Coupling of L-type voltage-sensitive calcium channels to P2X(2) purinoceptors in PC-12 cells.
Extracellular ATP elevates cytosolic Ca(2+) by activating P2X and P2Y purinoceptors and voltage-sensitive Ca(2+) channels (VCCCs) in PC-12 cells, thereby facilitating catecholamine secretion. We investigated the mechanism by which ATP activates VSCCs. 2-Methylthioadenosine 5'-triphosphate (2-MeS-ATP) and UTP were used as preferential activators of P2X and P2Y, respectively. Nifedipine inhibited the ATP- and 2-MeS-ATP-evoked cytosolic Ca(2+) concentration increase and [(3)H]norepinephrine secretion, but not the UTP-evoked responses. Studies with Ca(2+) channel blockers indicated that L-type VSCCs were activated after the P2X activation. Mn(2+) entry profiles and studies with thapsigargin revealed that Ca(2+) entry, rather than Ca(2+) release, was sensitive to nifedipine. Although P2X(2) and P2X(4) receptor mRNAs were detected, studies with pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid revealed that P2X(2) was mainly coupled to the L-type VSCCs. The inhibitory effect of nifedipine did not occur in the absence of extracellular Na(+), suggesting that Na(+) influx, which induces depolarization, was essential for the P2X(2)-mediated activation of VSCCs. We report that depolarization induced by Na(+) entry through the P2X(2) purinoceptors effectively activates L-type VSCCs in PC-12 cells.
Hur
E M
EM
Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea.
Park
T J
TJ
Kim
K T
KT
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D016716:PC12 Cells; D020033:Protein Isoforms / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D058476:Receptors, Purinergic P2X2; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020033:Protein Isoforms; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D013873:Thionucleotides; D008345:Manganese; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D020866:omega-Conotoxin GVIA; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium; D014544:Uridine Triphosphate; D009638:Norepinephrine; C008501:2-methylthio-ATP