Herbimycin A and geldanamycin inhibit okadaic acid-induced apoptosis and p38 activation in NRK-52E renal epithelial cells.
It is important to understand the mechanisms by which phosphorylation-dependent events play a role in regulation of apoptosis in toxicant-metabolizing organs such as the kidney. Our previous work demonstrated that the toxicant and phosphatase inhibitor okadaic acid induces apoptosis of renal epithelial cells via a mechanism that appears to involve the modulation of c-raf-1, p38 kinase, and extracellular regulatory kinase (ERK) cascades. Using the benzoquinone ansamycins and tyrosine kinase inhibitors geldanamycin and herbimycin A, we examined the contribution of tyrosine phosphorylation and c-raf-1 activities to okadaic acid-induced apoptosis. In this report we show that both geldanamycin and herbimycin A protected NRK-52E cells from okadaic acid-induced apoptosis, abrogated the overall okadaic acid-induced kinase activation, and specifically inhibited activation of p38 kinase by okadaic acid. Herbimycin A and geldanamycin also abrogated okadaic-acid induced morphologic changes such as cell rounding and cell membrane blebbing. Herbimycin A and geldanamycin caused pronounced cell spreading, cell flattening, and a decrease in okadaic acid-induced loss of actin filaments. Interestingly, herbimycin A showed more potent inhibitory effect than geldanamycin, and herbimycin A alone inhibited okadaic acid-induced movement of p38 kinase into the cytosol. These results imply that decreased p38 activity and its cytosolic translocation together with cellular resistance to cytoskeletal disorganization may play a significant role in resistance to phosphorylation-dependent apoptosis. Furthermore, the results imply that changes in cell shape may partially modulate the observed alterations in signal transduction induced by okadaic acid.
Davis
M A
MA
Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA.
Carbott
D E
DE
D000199:Actins / Q000378:metabolism; D051698:Activating Transcription Factor 2; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D016227:Benzoquinones; D002460:Cell Line; D048429:Cell Size / Q000187:drug effects; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D007093:Imidazoles / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D047029:Lactams, Macrocyclic; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019319:Okadaic Acid / Q000037:antagonists & inhibitors* / Q000494:pharmacology* / Q000633:toxicity; D010766:Phosphorylation / Q000187:drug effects; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D011809:Quinones / Q000494:pharmacology*; D051381:Rats; D017828:Rifabutin / Q000494:pharmacology / Q000031:analogs & derivatives; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
D000199:Actins; D051698:Activating Transcription Factor 2; D016227:Benzoquinones; D002843:Chromatin; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007093:Imidazoles; D047029:Lactams, Macrocyclic; D011725:Pyridines; D011809:Quinones; D014157:Transcription Factors; D019319:Okadaic Acid; D017828:Rifabutin; C020754:herbimycin; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C001277:geldanamycin