Candidate inhibitor of the volume-sensitive kinase regulating K-Cl cotransport: the myosin light chain kinase inhibitor ML-7.
K-Cl cotransport, KCC, is activated by swelling in many cells types, and promotes volume regulation by a KCl efflux osmotically coupled to water efflux. KCC is probably activated by swelling-inhibition of a kinase, permitting dephosphorylation, and activation of the cotransporter by a phosphatase. The myosin light chain kinase (MLCK) inhibitor ML-7 inhibits transporters activated by shrinkage. In red blood cells from three mammalian species, ML-7 stimulated KCC in a volume-dependent manner. Relative stimulation was greatest in more shrunken cells. Stimulation was reduced by moderate cell swelling and abolished by further swelling. The half-maximal stimulation is at approximately 20 microm ML-7, 50-fold greater than the IC(50) for inhibition of MLCK in vitro. Stimulation of KCC by ML-7 did not require cell Ca, while MLCK does. Therefore the target of ML-7 in stimulating KCC in red cells is probably not MLCK. The evidence favors stimulation of KCC by ML-7 by inhibiting the volume-sensitive kinase. Qualitatively similar effects of ML-7 on KCC in red cells from three mammalian species suggest a general mechanism.
Kelley
S J
SJ
Department of Biology, Syracuse University, Syracuse, NY 13244, USA.
Thomas
R
R
Dunham
P B
PB
D000328:Adult; D000470:Alkaloids / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002227:Carbazoles; D002352:Carrier Proteins / Q000378:metabolism*; D048429:Cell Size; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007211:Indoles; D008274:Magnesium / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D009281:Naphthalenes / Q000494:pharmacology*; D012756:Sheep; D019311:Staurosporine / Q000494:pharmacology; D027981:Symporters; D000077191:Wortmannin; D000096922:K Cl- Cotransporters
D000470:Alkaloids; D000730:Androstadienes; D001381:Azepines; D000001:Calcimycin; D002118:Calcium; D002227:Carbazoles; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007211:Indoles; D008274:Magnesium; D009219:Myosin-Light-Chain Kinase; D009281:Naphthalenes; D019311:Staurosporine; D027981:Symporters; D000077191:Wortmannin; D000096922:K Cl- Cotransporters; C119650:SLC12A6 protein, human; C056218:ML 9; C070571:ML 7; C063769:KT 5926