title: A novel MPL point mutation resulting in thrombopoietin-independent activation.
abstract: Thrombopoietin (TPO) and its receptor (MPL) are important regulators of megakaryopoiesis. MPL belongs to a cytokine receptor superfamily. To date, all constitutively active MPL mutants have been artificially constructed with amino acid substitutions in the transmembrane domain or extracellular domain of the protein, and they activate signal transduction pathways in Ba/F3 cells that can also be activated by the normal MPL. In this paper, we report a novel spontaneously occurring mutation of MPL, with an amino acid substitution of Trp(508) to Ser(508) in the intracellular domain of MPL, that induces the factor-independent growth of Ba/F3 cells. Examination of intracellular signaling pathways demonstrated that the mutant MPL protein constitutively activates three distinct signaling pathways, SHC-Ras-Raf-MAPK/JNK, JAK-STAT, and PI3K-Akt-Bad.
authors.affiliation: Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co Ltd, Tsukuba, Ibaraki, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Abe
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: O
authors.initials: O
authors.lastname: Inagaki
authors.forename: S
authors.initials: S
authors.lastname: Sassa
authors.forename: H
authors.initials: H
authors.lastname: Shikama
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D019943:Amino Acid Substitution; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D053614:Janus Kinase 2; D020935:MAP Kinase Signaling System; D051379:Mice; D008807:Mice, Inbred BALB C; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020125:Mutation, Missense; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction / Q000502:physiology*; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013329:Structure-Activity Relationship; D013926:Thrombopoietin / Q000494:pharmacology*; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D051025:bcl-Associated Death Protein; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D053614:Janus Kinase 2; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011993:Recombinant Fusion Proteins; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013926:Thrombopoietin; D015534:Trans-Activators; D051025:bcl-Associated Death Protein; D020703:ras GTPase-Activating Proteins; C494819:BAD protein, human; C494820:Bad protein, mouse; C528024:SHC1 protein, human; C494086:STAT3 protein, human; C528034:Shc1 protein, mouse; C494087:Stat3 protein, mouse; C082218:MPL protein, human; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; C494918:AKT1 protein, human