Regulation of protein phosphorylation of the intermediate-sized filament vimentin in the ciliary epithelium of the mammalian eye.
The intermediate-sized filaments of vimentin-type (Mr = 57,000) have been identified biochemically and immunochemically as a major cytoskeleton component in the ciliary epithelium of the mammalian eye. When human or rabbit ciliary processes, or cultured ciliary epithelial-derived cells were incubated in serum-free medium containing [32P]orthophosphate and any of the following agents: 1) beta-adrenergic agonists (isoproterenol or epinephrine), 2) direct activators of adenylate cyclase (cholera toxin or forskolin), 3) analogs of cyclic AMP (8-Br-cAMP), or 4) prostaglandin E1, the phosphorylation of vimentin was significantly enhanced. The maximal enhancement ranged, in vivo and in vitro, from about 3-fold in human to 5-fold in rabbit, with either 1 mM 8-Br-cAMP or 0.1 microM forskolin. Phosphorylation of vimentin increased in the presence of beta-adrenergic agonists and could be blocked by the antiglaucoma beta-adrenergic antagonist timolol. The alpha-adrenergic agonist phenylephrine had no effect on phosphorylation of vimentin. Indirect immunofluorescence microscopy using a monoclonal antibody, anti-vimentin, allowed the localization of vimentin filaments in cultured ciliary epithelial cells. Treatment of these cells in culture with the catecholamine hormone, isoproterenol (1 microM), resulted in a profound reorganization of vimentin filaments. This may be correlated with the enhanced levels of phosphorylated vimentin observed upon increasing cellular cyclic AMP.
D000818:Animals; D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000032:analysis; D010710:Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011817:Rabbits; D014746:Vimentin / Q000302:isolation & purification / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D010710:Phosphates; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D014746:Vimentin