Autoregulation of Class II Alpha PI3K Activity by Its Lipid-Binding PX-C2 Domain Module

Mol Cell. 2018 Jul 19;71(2):343-351.e4. doi: 10.1016/j.molcel.2018.06.042.


Class II phosphoinositide 3-kinases (PI3K-C2) are large multidomain enzymes that control cellular functions ranging from membrane dynamics to cell signaling via synthesis of 3'-phosphorylated phosphoinositides. Activity of the alpha isoform (PI3K-C2α) is associated with endocytosis, angiogenesis, and glucose metabolism. How PI3K-C2α activity is controlled at sites of endocytosis remains largely enigmatic. Here we show that the lipid-binding PX-C2 module unique to class II PI3Ks autoinhibits kinase activity in solution but is essential for full enzymatic activity at PtdIns(4,5)P2-rich membranes. Using HDX-MS, we show that the PX-C2 module folds back onto the kinase domain, inhibiting its basal activity. Destabilization of this intramolecular contact increases PI3K-C2α activity in vitro and in cells, leading to accumulation of its lipid product, increased recruitment of the endocytic effector SNX9, and facilitated endocytosis. Our studies uncover a regulatory mechanism in which coincident binding of phosphoinositide substrate and cofactor selectively activate PI3K-C2α at sites of endocytosis.

Keywords: clathrin; endocytosis; hydrogen-deuterium exchange mass spectrometry; lipid-binding domain; phosphatidylinositol 3,4-bisphosphate; phosphatidylinositol 3-kinase C2alpha; phosphoinositides; sorting nexin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • C2 Domains / physiology
  • COS Cells
  • Chlorocebus aethiops
  • Class I Phosphatidylinositol 3-Kinases / metabolism
  • Class I Phosphatidylinositol 3-Kinases / physiology
  • Class II Phosphatidylinositol 3-Kinases / metabolism*
  • Class II Phosphatidylinositol 3-Kinases / physiology*
  • Clathrin / physiology
  • Endocytosis / physiology
  • HEK293 Cells
  • Homeostasis
  • Humans
  • Lipids / physiology
  • Mass Spectrometry
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphorylation
  • Protein Binding
  • Protein Domains
  • Signal Transduction


  • Clathrin
  • Lipids
  • Class I Phosphatidylinositol 3-Kinases
  • Class II Phosphatidylinositol 3-Kinases
  • PIK3CA protein, human