Targeting phosphoinositide 3-kinase (PI3K) in head and neck squamous cell carcinoma (HNSCC)

Linear composition of p110α and p85α molecules. Red arrowheads in p110α indicate ‘hotspot’ mutations. C2 in p110α is a putative membrane-binding domain. Breakpoint cluster region-homology (BH) domain in p85α has shown GTPase activating protein (GAP) activity toward Rab family. Rab GTPase induces degradation and deregulation of activated growth factor receptors, and mutated Rab GAP induces cell transformation [148]. However, it is unclear if this function is still active in complex with p110α [149]. BH domain in p85α is flanked by proline-rich domain, implying an auto-regulatory mechanism in interaction with its SH3 domain [150