PROPERTIES OF CALPASTATIN FORMS IN RAT-BRAIN

Four recombinant calpastatin forms, deduced from rat brain mRNAs and d iffering in the number of inhibitory repetitive domains from zero to f our, mere expressed and characterized for their inhibitory efficiency on mu- and m-calpain, Although the most effective one is a truncated c alpastatin form composed of the N-terminal region (domain L) and a sin gle inhibitory domain, all inhibitors are more active against mu- calp ain, but are preferentially degraded and inactivated by m-calpain, The protein form composed exclusively of a domain L is deprived of any in hibitory activity but prevents inhibition of calpain by the other calp astatin forms, indicating that this calpastatin region could be releva nt in the recognition of the proteinase, A calpastatin form having mol ecular properties similar to those of the recombinant truncated calpas tatin, has also been found in rat brain. It does not derive from prote olysis of a higher molecular mass precursor. The expression of multipl e calpastatin forms may be relevant for the specific modulation of the different calpain isozymes normally present in a single cell type. (C ) 1998 Federation of European Biochemical Societies.