of the Catalytic Core of the Metastatic Factor P-Rex1 and Its Regulation by PtdIns(3,4,5)P3

• Published in: Structure (London) Vol. 24; no. 5; pp. 730 - 740
• Main Authors: Cash, Jennifer N., Davis, Ellen M., Tesmer, John J.G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 03-05-2016; Elsevier
• Subjects: BASIC BIOLOGICAL SCIENCES; Catalytic Domain; cdc42 GTP-Binding Protein - chemistry; cdc42 GTP-Binding Protein - metabolism; Guanine Nucleotide Exchange Factors - chemistry; Guanine Nucleotide Exchange Factors - metabolism; HEK293 Cells; Humans; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Molecular Docking Simulation; Molecular Dynamics Simulation; Phosphatidylinositol Phosphates - chemistry; Phosphatidylinositol Phosphates - metabolism; Protein Binding; rac1 GTP-Binding Protein - chemistry; rac1 GTP-Binding Protein - metabolism
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.02.022

Phosphatidylinositol 3,4,5-trisphosphate (PIP3)-dependent Rac exchanger 1 (P-Rex1) is a Rho guanine nucleotide exchange factor synergistically activated by PIP3 and Gβγ that plays an important role in the metastasis of breast, prostate, and skin cancer, making it an attractive therapeutic target. However, the molecular mechanisms behind P-Rex1 regulation are poorly understood. We determined structures of the P-Rex1 pleckstrin homology (PH) domain bound to the headgroup of PIP3 and resolved that PIP3 binding to the PH domain is required for P-Rex1 activity in cells but not for membrane localization, which points to an allosteric activation mechanism by PIP3. We also determined structures of the P-Rex1 tandem Dbl homology/PH domains in complexes with two of its substrate GTPases, Rac1 and Cdc42. Collectively, this study provides important molecular insights into P-Rex1 regulation and tools for targeting the PIP3-binding pocket of P-Rex1 with a new generation of cancer chemotherapeutic agents.
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•Structures of key enzymatic and regulatory domains of P-Rex1 were solved•Details of the PIP3 binding site are revealed at high resolution•PIP3 seems required for P-Rex1 activity but not membrane localization in cells•In vitro data support an allosteric mechanism for regulation of P-Rex1 by PIP3
Cash et al. report structures of P-Rex1 domains in complex with substrates or an analog of PIP3, an important regulator of P-Rex1 during cancer metastasis. The results suggest that PIP3 regulates P-Rex1 through an allosteric mechanism independent of membrane localization.