The PI3-kinase-Akt pathway promotes mesangial cell survival and inhibits apoptosis in vitro via NF-kappa B and Bad.
While the serine/threonine protein kinase Akt has attracted attention as a mediator of survival (anti-apoptotic) signal, the regulation and function of the PI3-kinase-Akt pathway in mesangial cells is not well known. To explore the significance of the PI3-kinase-Akt pathway, this study used PI3-kinase inhibitors (Wortmannin and LY294002) and recombinant adenoviruses encoding a dominant-active mutant of Akt (AxCAmyrAkt) and a dominant-negative mutant of Akt (AxCAAkt-AA) in cultured rat mesangial cells. Apoptotic signals were measured by nucleosomal laddering of DNA, caspase 3 assay, and cell death detection ELISA. The PI3 kinase inhibitors and dominant-negative mutant of Akt increased the apoptotic signals in the presence of platelet-derived growth factor (PDGF), while the dominant-active mutant of Akt prevented apoptosis induced by a serum-free medium. In separate experiments, we further investigated downstream signals of Akt in mesangial cells. While PDGF activated NF-kappa B and phosphorylated Bad, these reactions were inhibited by overexpression of the dominant-negative mutant of Akt as well as the PI3-kinase inhibitors. These data indicate, firstly, that Akt is phosphorylated by PDGF, and secondly, that the activated Akt prevents apoptotic changes via activation of NF-kappa B and phosphorylation of Bad in mesangial cells. This study investigated whether it is Bad phosphorylation or NF-kappa B activation that provides the anti-apoptotic effects of Akt, and the data suggested that NF-kappa B is probably the principal contributor to the downstream activation of the PI3-kinase-Akt pathway. The findings suggest that the PI3-kinase-Akt pathway acts as a survival signal and plays a key role in the regulation of apoptotic change in mesangial cells principally via NF-kappa B.
Shimamura
Haruko
H
The Homeostasis Medicine and Nephrology, Tokyo Medical and Dental University, Tokyo, Japan.
Terada
Yoshio
Y
Okado
Tomokazu
T
Tanaka
Hiroyuki
H
Inoshita
Seiji
S
Sasaki
Sei
S
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D016328:NF-kappa B / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D000077191:Wortmannin; D051025:bcl-Associated Death Protein
D000730:Androstadienes; D002352:Carrier Proteins; D002867:Chromones; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D009025:Morpholines; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; D051025:bcl-Associated Death Protein; C494821:Bad protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494920:Akt1 protein, rat