Lp82 is the dominant form of calpain in young mouse lens

H. Ma, I. Hata, M. Shih, C. Fukiage, Y. Nakamura, M. Azuma, T. R. Shearer

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


The purpose of this study was to characterize Lp82 calpain in normal mouse. Lp82 is a lens-specific, calcium-activated isozyme from the calpain super family of cysteine proteases (EC 34.22.17). RT-PCR and molecular cloning were performed on total RNA from 12 day-old mice. Lp82 and m-calpain protein levels and proteolytic activities in lenses were measured by casein zymography, immunoblotting, and ELISA after partial purification by DEAE- HPLC. The 2334-bp cDNA encoding for mouse Lp82 contained a single large open reading frame encoding a protein of 709 amino acid residues with a calculated molecular weight of 82.2 kDa and a predicted pI of 5.8. The amino acid sequence of mouse lens Lp82 was 99 % homologous to rat lens Lp82. As in rat, mouse lens Lp82 showed a unique N-terminus and deletion of the IS1 and IS2 regions. In contrast to rat, Lp82 was the dominant calpain in young mouse lens. Lp82 was lens-specific, and the lens nucleus contained the highest specific activity of Lp82 and very little m-calpain. Endogenous Lp82 in lens soluble proteins was activated by addition of calcium and caused limited proteolysis of crystallins even in the presence of large amounts of recombinant domain I from the natural calpain inhibitor calpastatin. Loss of Lp82 protein accompanied aging of mouse lens. Lp82 may be responsible for a major portion of crystallin proteolysis occurring during normal lens development and maturation, or during cataract formation in young mice.

Original languageEnglish (US)
Pages (from-to)447-456
Number of pages10
JournalExperimental Eye Research
Issue number4
StatePublished - Apr 1999
Externally publishedYes


  • Casein zymography
  • Immunoblot
  • Lens maturation
  • Lp82
  • M-calpain
  • Molecular cloning
  • Mouse lens
  • mRNA

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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