Degradation of human aquaporin 0 by m-calpain

H. Ma, M. Azuma, T. R. Shearer

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Opacities (cataracts) in the lens of the eye are a leading cause of preventable blindness. Aquaporins function as water channels, and the C-terminus is postulated as a regulatory domain. The C-terminal domain of aquaporin 0 (AQP0) develops numerous truncation sites during lens aging. The purpose of the present experiment was to determine if the calcium-activated protease m-calpain (EC was responsible for truncation of human AQP0. AQP0 was isolated from young human donors, incubated with recombinant m-calpain, and the cleavage sites on the released peptides were determined by on-line electrospray ionization mass spectrometry. We found that four cleavage sites on human AQP0 could be tentatively assigned to m-calpain. This is the first evidence for possible calpain activity in human lens. Because the cause(s) of 17 other cleavage sites was unknown, the data also suggested that other, as yet unknown, proteases or non-enzymatic mechanisms are more active than calpain in human lens.

Original languageEnglish (US)
Pages (from-to)6745-6748
Number of pages4
JournalFEBS Letters
Issue number30
StatePublished - Dec 19 2005
Externally publishedYes


  • Aquaporin 0 (AQP0)
  • Calpains
  • Human lens
  • Post-translation modifications

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology


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