Identification of a membrane Ig-induced p38 mitogen-activated protein kinase module that regulates cAMP response element binding protein phosphorylation and transcriptional activation in CH31 B cell lymphomas.
The cAMP response element (CRE) binding protein (CREB) is emerging as a key regulatory factor of gene transcription in B lymphocytes; however, the postreceptor pathways that regulate CREB activity and CRE-dependent gene transcription remain largely undefined. We investigated B cell Ag receptor (BCR)-mediated phosphorylation and activation of CREB in the surface IgM+ CH31 B cell lymphoma, which undergoes Ag-dependent cell death. The activity of p38 mitogen-activated protein kinase (MAPK) was increased in response to BCR ligation. Phosphorylation of CREB on serine 133, a modification that positively regulates its trans-activation, was concomitantly increased. Inhibition of p38 MAPK by pretreating CH31 B cells with the highly specific bicyclic imidazole inhibitor, SB203580, reduced BCR-induced CREB phosphorylation. BCR cross-linking also led to increased MAPK-activated protein kinase-2 activity, an enzyme that lies immediately downstream from p38 MAPK; MAPK-activated protein kinase-2 immune complexes phosphorylated a peptide substrate containing the CREB serine 133 phosphoacceptor motif. Given the role of CREB in regulating junB gene expression in mature B lymphocytes, we examined whether p38 MAPK activity was necessary for CRE-dependent junB transcription in CH31 B cells. BCR ligation led to increased junB mRNA levels, which were significantly reduced in CH31 B cells pretreated with SB203580. Activation of a CRE-dependent junB promoter/chloramphenicol acetyltransferase (CAT) reporter gene by the BCR was also blocked by SB203580. Similarly, inhibition of p38 MAPK in surface IgM+ WEHI-231 B cell lymphomas resulted in reduced BCR-induced junB mRNA expression and junB promoter activation. The results implicate a p38 MAPK pathway in BCR-mediated CREB phosphorylation and junB transcriptional activation in B cell lymphomas.
Swart
J M
JM
Department of Biology, Boston College, Chestnut Hill, MA 02467, USA.
Bergeron
D M
DM
Chiles
T C
TC
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism / Q000502:physiology; D002454:Cell Differentiation / Q000276:immunology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004789:Enzyme Activation / Q000276:immunology; D004790:Enzyme Induction / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D016393:Lymphoma, B-Cell / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D015533:Transcriptional Activation / Q000276:immunology*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D016755:Proto-Oncogene Proteins c-jun; D011725:Pyridines; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D012694:Serine; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C093642:SB 203580