Inhibiting myosin light chain kinase induces apoptosis in vitro and in vivo.
Previous short-term studies have correlated an increase in the phosphorylation of the 20-kDa light chain of myosin II (MLC20) with blebbing in apoptotic cells. We have found that this increase in MLC20 phosphorylation is rapidly followed by MLC20 dephosphorylation when cells are stimulated with various apoptotic agents. MLC20 dephosphorylation is not a consequence of apoptosis because MLC20 dephosphorylation precedes caspase activation when cells are stimulated with a proapoptotic agent or when myosin light chain kinase (MLCK) is inhibited pharmacologically or by microinjecting an inhibitory antibody to MLCK. Moreover, blocking caspase activation increased cell survival when MLCK is inhibited or when cells are treated with tumor necrosis factor alpha. Depolymerizing actin filaments or detaching cells, processes that destabilize the cytoskeleton, or inhibiting myosin ATPase activity also resulted in MLC20 dephosphorylation and cell death. In vivo experiments showed that inhibiting MLCK increased the number of apoptotic cells and retarded the growth of mammary cancer cells in mice. Thus, MLC20 dephosphorylation occurs during physiological cell death and prolonged MLC20 dephosphorylation can trigger apoptosis.
Department of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois 60612, USA.
Fabeha
F
Fazal
Lianzhi
L
Gu
Ivanna
I
Ihnatovych
Yoojeong
Y
Han
WenYang
W
Hu
Nenad
N
Antic
Fernando
F
Carreira
James F
JF
Blomquist
Thomas J
TJ
Hope
David S
DS
Ucker
Primal
P
de Lanerolle
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D051379:Mice; D018994:Myosin Light Chains / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors* / Q000276:immunology; D010766:Phosphorylation
D000906:Antibodies; D061945:Caspase Inhibitors; D018994:Myosin Light Chains; D009219:Myosin-Light-Chain Kinase; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D024462:Myosin Type II