Oxytocin stimulation of RGS2 mRNA expression in cultured human myometrial cells.
Regulators of G protein signaling (RGS proteins) interact with Galpha(q) and Galpha(i) and accelerate GTPase activity. These proteins have been characterized only within the past few years, so our understanding of their importance is still preliminary. We examined the effect of oxytocin on RGS2 mRNA expression to help determine the role of RGS proteins in oxytocin signaling in human myometrial cells in primary culture. Oxytocin increased RGS2 mRNA concentration maximally by 1 or 2 h in a dose-dependent and agonist-specific manner. RGS2 mRNA levels were also elevated by treatment with Ca(2+) ionophore, phorbol ester, or forskolin. Oxytocin's effects were completely inhibited by an intracellular Ca(2+) chelator and partially blocked by a protein kinase C inhibitor, indicating that intracellular Ca(2+) concentration is the primary signal for oxytocin elevation of RGS2 mRNA levels. Use of pharmacological inhibitors indicated that part of oxytocin-stimulated RGS2 mRNA expression is mediated by G(i)/tyrosine kinase activities. Although oxytocin does not stimulate increases in intracellular cAMP concentration, agents that elevate intracellular cAMP concentrations and cause myometrial relaxation may possibly cause heterologous desensitization to oxytocin via RGS2 expression. These results suggest that RGS2 may be important in regulating the myometrial response to oxytocin.
Park
Eun Sung
ES
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas 77555-1062, USA.
Echetebu
Clement O
CO
Soloff
Solweig
S
Soloff
Melvyn S
MS
D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004357:Drug Synergism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D009215:Myometrium / Q000378:metabolism*; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D011493:Protein Kinase C / Q000378:metabolism; D020710:RGS Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007295:Inositol Phosphates; D007476:Ionophores; D020710:RGS Proteins; D012333:RNA, Messenger; C105345:Rgs2 protein, mouse; D010566:Virulence Factors, Bordetella; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D005576:Colforsin; D000001:Calcimycin; D010121:Oxytocin; D004533:Egtazic Acid; D000242:Cyclic AMP; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D013755:Tetradecanoylphorbol Acetate