Distinct regions of c-Mpl cytoplasmic domain are coupled to the JAK-STAT signal transduction pathway and Shc phosphorylation.
c-Mpl, a member of the hematopoietic cytokine receptor family, is the receptor for thrombopoietin. To investigate signal transduction by c-Mpl, a chimeric receptor, composed of the extracellular domain of human growth hormone receptor and the intracellular domain of c-Mpl, was introduced into the interleukin 3-dependent cell line Ba/F3. In response to growth hormone, this chimeric receptor induced growth in the absence of interleukin 3. Deletion analysis of the 123-amino acid intracellular domain indicated that the elements responsible for this effect are present within the 63 amino acids proximal to the transmembrane domain. Mutation of the recently described box 1 motif abrogated the proliferative response. Tyrosine phosphorylation of the tyrosine kinase JAK-2 and activation of STAT proteins were dependent on box 1 and sequences within 63 amino acids of the plasma membrane. STAT proteins activated by thrombopoietin in a megakaryocytic cell line were purified and shown to be STAT1 and STAT3. A separate region located at the C terminus of the c-Mpl intracellular domain was found to be required for induction of Shc phosphorylation and c-fos mRNA accumulation, suggesting involvement of the Ras signal transduction pathway. Thus, at least two distinct regions are involved in signal transduction by the c-Mpl.
Gurney
A L
AL
Department of Molecular Biology, Genetech, Inc., South San Francisco, CA 94080, USA.
Wong
S C
SC
Henzel
W J
WJ
de Sauvage
F J
FJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D009838:Oligodeoxyribonucleotides; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D018121:Receptors, Cytokine / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism; D053628:Receptors, Thrombopoietin; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009838:Oligodeoxyribonucleotides; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D011971:Receptors, Immunologic; D053628:Receptors, Thrombopoietin; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; C082218:MPL protein, human; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D018631:ras Proteins