Activation of PI3K-Akt-GSK3beta pathway mediates hepatocyte growth factor inhibition of RANTES expression in renal tubular epithelial cells.
Hepatocyte growth factor (HGF) was recently reported to ameliorate renal inflammation in a rat model of chronic renal failure. HGF exerted its action through suppression of RANTES expression in renal tubules. In the present study, we utilized an in vitro model of human kidney proximal tubule epithelial cells (HKC) to elucidate the mechanisms of RANTES suppression by HGF. HGF significantly suppressed basal and TNF-alpha-induced mRNA and protein expression of RANTES in a time and dose dependent fashion. HGF elicited PI3K-Akt activation and inhibited GSK3, a downstream transducer of PI3K-Akt, by inhibitory phosphorylation at Ser-9. When the PI3K-Akt pathway was blocked by wortmannin, HGF inhibition of RANTES was abrogated, demonstrating that the PI3K-Akt pathway is necessary for HGF action. In addition, specific inhibition of GSK3 activity by lithium ion suppressed basal and TNF-alpha-induced RANTES expression, reminiscent of the action of HGF. To further investigate the role of GSK3 in modulating RANTES expression, we examined the effect of forced expression of wild type GSK3beta or an uninhibitable mutant GSK3beta, in which the regulatory Ser-9 residue is changed to alanine (S9A-GSK3beta) in HKC. Overexpression of wild type GSK3beta did not alter the inhibitory action of HGF on RANTES. In contrast, expression of S9A-GSK3beta abolished HGF inhibition of basal and TNF-alpha stimulated RANTES expression. These findings suggest that PI3K-Akt activation and subsequent inhibitory phosphorylation of GSK3beta are required for HGF-induced suppression of RANTES in HKC.
Gong
Rujun
R
Division of Renal Diseases, Department of Medicine, Brown University Medical School, Providence, RI 02903, USA. rgong@Brown.edu <rgong@Brown.edu>
Rifai
Abdalla
A
Dworkin
Lance D
LD
D002460:Cell Line; D018946:Chemokine CCL5 / Q000037:antagonists & inhibitors*; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D017228:Hepatocyte Growth Factor / Q000502:physiology*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018946:Chemokine CCL5; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494918:AKT1 protein, human; C000605506:GSK3B protein, human; C000605508:Gsk3b protein, rat