Activation of nuclear factor {kappa}B by somatostatin type 2 receptor in pancreatic acinar AR42J cells involves G{alpha}14 and multiple signaling components: a mechanism requiring protein kinase C, calmodulin-dependent kinase II, ERK, and c-Src.
Medications targeting the somatostatin type 2 receptor (SSTR2) have been employed for pancreatic inflammations and cancers, possibly via the regulation of the transcription factor nuclear factor kappaB (NFkappaB). Here we demonstrate that in tumoral pancreatic acinar AR42J cells, activation of SSTR2 leads to stimulation of the inhibitor kappaB kinase (IKK)/NFkappaB signaling cascade via pertussis toxin-insensitive G proteins in a time- and dose-dependent manner. The inability of G(q/11) and G(12/13) proteins to activate IKK/NFkappaB by SSTR2 in transfected human embryonic kidney 293 cells and the lack of Galpha(16) in AR42J cells suggested a possible role of Galpha(14) in mediating SSTR2-induced responses. This regulatory role of Galpha(14) was further confirmed by the activation of IKK and NFkappaB in human embryonic kidney 293 cells expressing SSTR2 and Galpha(14) upon induction. The stimulatory effect of Gbeta(1)gamma(2) and the abrogation by overexpressing transducin confirmed the participation of Gbetagamma in SSTR2-mediated IKK/NFkappaB activation. By the application of specific inhibitors and dominant negative mutants, phospholipase Cbeta, protein kinase C, and calmodulin-dependent kinase II were shown to be involved in SSTR2-induced responses. Inhibition of c-Src and numerous intermediates, including Ras, Raf-1 kinase, MEK1/2, along with the extracellular signal-regulated kinase cascade attenuated somatostatin-mediated IKK/NFkappaB activation. Although c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) were also stimulated by SSTR2, suppression of these two MAPKs was ineffective in altering the somatostatin-mediated responses. Similar results were also obtained using AR42J cells. These data suggest that activation of the IKK/NFkappaB signaling cascade by SSTR2 requires a complicated network consisting of Galpha(14) and multiple intermediates.
Liu
Andrew M F
AM
Department of Biochemistry, Molecular Neuroscience Center, and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Wong
Yung H
YH
D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005799:Genes, Dominant; D017930:Genes, Reporter; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D015151:Immunoblotting; D007527:Isoenzymes / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D054799:Phospholipase C beta; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D015293:Transducin / Q000378:metabolism; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases
C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D007527:Isoenzymes; D016328:NF-kappa B; D017481:Receptors, Somatostatin; C093733:somatostatin receptor 2; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D051550:I-kappa B Kinase; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C119109:GNA14 protein, human; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins; D015293:Transducin