Phospholipase C-delta1 and oxytocin receptor signalling: evidence of its role as an effector.
Although the oxytocin receptor modulates intracellular Ca2+ ion levels in myometrium, the identities of signal molecules have not been clearly clarified. Our previous studies on oxytocin receptor signalling demonstrated that 80 kDa Ghalpha is a signal mediator [Baek, Kwon, Lee, Kim, Muralidhar and Im (1996) Biochem. J. 315, 739-744]. To elucidate the effector in the oxytocin receptor signalling pathway, we evaluated the oxytocin-mediated activation of phospholipase C (PLC) by using solubilized membranes from human myometrium and a three-component preparation containing the oxytocin receptor-Ghalpha-PLC-delta1 complex. PLC-delta1 activity in the three-component preparation, as well as PLC activity in solubilized membranes, was increased by oxytocin in the presence of Ca2+ and activated Ghalpha (GTP-bound Ghalpha). Furthermore the stimulated PLC-delta1 activity resulting from activation of Ghalpha via the oxytocin receptor was significantly attenuated by the selective oxytocin antagonist desGly-NH2d(CH2)5[Tyr(Me)2,Thr4]ornithine vasotocin or GDP. Consistent with these observations, co-immunoprecipitation and co-immunoadsorption of PLC-delta1 in the three-component preparation by anti-Gh7alpha antibody resulted in the PLC-delta1 being tightly coupled to activated Ghalpha on stimulation of the oxytocin receptor. These results indicate that PLC-delta1 is the effector for Ghalpha-mediated oxytocin receptor signalling.
Park
E S
ES
Department of Biochemistry, College of Medicine, Chung-Ang University, 221 Heuksuk-Dong, Dongjak-Gu, Seoul 156-756, South Korea.
Won
J H
JH
Han
K J
KJ
Suh
P G
PG
Ryu
S H
SH
Lee
H S
HS
Yun
H Y
HY
Kwon
N S
NS
Baek
K J
KJ
D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism* / Q000494:pharmacology; D054803:Phospholipase C delta; D018045:Receptors, Oxytocin / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism*
D007527:Isoenzymes; D018045:Receptors, Oxytocin; D010121:Oxytocin; D010738:Type C Phospholipases; C518024:PLCD1 protein, human; D054803:Phospholipase C delta; D002118:Calcium