Gene expression for calpain isozymes in human hematopoietic system cells.
Calpain (EC 3.4.22.17; Ca2(+)-dependent cysteine endopeptidase) is known to exist in two forms of isozyme. Calpain I requires low (or microM)-Ca2+ for activation and calpain II requires high (or mM)-Ca2+. Both isozymes consist of one heavy (approx.80 kDa) and one light (approx. 30 kDa) subunit each. The heavy subunits of isozymes I and II are different genetic products, while the light subunits are identical. Antibodies respectively specific for the heavy subunits of pig calpains I and II were raised in rabbits, and the affinity-purified IgG proteins were used for Western blot analysis. When 23 human hematopoietic system cells were examined for the degree of their expression of the genes for calpains I and II, all of them were found to contain calpain I of detectable amounts in their cytosolic fluid. By contrast, only nine cell-line cells were positive in calpain II, and they were, without exception, the lineage which had been infected with HTLV-I, the retrovirus responsible for human adult T-cell leukemia. The enhanced production of calpain II in HTLV-I infected T-cells was also confirmed by running chromatographic analyses on the homogenates of these cells, and comparing them with those of uninfected T-cells. When YT-C3 cell, which is an uninfected, natural killer-like cell, was transfected with HTLV-I gene, the resulting transformed stable cells, YT-4 and YT-5.1, were found to produce increased amounts of calpain II concomitant with that of interleukin (IL)-2 receptor protein. These results suggest that the gene expression for calpain isozymes may vary during the course of differentiation of T-lymphocytes. The mechanism of regulation of calpain isozyme genes and the biological significance of the variation in expression during differentiation still remain unanswered.
Department of Clinical Science, Faculty of Medicine, Kyoto University, Japan.
T
T
Murachi
Y
Y
Adachi
M
M
Hatanaka
G
G
Ishihara
E
E
Takano
Y
Y
Yamagata
R
R
Kannagi
D000818:Animals; D002154:Calpain / Q000235:genetics*; D002460:Cell Line; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D008957:Models, Genetic
D007527:Isoenzymes; D002154:Calpain