Specific increase in calcium-activated neutral protease with low calcium sensitivity (m-calpain) in proerythroblastic K562 cell line cells induced to differentiation by phorbol 12-myristate 13-acetate.
Changes in the level of calcium-activated neutral proteases (calpains) in K562 cells induced to differentiate by phorbol 12-myristate 13-acetate (PMA) were examined by an immunohistochemical technique and Western blot analysis. A remarkable increase in m-calpain (high-Ca(2+)-requiring form) level was detected after PMA-treatment, while there was no significant difference in mu-calpain (low-Ca(2+)-requiring form) level between PMA-treated and untreated K562 cells. To confirm whether the increase in m-calpain is specific to PMA-induced differentiation, we examined changes in calpain in K562 cells cultured in serum-free medium and in synchronized cells. The results indicate that the increase has no relation to growth arrest or to cell cycle. PMA-treated cells exhibited increased nonspecific esterase activity, suggesting monocytic differentiation. Immunoelectron microscopic study showed the reactions of dense deposits with monoclonal anti-m-calpain antibody on cell membranes, on membranes of coated vesicles, and on rough endoplasmic reticulum of K562 cells after 26 h of PMA treatment.
Nakamura
M
M
Department of Enzyme Biochemistry, Tokyo Metropolitan Institute of Gerontology, Japan.
Mori
M
M
Morishita
Y
Y
Mori
S
S
Kawashima
S
S
D015153:Blotting, Western; D002154:Calpain / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002467:Cell Nucleus / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004900:Erythroblasts / Q000201:enzymology*; D006801:Humans; D007124:Immunoenzyme Techniques; D066298:In Vitro Techniques; D015466:Leukemia, Myeloid, Chronic-Phase; D008854:Microscopy, Electron; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors; D014407:Tumor Cells, Cultured
D002154:Calpain; D013755:Tetradecanoylphorbol Acetate