This entry includes INPP4A and INPP4B. They are inositol lipid 4-phosphatases that hydrolyze PtdIns(3,4)P2, a phosphoinositide generated by PI3K signaling [, ]. They contain a C2 domain in their N termini and a phosphatase domain at their C termini. INPP4A is a suppressor of glutamate excitotoxicity in the central nervous system [], while INPP4B acts as a tumour suppressor [].