title: Requirement of mitogen-activated protein kinase kinase 3 (MKK3) for activation of p38alpha and p38delta MAPK isoforms by TGF-beta 1 in murine mesangial cells.
abstract: Transforming growth factor-beta1 (TGF-beta1) is a potent inducer of extracellular matrix (ECM) synthesis that leads to renal fibrosis. Intracellular signaling mechanisms involved in this process remain incompletely understood. Mitogen-activated protein kinase (MAPK) is a major stress signal-transducing pathway, and we have previously reported activation of p38 MAPK by TGF-beta1 in rat mesangial cells and its role in the stimulation of pro-alpha1(I) collagen. In this study, we further investigated the mechanism of p38 MAPK activation by TGF-beta1 and the role of MKK3, an upstream MAPK kinase of p38 MAPK, by examining the effect of targeted disruption of the Mkk3 gene. We first isolated glomerular mesangial cells from MKK3-null (Mkk3-/-) and wild-type (Mkk3+/+) control mice. Treatment with TGF-beta1 induced rapid phosphorylation of MKK3 as well as p38 MAPK within 15 min in cultured wild-type (Mkk3+/+) mouse mesangial cells. In contrast, TGF-beta1 failed to induce phosphorylation of either MKK3 or p38 MAPK in MKK3-deficient (Mkk3-/-) mouse mesangial cells, indicating that MKK3 is required for TGF-beta1-induced p38 MAPK activation. TGF-beta1 selectively activated the p38 MAPK isoforms p38alpha and p38delta in wild-type (Mkk3+/+) mesangial cells, but not in MKK3-deficient (Mkk3-/-) mesangial cells. Thus, activation of p38alpha and p38delta is dependent on the activation of upstream MKK3 by TGF-beta1. Furthermore, MKK3 deficiency resulted in a selective disruption of TGF-beta1-stimulated up-regulation of pro-alpha1(I) collagen expression but not TGF-beta1 induction of fibronectin and PAI-1. These data demonstrate that the MKK3 is a critical component of the TGF-beta1 signaling pathway, and its activation is required for subsequent p38alpha and p38delta MAPK activation and collagen stimulation by TGF-beta1.
authors.affiliation: Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Rui
authors.initials: R
authors.lastname: Ma
authors.forename: Richard A
authors.initials: RA
authors.lastname: Flavell
authors.forename: Mary E
authors.initials: ME
authors.lastname: Choi
mesh_terms: D051698:Activating Transcription Factor 2; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D003094:Collagen / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D005920:Glomerular Mesangium / Q000166:cytology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048292:Mitogen-Activated Protein Kinase 13; D048308:Mitogen-Activated Protein Kinase 14; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism* / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D011505:Protein-Tyrosine Kinases / Q000378:metabolism* / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1
chemical_list: D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D020033:Protein Isoforms; D011994:Recombinant Proteins; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D003094:Collagen; D048292:Mitogen-Activated Protein Kinase 13; D011505:Protein-Tyrosine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048308:Mitogen-Activated Protein Kinase 14; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048670:MAP Kinase Kinase 4; C482530:MAP2K3 protein, human; C482531:Map2k3 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases