[The role of a GTP-binding protein in coupling of a muscarinic cholinergic receptor and Na,K-ATPase in myocardial sarcolemma].
The effects of the cholinergic agonist carbachol (Cch) and guanine nucleotides on the Na,K-ATPase and K-dependent p-nitrophenylphosphatase (K-p-NPPase) activities in rabbit and dog myocardial sarcolemma vesicles in the presence of the pore-forming antibiotic alamethicin (20 micrograms/ml), was studied. Cch (0.01-100 microM) inhibited the both enzymatic activities by 40-45% (IC50 = 0.3-0.5 microM) only after addition of GTP (50 microM) or its analogs: GTP gamma S (0.1-1.0 microM) and Gpp(NH)p (10 microM). The muscarinic acetylcholine receptor (mAchR) antagonist atropine (10 microM) blocked the effect of Cch. GTP gamma S alone produced a concentration-dependent decrease in the both Na,K-ATPase and K-p-NPPase activities by 40-45% (IC50 = 1-2 microM) with a lag period of about 3 minutes; this lag disappeared in the presence of the agonist. The GDP analog GDP beta S (0.01-100 microM) neither affected these activities nor promoted the inhibiting effect of Cch. Pretreatment of sarcolemmal vesicles with 20 micrograms/ml of pertussis toxin in the presence of 100 microM NAD abolished the inhibiting effect of Cch on the Na,K-ATPase and phosphatase activities. Under these conditions pertussis toxin catalyzed the ADP-ribosylation of alpha-subunits of the inhibitory GTP-binding protein (G1) which were identified immunochemically as alpha i2, alpha i3 and, possibly, alpha i1. The data obtained testify to the involvement of G1 in the mAchR-mediated inhibition of myocardial sarcolemmal Na,K-ATPase as well as in the signal transduction from the receptor to the enzyme.
Turmukhambetova
V K
VK
Danilenko
M P
MP
Panchenko
M P
MP
Ritov
V B
VB
Esyrev
O V
OV
Tkachuk
V A
VA
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000502:physiology*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D037342:Pertussis Toxin; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012508:Sarcolemma / Q000201:enzymology / Q000378:metabolism*; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D011976:Receptors, Muscarinic; D010566:Virulence Factors, Bordetella; D001285:Atropine; D002217:Carbachol; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000254:Sodium-Potassium-Exchanging ATPase
Rol' GTP-sviazyvaiushchego belka v sopriazhenii muskarinovogo kholinoretseptora i Na,K-ATPase v sarkolemme miokarda.