SHIP2 multiple functions: A balance between a negative control of PtdIns(3,4,5)P ₃ level, a positive control of PtdIns(3,4)P ₂ production, and intrinsic docking properties

<jats:title>Abstract</jats:title> <jats:p> The SH2 domain containing inositol 5‐phosphatase 2 (SHIP2) belongs to the family of the mammalian inositol polyphosphate 5‐phosphatases. The two closely related isoenzymes SHIP1 (or SHIP) and SHIP2 contain a N‐terminal SH2 domain, a catalytic domain, potential PTB domain‐binding sites (NPXY), and C‐terminal proline‐rich regions with consensus sites for SH3 domain interactions. In addition, SHIP2 contains a unique sterile alpha motif (SAM) domain that could be involved in SAM–SAM domain interactions with other proteins or receptors. SHIP2 also shows the presence of an ubiquitin interacting motif at the C‐terminal end. SHIP2 is essentially a PI(3,4,5)P <jats:sub>3</jats:sub> 5‐phosphatase that negatively controls PI(3,4,5)P <jats:sub>3</jats:sub> levels in intact cells and produce PI(3,4)P <jats:sub>2</jats:sub> . Depending on the cells and stimuli, PI(3,4)P <jats:sub>2</jats:sub> could accumulate at important levels and be a “second messenger” by its own. It could interact with a very large number of target proteins such as PKB or TAPP1 and 2 that control insulin sensitivity. In addition to its catalytic activity, SHIP2 is also a docking protein for a large number of proteins: Cytoskeletal, focal adhesion proteins, scaffold proteins, adaptors, protein phosphatases, and tyrosine kinase associated receptors. These interactions could play a role in the control of cell adhesion, migration, or endocytosis of some receptors. SHIP2 could be acting independently of its phosphatase activity being part of a protein network of some receptors, e.g., the EGF receptor or BCR/ABL. These non‐catalytic properties associated to a PI phosphatase have also been reported for other enzymes of the metabolism of myo‐inositol such as Ins(1,4,5)P <jats:sub>3</jats:sub> 3‐kinases, inositol phosphate multikinase (IPMK), or PTEN. J. Cell. Biochem. 112: 2203–2209, 2011. © 2011 Wiley‐Liss, Inc. </jats:p>