Selective activation by atrial natriuretic factor of phosphatidylcholine-specific phospholipase activities in purified heart muscle plasma membranes.
We have characterized a membrane-bound phosphatidylcholine (PC) specific phospholipase C (PC-PLC) in plasma membranes from rat cardiac muscle, and have investigated the role of PC-PLC and PC-specific phospholipase D (PC-PLD) activities in the mechanism of action of atrial natriuretic factor (ANF). In purified sarcolemma, ANF stimulated over a wide range of concentrations with a maximum at 10(-11) M the hydrolysis of phosphatidylcholine through PC-PLD giving phosphatidate and choline, whereas higher concentrations of ANF (10(-10) M) preferentially stimulated PC breakdown through PC-PLC to form diacylglycerol and phosphocholine. To confirm the involvement of the PC-PLD in the mechanism of ANF action, we measured the transphosphatidylation reaction, a specific assay for this phospholipase which in the presence of ethanol catalyses the phosphatidylethanol formation from PC. ANF stimulated phosphatidylethanol formation with the same dose-response behavior as phosphatidate formation. The significant diacylglycerol increase at 10(-10) M ANF, in the presence of propranolol, a potent inhibitor of phosphatidate phosphatase which can hydrolyse phosphatidate to give diacylglycerol, suggested a direct involvement of PC-PLC. The use of GTP-gamma-S, a non hydrolysable analog of GTP, and of pertussis toxin showed the involvement of a pertussis toxin insensitive G protein in PC-PLC mediated ANF signal transduction. We suggest a differential effect of ANF on PC breakdown by phospholipases C and D depending on the concentration of the peptide.
Baldini
P M
PM
Department of Biology, University of Rome Tor Vergata, Italy.
Incerpi
S
S
Zannetti
A
A
De Vito
P
P
Luly
P
P
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D015415:Biomarkers / Q000737:chemistry; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D006321:Heart / Q000187:drug effects*; D006868:Hydrolysis; D008297:Male; D009206:Myocardium / Q000201:enzymology; D010713:Phosphatidylcholines / Q000378:metabolism*; D010740:Phospholipases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000032:analysis
D015415:Biomarkers; D010713:Phosphatidylcholines; D009320:Atrial Natriuretic Factor; D010740:Phospholipases; D010738:Type C Phospholipases