INPP4b (D9K1B) XP^® Rabbit mAb #14543

Phosphatidylinositol lipids and phosphoinositides are important second messengers, their generation controlling many cellular events. Intracellular levels of these molecules are regulated by phosphoinositide kinases and phosphatases. One of the best characterized lipid kinases is phosphoinositide 3-kinase (PI3K), which is responsible for phosphorylation on the D-3 position of the inositide head group (1). This action of PI3K catalyzes the production of phosphatidylinositol-3,4,5-triphosphate by phosphorylating phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), and phosphatidylinositol-4,5-bisphosphate (PIP2). Growth factors and hormones trigger this phosphorylation event, which in turn coordinates cell growth, cell cycle entry, cell migration, and cell survival (1). PTEN, the well characterized partnering phosphatase, reverses this process by removing the phosphate from PI(3,4,5)P3 at the D-3 position to generate PI(4,5)P2 (1,2). Dephosphorylation on the D-5 position to generate PI(3,4)P2 occurs through the action of SHIP1 or SHIP2 (3), and dephosphorylation on the D-4 position to generate PI(3)P can occur through the action of inositol polyphosphate 4-phosphatase isoenzymes type I (INPP4a) and type II (INPP4b) (4,5). While INPP4a has been implicated in neuronal survival and megakaryocyte lineage determination (6,7), less is understood about INPP4b. It has been shown that two splice variants of INPP4b occur in mice, each showing distinct tissue distribution and subcellular localization (5,8).