Inhibition of natural killer cell-mediated cytotoxicity by ML-9, a selective inhibitor of myosin light chain kinase.
To investigate the role of microfilaments in natural killer (NK) cell-mediated cytotoxicity, general microfilament inhibitors, cytochalasins B,D and dihydrocytochalasin B, and a selective inhibitor of myosin light chain kinase (MLCK) which regulates microfilament contraction, i.e. 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) were examined in an NK assay system. ML-9 inhibited NK cell activity in a dose-dependent manner without affecting target cell binding, whereas cytochalasins suppressed the binding. The dextran suspension method revealed that ML-9 inhibits the programming for the lysis stage of the lytic process. In the single cell assay, the addition of ML-9 after target cell binding had occurred inhibited the lysis of bound target cells, whereas the addition of cytochalasins in a similar manner did not affect it. Thus, these results suggest the possibility that microfilament contraction is involved in the lytic mechanism of NK cell-mediated cytolysis. However, the mechanism whereby cytochalasins inhibit target cell binding remains unclear.
Ito
M
M
Department of Bacteriology, Fukushima Medical College, Japan.
Tanabe
F
F
Sato
A
A
Ishida
E
E
Takami
Y
Y
Shigeta
S
S
D008841:Actin Cytoskeleton / Q000502:physiology; D001381:Azepines / Q000494:pharmacology*; D003572:Cytochalasins / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D010766:Phosphorylation
D001381:Azepines; D003572:Cytochalasins; C056218:ML 9; D009219:Myosin-Light-Chain Kinase