MYELOID NEOPLASIA Lyn- and PLC- 3–dependent regulation of SHP-1 phosphorylation controls Stat5 activity and myelomonocytic leukemia-like disease

Hyperactivation of the transcription factor Stat5 leads to various leukemias. Stat5 activity is regulated by the protein phosphatase SHP-1 in a phospholipase C (PLC)– 3-dependent manner. Thus, PLC3–deficient mice develop myeloproliferative neoplasm, like Lyn (Src family kinase)– deficient mice. Here we show that Lyn/ PLC3 doubly deficient lyn / ;PLC3 / mice develop a Stat5-dependent, fatal myelodysplastic/myeloproliferative neoplasm, similar to human chronic myelomonocytic leukemia (CMML). In hematopoietic stem cells of lyn / ;PLC3 / mice that cause the CMML-like disease, phosphorylation of SHP-1 at Tyr536 and Tyr564 is abrogated, resulting in reduced phosphatase activity and constitutive activation of Stat5. Furthermore, SHP-1 phosphorylation at Tyr564 by Lyn is indispensable for maximal phosphatase activity and for suppression of the CMMLlike disease in these mice. On the other hand, Tyr536 in SHP-1 can be phosphorylated by Lyn and another kinase(s) and is necessary for efficient interaction with Stat5. Therefore, we identify a novel Lyn/ PLC3–mediated regulatory mechanism of SHP-1 and Stat5 activities. (Blood. 2010; 116(26):6003-6013)