Signal transduction by normal isoforms and W mutant variants of the Kit receptor tyrosine kinase.

摘要: Germline mutations at the Dominant White Spotting (W) and Steel (Sl) loci have provided conclusive genetic evidence that c-kit mediated signal transduction pathways are essential for normal mouse development. We analysed interactions of mutant W/c-kit gene products with cytoplasmic signalling proteins, using transient expression assays in COS cells. In addition to previously identified product (Kit+), a second Kit isoform (KitA+) containing an in-frame insertion, Gly-Asn-Asn-Lys, within extracellular domain, was detected murine mast cell cultures mid-gestation placenta. Both Kit+ KitA+ isoforms showed increased autophosphorylation enhanced association phosphatidylinositol (PI) 3' kinase PLC gamma 1, when stimulated recombinant soluble factor. No or increase phosphorylation GAP two GAP-associated p62 p190, observed. The had distinct activities absence exogenous factor; Kit+, but not KitA+, constitutive tyrosine accompanied by low level PI-3' 1. Introduction point substitutions associated W37 (Glu582----Lys) W41 (Val831----Met) alleles into constructs abolished (W37) reduced (W41) factor-induced receptor proteins manner proportional overall severity corresponding W phenotype. These data suggest diversity indicate phenotypes result from primary defects affect its interaction proteins.