Calpains in the human lens: relations to membranes and possible role in cataract formation.
Calpains are Ca-activated neutral proteases present in all cells together with an endogenous inhibitor, calpastatin. Proposed substrates are; cytoskeletal proteins like microtubules and actin, protein kinases such as PKC and membrane-bound enzymes like Ca-ATPase and the Ca-channel. In lenses from different species calpains have been detected in decreasing amounts from the epithelium to the cortex to the nucleus. Several substrates for calpain in the lens have been demonstrated: crystallins, vimentin, actin, beaded filaments and MP26 among others. Both studies on animal models and capsulorhexis indicate that calpains are mainly involved in cortical cataract.
Andersson
M
M
Department of Anatomy and Cell Biology, University of Göteborg, Sweden.
Sjöstrand
J
J
Karlsson
J O
JO
D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002386:Cataract / Q000378:metabolism; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D007908:Lens, Crystalline / Q000201:enzymology*; D013379:Substrate Specificity
D002135:Calcium-Binding Proteins; C033668:calpastatin; D002154:Calpain; D002118:Calcium