Integrin-linked kinase mediates bone morphogenetic protein 7-dependent renal epithelial cell morphogenesis.
Bone morphogenetic protein 7 (BMP7) stimulates renal branching morphogenesis via p38 mitogen-activated protein kinase (p38(MAPK)) and activating transcription factor 2 (ATF-2) (M. C. Hu, D. Wasserman, S. Hartwig, and N. D. Rosenblum, J. Biol. Chem. 279:12051-12059, 2004). Here, we demonstrate a novel role for integrin-linked kinase (ILK) in mediating renal epithelial cell morphogenesis in embryonic kidney explants and identify p38(MAPK) as a target of ILK signaling in a cell culture model of renal epithelial morphogenesis. The spatial and temporal expression of ILK in embryonic mouse kidney cells suggested a role in branching morphogenesis. Adenovirus-mediated expression of ILK stimulated and expression of a dominant negative ILK mutant inhibited ureteric bud branching in embryonic mouse kidney explants. BMP7 increased ILK kinase activity in inner medullary collecting duct 3 (IMCD-3) cells, and adenovirus-mediated expression of ILK increased IMCD-3 cell morphogenesis in a three-dimensional culture model. In contrast, treatment with a small molecule ILK inhibitor or expression of a dominant negative-acting ILK (ILK(E359K)) inhibited epithelial cell morphogenesis. Further, expression of ILK(E359K) abrogated BMP7-dependent stimulation. To investigate the role of ILK in BMP7 signaling, we showed that ILK overexpression increased basal and BMP7-induced levels of phospho-p38(MAPK) and phospho-ATF-2. Consistent with its inhibitory effects on IMCD-3 cell morphogenesis, expression of ILK(E359K) blocked BMP7-dependent increases in phospho-p38(MAPK) and phospho-ATF-2. Inhibition of p38(MAPK) activity with the specific inhibitor, SB203580, failed to inhibit BMP7-dependent stimulation of ILK activity, suggesting that ILK functions upstream of p38(MAPK) during BMP7 signaling. We conclude that ILK functions in a BMP7/p38(MAPK)/ATF-2 signaling pathway and stimulates epithelial cell morphogenesis.
Leung-Hagesteijn
Chungyee
C
Cancer Research Program, Research Institute, Hospital for Sick Children, 555 University Ave., Toronto, Ontario M5G 1X8, Canada.
Hu
Ming Chang
MC
Mahendra
Ahalya S
AS
Hartwig
Sunny
S
Klamut
Henry J
HJ
Rosenblum
Norman D
ND
Hannigan
Gregory E
GE
D051698:Activating Transcription Factor 2; D000818:Animals; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology / Q000502:physiology*; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000196:embryology*; D051379:Mice; D009024:Morphogenesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D009154:Mutation / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099200:Scaffold Protein ILK
D051698:Activating Transcription Factor 2; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D007093:Imidazoles; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D048051:p38 Mitogen-Activated Protein Kinases; D000099200:Scaffold Protein ILK; C497106:Atf2 protein, mouse; C093642:SB 203580