title: Inhibition of Rho-kinase induces alphaB-crystallin expression in lens epithelial cells.
abstract: The small heat shock protein, alphaB-crystallin, has been shown to interact with actin and intermediate filament proteins. However, little is known regarding the cellular mechanisms regulating such interactions. In this study, we explored the role of the Rho/Rho-kinase pathway in alphaB-crystallin distribution and expression in porcine lens epithelial cells. alphaB-crystallin was distributed uniformly throughout the cytoplasm and did not exhibit any unique redistribution in response to actin depolymerization induced by Rho/Rho-kinase inhibitors (C3-exoenzyme or Y-27632) or by overexpression of the dominant negative mutant of Rho-kinase (DNRK) in porcine lens epithelial cells. Interestingly, alphaB-crystallin levels markedly increased in lens epithelial cells treated with the inhibitors of Rho/Rho-kinase proteins (lovastatin, Y-27632 or DNRK) while a protein kinase C inhibitor (GF109203x) was found to have no effect. Further, Y-27632 showed a dose (2-50 microM) response effect on alphaB-crystallin induction. Nocodazole, a microtubule-depolymerizing agent, elicited an increase in alphaB-crystallin levels but latrunculin, an actin depolymerizing agent, did not show any significant effect. Pretreatment with cycloheximide or genistein blocked the Rho-kinase inhibitor-induced increase in alphaB-crystallin protein levels. Rho-kinase inhibitor-induced increases in alphaB-crystallin levels were found to be associated with activation of P38 mitogen-activated protein kinase (MAPK). These results suggest that Rho/Rho-kinase negatively regulates alphaB-crystallin expression, and this response appears to be dependent on tyrosine-protein kinase and P38 MAPK function. Finally, alphaB-crystallin induction appears to be better correlated with the direct inhibition of Rho/Rho-kinase than with actin depolymerization per se.
authors.affiliation: Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Rahul N
authors.initials: RN
authors.lastname: Khurana
authors.forename: Rupa Latha
authors.initials: RL
authors.lastname: Maddala
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shimokawa
authors.forename: J
authors.initials: J
authors.lastname: Samuel Zigler
authors.forename: David L
authors.initials: DL
authors.lastname: Epstein
authors.forename: P
authors.initials: P
authors.lastname: Vasantha Rao
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins; D003459:Crystallins / Q000032:analysis / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007908:Lens, Crystalline / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D022502:Stress Fibers / Q000737:chemistry / Q000187:drug effects / Q000648:ultrastructure; D013552:Swine; D048051:p38 Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D003459:Crystallins; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C108830:Y 27632; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins