title: Constitutively active Galpha16 stimulates STAT3 via a c-Src/JAK- and ERK-dependent mechanism.
abstract: The hematopoietic-specific Galpha16 protein has recently been shown to mediate receptor-induced activation of the signal transducer and activator of transcription 3 (STAT3). In the present study, we have delineated the mechanism by which Galpha16 stimulates STAT3 in human embryonic kidney 293 cells. A constitutively active Galpha16 mutant, Galpha16QL, stimulated STAT3-dependent luciferase activity as well as the phosphorylation of STAT3 at both Tyr705 and Ser727. Galpha16QL-induced STAT3 activation was enhanced by overexpression of extracellular signal-regulated kinase 1 (ERK1), but was inhibited by U0126, a Raf-1 inhibitor, and coexpression of the dominant negative mutants of Ras and Rac1. Inhibition of phospholipase Cbeta, protein kinase C, and calmodulin-dependent kinase II by their respective inhibitors also suppressed Galpha16QL-induced STAT3 activation. The involvement of tyrosine kinases such as c-Src and Janus kinase 2 and 3 (JAK2 and JAK3) in Galpha16QL-induced activation of STAT3 was illustrated by the combined use of selective inhibitors and dominant negative mutants. In contrast, c-Jun N-terminal kinase, p38 MAPK, RhoA, Cdc42, phosphatidylinositol 3-kinase, and the epidermal growth factor receptor did not appear to be required. Similar observations were obtained with human erythroleukemia cells, where STAT3 phosphorylation was stimulated by C5a in a PTX-insensitive manner. Collectively, these results highlight the important regulatory roles of the Ras/Raf/MEK/ERK and c-Src/JAK pathways on the stimulation of STAT3 by activated Galpha16. Demonstration of the involvement of different kinases in Galpha16QL-induced STAT3 activation supports the involvement of multiple signaling pathways in the regulation of transcription by G proteins.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Rico K H
authors.initials: RK
authors.lastname: Lo
authors.forename: Helen
authors.initials: H
authors.lastname: Cheung
authors.forename: Yung H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D015936:Complement C5a / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D005799:Genes, Dominant; D017930:Genes, Reporter; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D054799:Phospholipase C beta; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D050796:STAT3 Transcription Factor; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D002070:Butadienes; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009570:Nitriles; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; C113580:U 0126; D014443:Tyrosine; D012694:Serine; D015936:Complement C5a; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C112631:G protein alpha 16; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein