Differential effects of galactose-induced cataractogenesis on the soluble crystallins of rat lens.
Soluble lens crystallins from 6-10-week-old, galactose-fed, male Sprague-Dawley rats were analyzed by two-dimensional polyacrylamide gel electrophoresis at each of the five Sippel stages of cataractogenesis. Electrophoretograms were compared with similarly analyzed crystallins from comparably aged, chow-fed controls. Polypeptides were assigned to crystallin families and subfamilies on the basis of chromatographic fractionations with Sephadex G-200, superfine. Staining intensities of polypeptides from control lenses remained essentially unchanged throughout the experimental period, while those of the polypeptides from cataractous lenses showed non-uniform changes. Staining of the genomic gamma-crystallins increases up to at least stage 3; by stage 4, staining of gamma-chains, with perhaps those of gamma 5 and gamma 6 excepted, diminishes and in the total cataract, staining of all chains is further reduced. With possibly the addition of one chain, the total number of postsynthetically modified gamma-crystallins in cataractous lenses does not exceed that in the comparably aged normal lens. The genomic alpha- and beta-crystallin polypeptides are sustained close to normal levels up to stages 3 or 2, respectively, after which their gradually falling levels are accompanied by the generation of new species or elevated levels of existing post-translational species. An exception to this behavior is the rapid and total loss of beta B1a, a genomic subunit implicated in the aggregation of beta H-crystallins. Charge heterogeneity and variable pI displayed by beta B1a and other highly cationic beta- and gamma-crystallin polypeptides can be induced during isoelectric focusing and may be due to thiol group oxidation.
Huang
W Q
WQ
Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School, Newark 07103.
Zhang
J P
JP
Fu
S C
SC
D000818:Animals; D002386:Cataract / Q000209:etiology / Q000378:metabolism*; D003459:Crystallins / Q000032:analysis*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D015180:Electrophoresis, Gel, Two-Dimensional; D005690:Galactose / Q000008:administration & dosage; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility
D003459:Crystallins; D004040:Dietary Carbohydrates; D005690:Galactose