PMID: 30293811

Authors:

Chen KE, Tillu VA, Chandra M, Collins BM

Title:

Molecular Basis for Membrane Recruitment by the PX and C2 Domains of Class II Phosphoinositide 3-Kinase-C2alpha.

Journal:

Structure. 2018 Sep 19. pii: S0969-2126(18)30298-3. doi:, 10.1016/j.str.2018.08.010.

Abstract:

Phosphorylation of phosphoinositides by the class II phosphatidylinositol 3-kinase (PI3K) PI3K-C2alpha is essential for many processes, including neuroexocytosis and formation of clathrin-coated vesicles. A defining feature of the class II PI3Ks is a C-terminal module composed of phox-homology (PX) and C2 membrane interacting domains; however, the mechanisms that control their specific cellular localization remain poorly understood. Here we report the crystal structure of the C2 domain of PI3K-C2alpha in complex with the phosphoinositide head-group mimic inositol hexaphosphate, revealing two distinct pockets for membrane binding. The C2 domain preferentially binds to phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate, and low-resolution structures of the combined PX-C2 module by small-angle X-ray scattering reveal a compact conformation in which cooperative lipid binding by each domain binding can occur. Finally, we demonstrate an unexpected role for calcium in perturbing the membrane interactions of the PX-C2 module, which we speculate may be important for regulating the activity of PI3K-C2alpha.