Lp82 is the dominant form of calpain in young mouse lens

Exp Eye Res. 1999 Apr;68(4):447-56. doi: 10.1006/exer.1998.0625.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Calpain*
  • Chromatography, High Pressure Liquid
  • Cloning, Molecular
  • Crystallins / metabolism
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / isolation & purification*
  • Cysteine Endopeptidases / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Immunoblotting
  • Isoenzymes / genetics
  • Isoenzymes / isolation & purification*
  • Lens, Crystalline / enzymology*
  • Mice
  • Mice, Inbred Strains
  • Molecular Sequence Data
  • RNA, Messenger / analysis
  • Rats
  • Rats, Sprague-Dawley
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid


  • Crystallins
  • Isoenzymes
  • RNA, Messenger
  • Calpain
  • Cysteine Endopeptidases
  • calpain Lp82