Distribution and expression of calpastatin in human hematopoietic system cells

Thirteen cell lines of the human hematopoietic system were tested for expression of calpastatin at three different levels (mRNA, product and activity). The amount of calpastatin product and its inhibitory activity varied markedly depending upon cell types or human T-cell leukemia virus type I infection, although there were difference in the expression at the transcriptional level. Cell lines with high content of calpastatin comprised T-cell lineage infected by human T-cell leukemia virus type I, B-cell line and myelocytic leukemia cell lines. Non-infected T-cell lines and null cell line revealed themselves as poor in both calpastatin products and inhibitor activities. Two different molecular forms of calpastatin were observed: a 102-kDa form in T- and B-cell lines and a 94-kDa form in one of myelocytic cells. Three mRNA species of calpastatin (3.8, 3.0 and 2.5 kb) were identified in human hematopoietic system cells.