Protein kinase C mediates cisplatin-induced loss of adherens junctions followed by apoptosis of renal proximal tubular epithelial cells.
Cisplatin is a commonly used antitumor agent in the treatment of various human cancers, with nephrotoxicity as a major side effect. Cisplatin causes the loss of cell-cell contacts of renal proximal tubular epithelial cells prior to the onset of apoptosis. We studied the involvement of protein kinase C in these events in the renal epithelial cell line LLC-PK1. Cisplatin caused apoptosis in LLC-PK1 cells, which was directly related to the activation of caspase-3 and DNA fragmentation. Apoptosis was almost completely inhibited by the protein kinase C inhibitors bisindolylmaleimide (Bis) I and Go6983 [2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]-3-(1H-indol-3-yl) maleimide], but not by Go6976 [12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole]. Also, in primary cultured rat renal proximal tubular cells, inhibition of protein kinase C (PKC) inhibited apoptosis. Cisplatin also caused the early loss of cell-cell adhesions, which was associated with the altered localization of the adherens junction-associated protein beta-catenin in association with PKC-mediated phosphorylation of the actincapping protein adducin. These events preceded and were independent of caspase activation. beta-Catenin did not dissociate from E-cadherin. Cisplatin-induced loss of cell-cell contacts was associated with the increased formation of F-actin stress fibers, which was inhibited by Bis I and Go6983 as well as dominant-negative PKC-epsilon. Also, the loss of cell-cell adhesions by cisplatin was prevented by Bis I and Go6983. Activation of protein kinase C with phorbol esters promoted cisplatin-induced loss of cell-cell adhesions as well as apoptosis. In conclusion, the combined data fit a model whereby protein kinase C mediates the cisplatin-induced loss of cellular interactions. Such a loss of these interactions has a role in the onset of apoptosis.
Imamdi
Raoef
R
Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratoria, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
de Graauw
Marjo
M
van de Water
Bob
B
D000199:Actins / Q000378:metabolism; D022005:Adherens Junctions / Q000187:drug effects*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003911:Dextrans; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells / Q000187:drug effects; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007687:Kidney Tubules, Proximal / Q000187:drug effects*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D018374:LLC-PK1 Cells; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013552:Swine; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D051176:beta Catenin
D000199:Actins; D000970:Antineoplastic Agents; D003598:Cytoskeletal Proteins; D003911:Dextrans; D005452:Fluoresceins; D005456:Fluorescent Dyes; D015534:Trans-Activators; D051176:beta Catenin; C052526:fluorescein-dextran; D007770:L-Lactate Dehydrogenase; D011493:Protein Kinase C; D002945:Cisplatin