Effect of calpain on the degradation of tau protein in rat brain cortex extracts

Zheng Yu Fang, Shi Jie Liu, Xiao Chuan Wang, Rong Liu, Qun Wang, Zheng Yue Chen, Jian Zhi Wang

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Abstract

Calpain is a calcium-activated protease and has two ubiquitously distributed mammalian isoforms, namely calpain 1 (calpain I, μ-calpain and CAPN1) and calpain 2 (calpain II, m-calpain and CAPN2). Calpains regulate the function of many proteins by limited proteolysis. To determine the nature of different subtypes of calpain on degradation of microtubule-associated protein tau, the rat cortex extracts were incubated with 0.2 mmol/L, 1 mmol/L, 3 mmol/L and 5 mmol/L of CaCl2 for 15 min at 37°C, respectively, and it was found that Ca2+ treatment at concentrations 1-5 mmol/L led to significant proteolysis of the tau protein and this degradation was blocked by calpain inhibitor, calpeptin. In addition, when the extracts containing 1 mmol/ L CaCl2 were treated with μ-calpain inhibitor (0.05 μmol/L of calpastatin) or m-calpain inhibitor (100 μmol/L calpain inhibitor IV) or both, the Ca2+-induced degradation of tau protein was blocked to about 8.6%, 92.5% and 97.8% compared with the group with 1 mmol/L CaCl 2, respectively. These data suggest that both μ-calpain and m-calpain in brain cortex extracts are activated by Ca2+ and both of them degraded tau protein, although, m-calpain plays a more important role in proteolysis of the tau protein.

Original languageEnglish
Pages (from-to)629-634
Number of pages6
JournalActa Biochimica et Biophysica Sinica
Volume35
Issue number7
Publication statusPublished - 22 Aug 2003
Externally publishedYes

Keywords

  • Alzheimer disease
  • Calcium
  • Calpain
  • Tau protein

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