title: p38MAPK acts in the BMP7-dependent stimulatory pathway during epithelial cell morphogenesis and is regulated by Smad1.
abstract: Bone morphogenetic protein (BMP)-7 exerts dose-dependent stimulatory and inhibitory effects during renal branching morphogenesis. Previously, we identified an inhibitory role for activin-like kinase receptors and Smad1 in BMP-dependent inhibition (Piscione, T. D., Phan, T., and Rosenblum, N. D. (2001) Am. J. Physiol. 280, F19-F33). Here we demonstrate a novel role for p38 mitogen-activated kinase (p38(MAPK)) in BMP7-dependent stimulatory signaling. Stimulatory doses (0.25 nm) of BMP7 increased p38(MAPK) activity and stimulated phosphorylation of endogenous activating transcription factor 2 (ATF2) in a p38(MAPK)-dependent manner in murine inner medullary collecting duct (mIMCD-3) cells. In contrast, high doses (10 nm) of BMP7 inhibited p38(MAPK) activity and phosphorylation of endogenous ATF2. Treatment with BMP7 exerted no significant effect on the levels of the phosphorylated forms of endogenous SAPK/JNK or p44 and p42 (ERK1 and ERK2) protein kinases. To investigate the functional importance of p38(MAPK) signaling, we showed that SB203580, a p38(MAPK) inhibitor, blocked the stimulatory effect of BMP7 on mIMCD-3 cell morphogenesis but had no effect on BMP7-dependent inhibition in a three-dimensional culture model. To identify mechanisms by which BMP7-dependent inhibitory signaling suppresses p38(MAPK) activity, we measured p38(MAPK) activity in ligand independent mIMCD-3 models of enhanced and suppressed Smad signaling. Basal activity of p38(MAPK) was decreased in mIMCD-3 cells and in embryonic kidney tissue expressing a constitutively active activin-like kinase receptor, but was increased in mIMCD-3 cells stably expressing a dominant negative form of Smad1. We conclude that BMP7 stimulates renal epithelial cell morphogenesis via p38(MAPK) and that p38(MAPK) activity is negatively regulated by Smad1.
authors.affiliation: Division of Nephrology, Program in Developmental Biology, The Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Ming Chang
authors.initials: MC
authors.lastname: Hu
authors.forename: David
authors.initials: D
authors.lastname: Wasserman
authors.forename: Sunny
authors.initials: S
authors.lastname: Hartwig
authors.forename: Norman D
authors.initials: ND
authors.lastname: Rosenblum
mesh_terms: D051698:Activating Transcription Factor 2; D000483:Alleles; D000818:Animals; D015153:Blotting, Western; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology*; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D007668:Kidney / Q000196:embryology / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D011233:Precipitin Tests; D011725:Pyridines / Q000494:pharmacology; D051785:Smad Proteins; D051898:Smad1 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis; D014162:Transfection; D016212:Transforming Growth Factor beta; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D051785:Smad Proteins; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580