title: Requirement for a hsp90 chaperone-dependent MEK1/2-ERK pathway for B cell antigen receptor-induced cyclin D2 expression in mature B lymphocytes.
abstract: A requirement for cyclin D2 in G(1)-to-S phase progression has been definitively established in mature B cells stimulated via the B cell antigen receptor (BCR). However, the identity of constituents of the BCR signaling cascade that leads to cyclin D2 accumulation remains incomplete. We report that inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-1/2 blocked BCR-induced activation of extracellular signal-regulated kinase (ERK). Inhibition of the MEK1/2-ERK pathway was sufficient to abrogate BCR-induced cyclin D2 expression at the mRNA and protein levels. Disruption of endogenous heat shock protein 90 (hsp90) function with geldanamycin abrogated BCR-induced cyclin D2 expression and proliferation. Geldanamycin effects were attributed to a selective depletion of cellular Raf-1 that interrupted BCR-coupled activation of MEK1/2 and ERK. By contrast, signaling through the phosphatidylinositol 3-kinase and protein kinase C pathways was not affected, suggesting that disruption of hsp90 function did not cause a general impairment of BCR signaling. These results suggest that the MEK1/2-ERK pathway is essential for BCR signaling to cyclin D2 accumulation in ex vivo splenic B lymphocytes. Furthermore, these findings imply that hsp90 function is required for BCR signaling through the Raf-1-MEK1/2-ERK pathway but not through the phosphatidylinositol 3-kinase- or protein kinase C-dependent pathways.
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Piatelli
authors.forename: Cheryl
authors.initials: C
authors.lastname: Doughty
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Chiles
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D016227:Benzoquinones; D002070:Butadienes / Q000494:pharmacology; D002455:Cell Division; D002478:Cells, Cultured; D056742:Cyclin D2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis* / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D015151:Immunoblotting; D047029:Lactams, Macrocyclic; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009570:Nitriles / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011809:Quinones / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013154:Spleen / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D002070:Butadienes; D056742:Cyclin D2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D016213:Cyclins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D011809:Quinones; D012313:RNA; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; C486196:Ccnd2 protein, mouse; C113580:U 0126; C482128:MAP2K2 protein, human; C495902:Cdk4 protein, mouse; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C001277:geldanamycin