Calpain II induced insolubilization of lens β-crystallin polypeptides may induce cataract

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Abstract

Addition of calpain II (EC 3.4.22.17) to soluble proteins from 10-day-old rat lens caused an increase in turbidity and production of water-insoluble protein. The insolubilization increased with higher concentrations of both lens protein and calpain II, it could be prevented by the cysteine protease inhibitor E-64; it required at least 0.5 mM Ca2+, it was limited to 6% of the soluble protein present and resulted from precipitation β-crystallin polypeptides. When compared by two-dimensional electrophoresis, the insoluble β-crystallin polypeptides produced by calpain II were similar to insoluble β-crystallin polypeptides found incataractous lenses. Trypsin also caused insolubilization of β-crystallin polypeptides, but these polypeptides were unlike polypeptides produced during cataract formation. These data suggested that the loss of solubility was due to a specific removal of N/or C-terminal extensions from β-crystallin polypeptides by calpain II, and that a similar process may occur in vivo during cataract formation. It is hypothesized that the insoluble protein produced by calpain II causes cataract by increasing light scatter in the lens.

Original languageEnglish (US)
Pages (from-to)210-216
Number of pages7
JournalBBA - Molecular Basis of Disease
Volume1139
Issue number3
DOIs
StatePublished - Jul 7 1992

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Keywords

  • Calpain II
  • Cataract
  • Lens
  • β-Crystallin

ASJC Scopus subject areas

  • Molecular Medicine
  • Molecular Biology

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