We show that in DT 40 chicken B cell lines , antibody stimulation leads to PI3K dependent tyrosine phosphorylation of DAPP 1 that is lost in Lyn or Syk deficient cell lines but not Btk deficient cell lines . ^^^ Finally , in vitro we find lipid modified Src to be the most effective DAPP 1 tyrosine kinase ( versus Syk , Lyn , Btk , and Bmx ) ; phosphorylation of DAPP 1 but not Src autophosphorylation is stimulated approximately 10 fold by PtdIns ( 3 , 4 , 5 ) P ( 3 ) ( IC ( 50 ) = 150 nm ) and phosphatidylinositol 3 , 4 bisphosphate but not by their nonbiological diastereoisomers and depends on PH domain mediated binding of DAPP 1 to PtdIns ( 3 , 4 , 5 ) P ( 3 ) containing membranes . ^^^ |