| Abstrakt: |
To compare the effects of two serine-threonine protein kinase inhibitors in a mouse lens culture system previously designed to investigate cortical cataracts caused by L-buthionine sulfoximine (BSO), inhibitor of GSH biosynthesis. H7 (50μM), inhibitor of protein kinase A (PKA) and protein kinase C (PKC), did not cause cataracts, but inhibited BSO cataract development. By contrast, 25 μM H89, selective inhibitor of PKA, caused large annular cortical cataracts and 100fold elevation of Na[sup+]/K[sup+] within 30 hr in day 10 lenses, in either the presence or absence of BSO. H89 cataracts were also seen in day 12 and day 21 lenses. [sup32]P-labeling of day 12 lenses pretreated with H89 displayed more than 80% decrease in phosphorylation of alphaA crystallin, a known substrate of PKA, in the insoluble protein fraction. 2Dgel electrophoresis of day 12 H89 cataracts lens fractions revealed limited degradation of alpha and beta crystallins, degradation of cytoskeletal proteins, and elevated lens Ca²[sup+] (>4 nmol/mg wet wt.), suggesting Ca²[sup+]activated proteolysis. High Na[sup+]/K[sup+] cataracts are induced by H89, selective inhibitor of PKA, but not by H7, an inhibitor of both PKA and PKC that impeded BSO-induced Na[sup+]/K[sup+] elevation and cataracts. These results suggest contrasting effects of PKA and PKC on lens cation transport and cortical cataract development. [ABSTRACT FROM AUTHOR] |
