Src family kinases are involved in the differential signaling from two splice forms of c-Kit.
In both mice and humans alternate splicing results in isoforms of c-Kit characterized by the presence or the absence of a tetrapeptide sequence, GNNK, in the juxtamembrane region of the extracellular domain. Dramatic differences in the kinetics and magnitude of activation of the intrinsic tyrosine kinase activity of c-Kit between the GNNK- and GNNK+ isoforms has previously been shown. Here we report the analysis of downstream targets of receptor signaling, which revealed that the signaling was differentially regulated in the two splice forms. The kinetics of phosphorylation of Shc, previously demonstrated to be phosphorylated by Src downstream of c-Kit, was stronger and more rapid in the GNNK- form, whereas it showed slower kinetics in the GNNK+ form. Inhibition of Src family kinases with the specific Src family kinase inhibitor SU6656 altered the kinetics of activation of the GNNK- form of c-Kit so that it resembled that of the GNNK+ form. In cells expressing the GNNK- form, SCF was rapidly degraded, whereas in cells expressing the GNNK+ form only showed a very slow rate of degradation of SCF. In the GNNK+ form the Src inhibitor SU6656 only had a weak effect on degradation, whereas in the GNNK- form it dramatically inhibited degradation. In summary, the two splice forms show, despite only a four-amino acid sequence difference, remarkable differences in their signaling capabilities.
Voytyuk
Olexandr
O
Ludwig Institute for Cancer Research, Biomedical Center, SE-751 24 Uppsala, Sweden, Sweden.
Lennartsson
Johan
J
Mogi
Akira
A
Caruana
Georgina
G
Courtneidge
Sara
S
Ashman
Leonie K
LK
Rönnstrand
Lars
L
D016475:3T3 Cells; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology*
D007211:Indoles; D008024:Ligands; D020033:Protein Isoforms; D011994:Recombinant Proteins; C416927:SU 6656; D013449:Sulfonamides; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D019061:src-Family Kinases