Filippov A K, Brown D A
Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Eur J Neurosci. 1996 Jun;8(6):1149-55. doi: 10.1111/j.1460-9568.1996.tb01282.x.
A P2U (UTP-sensitive) nucleotide receptor has previously been cloned from NG108-15 neuroblastoma x glioma hybrid cells and it has been shown that activation of this receptor inhibits the M-type K+-current. We now report that UTP also inhibits Ca2+-currents in differentiated NG108-15 cells, but probably through a different nucleotide receptor. UTP (100 microM) inhibited the peak of the high-threshold current by 28.4 +/- 3.1% (n = 28) with no effect on the low-threshold current. Two components of high-threshold current were identified: one inhibited by 100 nM omega-conotoxin (CgTx) and one inhibited by 2 microM nifedipine and enhanced by 1 microM BAY K8644. UTP inhibited the former by 31.0 +/- 3.1%, with an IC50 of 2. 8 +/- 1.1 microM, and the latter 34.2 +/- 6.1% with an IC50 of 1.7 +/- 1.3 microM. Pertussis toxin pretreatment prevented inhibition of the CgTx-sensitive, nifedipine-resistant but not CgTx-resistant current. Inhibition was not prevented by intracellular BAPTA (20 mM) or cAMP (1mM). Effects of UTP on both currents were imitated by UDP, ATP, ADP, AP4A and ATPgammaS but weakly or not at all by 2-MeSATP, GTP, AMP-CPP or ITP. Since the receptors which inhibit Ca2+-currents are activated by ATP, it is suggested that they might mediate auto-inhibition of transmitter release by ATP if present on purinergic nerve terminals.
nucleotides, UTP, ATP, calcium currents, neuroblastoma cells
先前已从NG108 - 15神经母细胞瘤×胶质瘤杂交细胞中克隆出一种P2U（对UTP敏感）核苷酸受体，并且已表明该受体的激活会抑制M型钾电流。我们现在报告，UTP也会抑制分化的NG108 - 15细胞中的钙电流，但可能是通过一种不同的核苷酸受体。UTP（100微摩尔）使高阈值电流的峰值抑制了28.4±3.1%（n = 28），而对低阈值电流没有影响。鉴定出高阈值电流的两个成分：一个被100纳摩尔的ω - 芋螺毒素（CgTx）抑制，另一个被2微摩尔硝苯地平抑制并被1微摩尔BAY K8644增强。UTP使前者抑制了31.0±3.1%，IC50为2.8±1.1微摩尔，使后者抑制了34.2±6.1%，IC50为1.7±1.3微摩尔。百日咳毒素预处理可防止对CgTx敏感、硝苯地平耐药电流的抑制，但不能防止对CgTx耐药电流的抑制。细胞内BAPTA（20毫摩尔）或cAMP（1毫摩尔）不能防止抑制作用。UTP对两种电流的作用可被UDP、ATP、ADP、AP4A和ATPγS模拟，但被2 - MeSATP、GTP、AMP - CPP或ITP微弱模拟或完全不模拟。由于抑制钙电流的受体可被ATP激活，因此提示如果存在于嘌呤能神经末梢，它们可能介导ATP对递质释放的自身抑制。
核苷酸；UTP；ATP；钙电流；神经母细胞瘤细胞
