title: Early myeloid cells expressing c-KIT isoforms differ in signal transduction, survival and chemotactic responses to Stem Cell Factor.
abstract: Isoforms of the receptor tyrosine kinase, c-KIT, differ in the presence or absence of a GNNK tetrapeptide in the extracellular juxtamembrane region. When expressed in murine NIH3T3 cells, these isoforms of c-KIT showed differential activation of signaling pathways and proliferation in response to Stem Cell Factor (SCF). However, c-KIT is not normally expressed by fibroblasts, but plays a key role in hematopoiesis. Because signaling pathways and cellular responses mediated by c-KIT differ in different cell types, we studied the effects of SCF stimulation on factor-dependent murine early myeloid cells expressing human GNNK+ or GNNK- c-KIT. As in fibroblasts, SCF activation of the GNNK- isoform resulted in stronger, more rapid receptor phosphorylation, and activation of Src kinases, while only a minor effect on the phosphatidylinositol 3-kinase pathway was observed. Similarly, more rapid Src kinase-dependent internalisation of the GNNK- isoform occurred in response to SCF. In contrast to fibroblasts, only minor differences in ERK activation were seen indicating that early hematopoietic cells, unlike fibroblasts, are not dependent on Src kinases for activation of this pathway in response to SCF. Enhanced SCF-dependent growth was observed in GNNK- c-KIT expressing cells due to lower cell attrition. The rate of cell division was similar. Importantly, cells expressing the GNNK- isoform showed a greater chemotactic response to SCF.
authors.affiliation: School of Biomedical Sciences, University of Newcastle, University Drive, Callaghan NSW 2308, and Hunter Medical Research Institute, Newcastle, Australia.
authors.forename: Sonia M
authors.initials: SM
authors.lastname: Young
authors.forename: Antony C
authors.initials: AC
authors.lastname: Cambareri
authors.forename: Adam
authors.initials: A
authors.lastname: Odell
authors.forename: Sean M
authors.initials: SM
authors.lastname: Geary
authors.forename: Leonie K
authors.initials: LK
authors.lastname: Ashman
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D002633:Chemotaxis; D004705:Endocytosis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D051379:Mice; D022423:Myeloid Cells / Q000201:enzymology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D019089:Stem Cell Factor; D019869:Phosphatidylinositol 3-Kinases; D019009:Proto-Oncogene Proteins c-kit; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases