The Steel/W transduction pathway: kit autophosphorylation and its association with a unique subset of cytoplasmic signaling proteins is induced by the Steel factor.

Abstract

The Wlc-kit and Steel loci respectively encode a receptor tyrosine kinase (Kit) and its extracellular ligand, Steel factor, which are essential for the development of hematopoietic, melanocyte, and germ cell lineages in the mouse. To determine the biochemical basis of the SteeliW developmental pathway, we have investigated the response of the Kit tyrosine kinase and several potential cytoplasmic targets to stimulation with Steel in mast cells derived from normal and mutant W mice. In normal mast cells, Steel induces Kit to autophosphorylate on tyrosine and bind to phosphatidylinositol 3'-kinase (P13K) and phospholipase C-yl but not detectably to Ras GTPase-activating protein. Additionally, we present evidence that Kit tyrosine phosphorylation acts as a switch to promote complex formation with P13K. In mast cells from mice homozygous for the W42 mutant allele, Kit is not tyrosine phosphorylated and fails to bind PI3K following Steel stimulation. In contrast, in the transformed mast cell line P815, Kit is constitutively phosphorylated and binds to P13K in the absence of ligand. These results suggest that Kit autophosphorylation and its physical association with a unique subset of cytoplasmic signaling proteins are critical for mammalian development.

Isoforms of c-KIT differ in activation of signalling pathways and transformation of NIH3T3 fibroblasts

“…The data presented here imply major di erences between the isoforms in their interaction with signal transducing molecules. It will be important to investigate their interactions with phosphatases such as SHP-1 which is associated with c- KIT (Yi and Ihle, 1993) and a range of proteins such as Shc (Matsuguchi et al, 1994), Tec (Tang et al, 1994), Lyn , PLCg1 (Rottapel et al, 1991;Herbst et al, 1995b), p120 CBL (Wisniewski et al, 1996), JAK2 (Weiler et al, 1996) and Stat 1 that are known to be recruited or activated on SLF binding to c-KIT.…”

Tyrosine Phosphorylation of the Related Adhesion Focal Tyrosine Kinase in Megakaryocytes upon Stem Cell Factor and Phorbol Myristate Acetate Stimulation and Its Association with Paxillin

“…SCF treatment is known to increase cytoplasmic calcium levels (34) and to stimulate the phosphorylation of the components of c-KIT-associated signaling pathways (35,36). Since SCF effects are modulated by PKC (30,37), the role of PKC in RAFTK stimulation was investigated.…”

Specific and common activities of the FLT3 and KIT tyrosine kinase receptors revealed by the use of cultured mast cells

“…Cytoplasmic proteins involved in mitogenic pathways have been largely described for KIT, FMS and FLT3, [30][31][32][33][34]60,61 although few of them were reported to be involved in a pathway common to all three RTK. Mutated receptors, deficient in different substrate binding sites, will be useful in the description of such pathways.…”

“…Both KIT and PDGF␤-R are associated with PLC␥ and PI3Ј kinase, whereas FLT3 shows an association with PI3Ј kinase only. [30][31][32][33]63,64 In this study, we showed that FLT3 is unable to promote adhesion of mast cells to a fibronectin matrix. It is not known whether this results from either the lack of PLC␥ activity or from the different location, at the C-terminus sequence of the SH2-p85-PI3Ј kinase binding site (Tyr 958) of FLT3 64 compared to other class III RTK.…”

“…One direction that we and others have explored, is to determine the nature and the corresponding functions of the cytoplasmic transduction pathways activated in response to FL or KL. [30][31][32][33][34] Coexpression of both receptors into the same hematopoietic cell population could help us to analyze the possible crosstalk between the two transduction pathways. To this purpose, we expressed a chimeric receptor, FF3, composed of the FMS/CSF1R ligand binding ectodomain fused to the transmembrane and cytoplasmic domains of mFLT3, 35 in mast cell populations derived from fetal liver and bone marrow, from W/W, as well as wild-type mice.…”