Regulation of caspase-3 and -9 activation in oxidant stress to RTE by forkhead transcription factors, Bcl-2 proteins, and MAP kinases.
Cytotoxicity to renal tubular epithelial cells (RTE) is dependent on the relative response of cell survival and cell death signals triggered by the injury. Forkhead transcription factors, Bcl-2 family member Bad, and mitogen-activated protein kinases are regulated by phosphorylation that plays crucial roles in determining cell fate. We examined the role of phosphorylation of these proteins in regulation of H(2)O(2)-induced caspase activation in RTE. The phosphorylation of FKHR, FKHRL, and Bcl-2 family member Bad was markedly increased in response to oxidant injury, and this increase was associated with elevated levels of basal phosphorylation of Akt/protein kinase B. Phosphoinositol (PI) 3-kinase inhibitors abolished this phosphorylation and also decreased expression of antiapoptotic proteins Bcl-2 and BclxL. Inhibition of phosphorylation of forkhead proteins resulted in a marked increase in the proapoptotic protein Bim. These downstream effects of PI 3-kinase inhibition promoted the oxidant-induced activation of caspase-3 and -9, but not caspase-8 and -1. The impact of enhanced activation of caspases by PI 3-kinase inhibition was reflected on accelerated oxidant-induced cell death. Oxidant stress also induced marked phosphorylation of ERK1/2, P38, and JNK kinases. Inhibition of ERK1/2 phosphorylation but not P38 and JNK kinase increased caspase-3 and -9 activation; however, this activation was far less than induced by inhibition of Akt phosphorylation. Thus the Akt-mediated phosphorylation pathway, ERK signaling, and the antiapoptotic Bcl-2 proteins distinctly regulate caspase activation during oxidant injury to RTE. These studies suggest that enhancing renal-specific survival signals may lead to preservation of renal function during oxidant injury.
Department of Medicine, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Slot 501, 4301 W. Markham St., Little Rock, AR 72205, USA. kaushalgurp@uams.edu
Gur P
GP
Kaushal
Ling
L
Liu
Varsha
V
Kaushal
Xiaoman
X
Hong
Oksana
O
Melnyk
Rohit
R
Seth
Robert
R
Safirstein
Sudhir V
SV
Shah
D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D002470:Cell Survival; D004268:DNA-Binding Proteins; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007684:Kidney Tubules / Q000166:cytology* / Q000201:enzymology; D020928:Mitogen-Activated Protein Kinases / Q000494:pharmacology*; D018384:Oxidative Stress; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000494:pharmacology*; D014157:Transcription Factors; D014162:Transfection; D051025:bcl-Associated Death Protein
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D014157:Transcription Factors; D051025:bcl-Associated Death Protein; D006861:Hydrogen Peroxide; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases