Identification of a second SH2-domain-containing protein closely related to the phosphatidylinositol polyphosphate 5-phosphatase SHIP.

Distinct inositol and phosphatidylinositol polyphosphates 5-phosphatases have recently been cloned. Primers have been designed coding for highly conserved amino acid regions that are shared between sequences of 5-phosphatases. One of the PCR fragment referred to as 51 C, shows 99% identity to a previously reported sequence (INPPL-1) present in the database. We report here the identification of cDNAs for a new SH2-domain-containing protein showing homology to the inositol 5-phosphatase SHIP and therefore referred to as SHIP2. SHIP2 differs at both N- and C-terminal ends with the sequence of INPPL-1. The translated sequence of SHIP2 encodes a 1258 amino acid protein with a predicted molecular mass of 142 kDa. Particularly high levels of SHIP2 were found in human heart, skeletal muscle and placenta as shown by Northern blot analysis. SHIP2 was also expressed in dog thyroid cells in primary culture where the expression was enhanced in TSH and EGF-stimulated cells.