Low activity by the calpain system in primate lenses causes resistance to calcium-induced proteolysis

E. Nakajima, R. D. Walkup, H. Ma, T. R. Shearer, M. Azuma

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The human genome contains 14 genes for 80 kDa catalytic subunit of the calcium-activated protease calpain (EC 34.22.17), yet no calpain-like cleavage sites have been detected on human lens crystallins in vivo. The purpose of the present study was to provide a comprehensive study of calpain activation in human and macaque lenses developing experimental cataract due to lens culture in ionophore A23187. Zymography was used to measure calpain activity; SDS-PAGE and immunoblotting were used to detect hydrolysis of potential lens protein substrates. Quantitative PCR was used to measure transcripts for calpains and the endogenous inhibitor calpastatin. We found that the lack of appreciable calpain-induced proteolysis in primate lenses is most likely due to relatively low levels of endogenous calpain activity compared to the high levels of endogenous calpain inhibitor, calpastatin.

Original languageEnglish (US)
Pages (from-to)593-601
Number of pages9
JournalExperimental Eye Research
Volume83
Issue number3
DOIs
StatePublished - Sep 1 2006

Keywords

  • calcium
  • cataract
  • lens
  • protease

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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