title: C-KIT signaling depends on microphthalmia-associated transcription factor for effects on cell proliferation.
abstract: The development of melanocytes is regulated by the tyrosine kinase receptor c-KIT and the basic-helix-loop-helix-leucine zipper transcription factor Mitf. These essential melanocyte survival regulators are also well known oncogenic factors in malignant melanoma. Despite their importance, not much is known about the regulatory mechanisms and signaling pathways involved. In this study, we therefore sought to identify the signaling pathways and mechanisms involved in c-KIT mediated regulation of Mitf. We report that c-KIT stimulation leads to the activation of Mitf specifically through the c-KIT phosphorylation sites Y721 (PI3 kinase binding site), Y568 and Y570 (Src binding site). Our study not only confirms the involvement of Ras-Erk signaling pathway in the activation of Mitf, but also establishes that Src kinase binding to Y568 and Y570 of c-KIT is required. Using specific inhibitors we observe and verify that c-KIT induced activation of Mitf is dependent on PI3-, Akt-, Src-, p38- or Mek kinases. Moreover, the proliferative effect of c-KIT is dependent on Mitf in HEK293T cells. In contrast, c-KIT Y568F and Y721F mutants are less effective in driving cell proliferation, compared to wild type c-KIT. Our results reveal novel mechanisms by which c-KIT signaling regulates Mitf, with implications for understanding both melanocyte development and melanoma.
authors: Wallenberg Laboratory, Experimental Clinical Chemistry, Department of Laboratory Medicine, Lund University, Skåne University Hospital, Malmö, Sweden. bengt.phung@med.lu.se
authors: Bengt
authors: B
authors: Phung
authors: Jianmin
authors: J
authors: Sun
authors: Alexander
authors: A
authors: Schepsky
authors: Eirikur
authors: E
authors: Steingrimsson
authors: Lars
authors: L
authors: Rönnstrand
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D006801:Humans; D008544:Melanocytes / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D051739:Microphthalmia-Associated Transcription Factor / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020125:Mutation, Missense; D010766:Phosphorylation; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D019009:Proto-Oncogene Proteins c-kit; D020929:Mitogen-Activated Protein Kinase Kinases