Adenosine triphosphate activates mitogen-activated protein kinase in humangranulosa-luteal cells

ATP has been shown to activate the phospholipase C/diacylglycerol/protein k inase C (PKC) pathway. However, little is known about the downstream signal ing events. The present study was designed to examine the effect of ATP on activation of the mitogen-activated protein kinase (MAPK) signaling pathway and its physiological role in human granulosa-luteal cells. Western blot a nalysis, using a monoclonal antibody that detected the phosphorylated forms of extracellular signal-regulated kinase-l and -2 (p42(mapk) and p44 (mapk ) respectively), demonstrated that ATP activated MAPK in a dose- and time-d ependent manner. Treatment of the cells with suramin (a P2 purinoceptor ant agonist), neomycin (a phospholipase C inhibitor), staurosporin (a PKC inhib itor), or PD98059 (an MAPK/ERK kinase inhibitor) significantly attenuated t he ATP-induced activation of MAPK. In contrast, ATP-induced MAPK activation was not significantly affected by pertussis toxin (a G, inhibitor). To exa mine the role of G, protein, the intracellular cAMP level was determined af ter treatment with ATP or hCG. No significant elevation of intracellular cA MP was noted after ATP treatment. To determine the role of MAPK in steroido genesis, human granulosa-luteal cells were treated with ATP, hCG, or ATP pl us hCG in the presence or absence of PD98059. RLA revealed that ATP alone d id not significantly affect the basal progesterone concentration. However, hCG-induced progesterone production was reduced by ATP treatment. PD98059 r eversed the inhibitory effect of ATP on hCG-induced progesterone production . To our knowledge, this is the first demonstration of ATP-induced activati on of the MAPK signaling pathway in the human ovary. These results support the idea that the MAPK signaling pathway is involved in mediating ATP actio ns in the human ovary.