Analysis of gene expression of calpain and calpastatin

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Calpain is an intracellular Ca^<2+>-dependent cysteine endopeptidase, and calpastatin is an endogenous specific inhibitor of calpain. Both proteins constitute an intracellular regulatory system operating in response to Ca^<2+> signaling. We cloned the CDNA for pig heart calpastatin and investigated structure-function relationships. The inhibitor consists of four inhibitory domains with mutually homologous sequences. A human calpastatin genomic DNA clone- was isolated, and synthetic oligopeptide corresponding to an exon of the human calpastatin gene showed strong inhibition against calpain I and calpain. When various hematopoietic cells were screened by Westem blot analysis, using antibodies specific for calpain I and for calpain 11, respectively ; HTLV-L infected cells were found to express high level ofcalpain 11, whereas HTLV-l non infected T cells did not express any appreciable amount of calpain 11. Calpain I was expressed in all the cells tested. Calpastatin gene expression was also found to be elevated in HTLV-L infected cells.