Modulation of the activity of calcium-activated neutral proteases (calpains) in chronic lymphocytic leukemia (B-CLL) cells.
Decreased susceptibility to apoptosis and impaired proliferative control are thought to be responsible for prolonged life span and accumulation of chronic lymphocytic leukemia (B-CLL) cells. The activity of calpains (calcium-dependent, neutral proteases, active in the cells responding to signals inducing a rise of cytoplasmic Ca(++)) is involved in the regulation of apoptosis of some cell types by interaction with caspase-3. This work verifies the hypothesis of the abnormal activity of calpains and its role in reduced apoptosis of the B-CLL cells. Casein zymography, reverse transcriptase-polymerase chain reaction, and Western blotting were used for identification and quantification of the activity and expression of calpains in B-CLL cells and purified normal B lymphocytes. The activity and expression of mu-calpain (requiring micromolar Ca(++) for activation) are significantly higher in the leukemic than in nonmalignant cells. Contrarily, the activity and expression of m-calpain (requiring millimolar Ca(++)) as well as the expression of calpastatin (an endogenous inhibitor of calpains) are unchanged or reduced in the B-CLL lymphocytes. Correspondingly, the activity of caspase-3 is many times lower in the B-CLL cells than in normal B lymphocytes. Inhibition of overexpressed mu-calpain in living B-CLL cells in vitro results in doubling of the proportion of the cells undergoing spontaneous apoptosis. This observation suggests a possible role for calpains in longer survival of the B-CLL cells and may open new therapeutic possibilities.
Witkowski
Jacek M
JM
Department of Pathophysiology, Medical University of Gdansk, Poland. jawit@amedec.amg.gda.pl
Zmuda-Trzebiatowska
Emilia
E
Swiercz
Jakub M
JM
Cichorek
Miroslawa
M
Ciepluch
Hanna
H
Lewandowski
Krzysztof
K
Bryl
Ewa
E
Hellmann
Andrzej
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D017252:CD3 Complex; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015398:Signal Transduction
D017252:CD3 Complex; D002154:Calpain; D002118:Calcium