title: Transcriptional activation of c-Fos by constitutively active Galpha(16)QL through a STAT1-dependent pathway.
abstract: Hematopoietic restrictive Galpha(16) has long been known to stimulate phospholipase Cbeta (PLCbeta) and induce mitogen-activated protein kinase (MAPK) phosphorylation. Recently, we have demonstrated that Galpha(16) is capable of inducing the phosphorylation and transcriptional activation of transcription factors, such as signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappaB (NFkappaB). However, the downstream signaling regulation by Galpha(16) has not yet been documented. In the present study, we have determined the signaling mechanism by which constitutively active Galpha(16) mediates c-Fos transcriptional activation in human embryonic kidney (HEK) 293 cells. Overexpression of constitutively active Galpha(16), Galpha(16)QL, resulted in the stimulation of c-Fos transcriptional activation in HEK 293 cells. The participation of PLCbeta, c-Src/Janus kinase 2 (JAK2) and extracellular signal-regulated kinase (ERK) signaling pathways in Galpha(16)QL-induced c-Fos transcriptional activation was demonstrated by the use of their specific inhibitors. However, c-Jun N terminal kinase (JNK), p38 MAPK and phosphatidylinositol-3 kinase (PI3K) were not required. Interestingly, the dominant negative mutant of STAT1, but not STAT3, suppressed c-Fos transcriptional activation induced by Galpha(16)QL, implying that STAT1 was involved in this signaling mechanism. To further examine the role of STAT1 in the signaling pathway of Galpha(16), we demonstrated that Galpha(16)QL was able to induce STAT1 activation. Also, stimulation of adenosine A1 receptor-coupled Galpha(16) was shown to induce ERK and STAT1 phosphorylations in a concentration-dependent manner. Using selective inhibitors, PLCbeta, c-Src/JAK and ERK, but not JNK, p38 MAPK and PI3K, were shown to be involved in Galpha(16)QL-induced STAT1 activation. Collectively, our results demonstrate for the first time that stimulation of Galpha(16) can lead to STAT1-dependent c-Fos transcriptional activation via PLCbeta, c-Src/JAK and ERK pathways.
authors.affiliation: Department of Biochemistry, Molecular Neuroscience Center, and Biotechnology Research Institute, 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: Yung H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058907:Adenosine A1 Receptor Agonists; D015153:Blotting, Western; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D054799:Phospholipase C beta; D010766:Phosphorylation / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D043682:Receptor, Adenosine A1 / Q000235:genetics / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015533:Transcriptional Activation; D014162:Transfection; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000241:Adenosine; D058907:Adenosine A1 Receptor Agonists; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D044385:GTP-Binding Protein alpha Subunits; D007527:Isoenzymes; D048031:JNK Mitogen-Activated Protein Kinases; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D054799:Phospholipase C beta; D016760:Proto-Oncogene Proteins c-fos; D016392:Proto-Oncogene Proteins pp60(c-src); D043682:Receptor, Adenosine A1; D050794:STAT1 Transcription Factor; D010738:Type C Phospholipases; D048051:p38 Mitogen-Activated Protein Kinases; C027513:N(6)-cyclohexyladenosine