In vitro precipitation of rat lens crystallins by calpain I--a calpain requiring low amounts of calcium for activation.
The overall goal of this study was to provide data on the function and physiologic significance of lens calpain I, a cysteine protease requiring low amounts of calcium for activation. Reverse-transcriptase polymerase chain reaction was used to detect mRNAs for calpains I and II in young rat lenses. An in vitro model of crystallin precipitation was used to assess the ability of calpain I to induce hydrolysis and precipitation of crystallins. We found that incubation of crystallins with purified calpain I was indeed a powerful inducer of crystallin precipitation. However, mRNA levels for calpain I in whole lens appeared to be lower compared to calpain-II mRNA. Participation of calpain I in crystallin precipitation during normal maturation of rodent lenses or cataract formation is thus theoretically possible, but unlikely, because of the low level of expression of calpain I.
Shearer
T R
TR
Department of Oral Molecular Biology, Oregon Health Sciences University, Portland 97201, USA.
Throneburg
D B
DB
Shih
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002154:Calpain / Q000235:genetics / Q000502:physiology*; D011232:Chemical Precipitation; D003459:Crystallins / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D007908:Lens, Crystalline / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D003459:Crystallins; D017931:DNA Primers; D012333:RNA, Messenger; D002154:Calpain; D002118:Calcium