TGF-beta-activating kinase-1 inhibits cell cycle and expression of cyclin D1 and A in LLC-PK1 cells.
BACKGROUND
Transforming growth factor-beta (TGF-beta) is known to play an important role in the pathophysiology of renal tubular disease. Researchers have recently identified a novel mitogen-activated protein kinase kinase kinase (MAPKKK), TAK (TGF-beta activated kinase)1, which stimulates the MKK3/6-p38K pathway. The purpose of our study was to investigate the functional role of the TAK1-MKK3/6-p38K pathway and classical MAPK cascades in the progression of the cell cycle in renal tubular cells.


METHODS
The constitutive active form and negative form of TAK1 (TAK1dN and TAK1K63W, respectively), and active and negative forms of the p42/44 MAPK-activator, MKK1 (S222E and S222A, respectively) were transfected to LLC-PK1 cells. Western blot analyses and promoter-luciferase assay of cyclins D1, D2, D3, E, and A were performed, and cell cycle progression was analyzed by FACS scan.


RESULTS
TAK1dN stimulated MKK6 and p38K activity and inhibited the percentage of the S and G2/M phases. TAK1K63 W inhibited TGF-beta-stimulated MKK6 and p38K activity. Cyclin D1 and cyclin A protein levels and promoter activities were negatively regulated by TAK1dN. In contrast, overexpression of the active form of p42/44 MAPK-activator, MKK1, increased cyclin D1 and A promoter activity and protein levels.


CONCLUSIONS
The growth-inhibitory effects of TGF-beta are at least partially mediated by the TAK1-MKK6-p38K pathway. Cyclin D1 and A promoter activity and cell cycle progression in renal tubular cells are negatively regulated by the TAK1-MKK6-p38K pathway and positively regulated by the MKK1-p42/44MAPK pathway.
Terada
Y
Y
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan. yterada.med2@med.tmd.ac.jp
Nakashima
O
O
Inoshita
S
S
Kuwahara
M
M
Sasaki
S
S
Marumo
F
F
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019925:Cyclin A / Q000235:genetics*; D019938:Cyclin D1 / Q000235:genetics*; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry; D016193:G1 Phase / Q000502:physiology; D016195:G2 Phase / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D017930:Genes, Reporter; D007684:Kidney Tubules / Q000166:cytology / Q000201:enzymology*; D018374:LLC-PK1 Cells; D048369:MAP Kinase Kinase 1; D048669:MAP Kinase Kinase 6; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D016296:Mutagenesis / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D016196:S Phase / Q000502:physiology; D013552:Swine; D013936:Thymidine / Q000378:metabolism / Q000494:pharmacology; D014316:Tritium; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019925:Cyclin A; D019938:Cyclin D1; D004247:DNA; D048369:MAP Kinase Kinase 1; D048669:MAP Kinase Kinase 6; D020930:MAP Kinase Kinase Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D013936:Thymidine; D014316:Tritium; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7