Nicholas R A, Watt W C, Lazarowski E R, Li Q, Harden K
Department of Pharmacology, University of North Carolina, School of Medicine, Chapel Hill 27599-7365, USA.
Mol Pharmacol. 1996 Aug;50(2):224-9.
Observation that the G protein-coupled P2U receptor (P2Y2 receptor) is activated by UTP as well as ATP provided the first indication that a class of uridine nucleotide-responsive receptors might exist. This hypothesis was confirmed by our identification of a uridine nucleotide-specific receptor on C6-2B rat glioma cells and by the recent cloning of two uridine nucleotide-responsive receptors, the P2Y6 receptor [J. Biol. Chem. 270:26152-26158 (1995)] and the P2Y4 receptor [J. Biol. Chem. 270:30849-30852 (1995) and J. Biol. Chem. 270:30845-30848 (1995)]. The relative nucleotide selectivities of these uridine nucleotide-activated receptors have not been established. Therefore, we cloned and expressed the P2Y6 and P2Y4 receptors in 1321N1 human astrocytoma cells and compared their relative selectivities for UDP, UTP, and other uridine and adenine nucleotides with that of the P2Y2 receptor expressed in the same cells. These comparisons were made by measuring inositol phosphate accumulation under conditions in which the initial purity and stability of agonists were rigidly ensured and quantitatively assessed. The data indicate that the P2Y2 receptor is activated with similar potencies by ATP and UTP but not by ADP or UDP; the P2Y6 receptor is activated most potently by UDP but weakly by UTP, ATP, and ADP; and the P2Y4 receptor is activated most potently by UTP, less potently by ATP, and not at all by nucleotide diphosphates. Furthermore, the P2Y6 receptor, which displays a uridine nucleotide selectivity essentially identical to that of the uridine nucleotide-specific receptor in C6-2B cells, was shown to be natively expressed in C6-2B cells and to account for the uridine nucleotide responses originally identified in these cells. These results define the uridine nucleotide selectivity of three phospholipase C-linked receptors: a receptor that is selectively activated by UDP (P2Y6 receptor), selectively activated by UTP (P2Y4 receptor), and activated by UTP and ATP but not by diphosphate nucleotides (P2Y2 receptor).
观察发现G蛋白偶联的P2U受体（P2Y2受体）可被UTP以及ATP激活，这首次表明可能存在一类尿苷酸反应性受体。我们在C6 - 2B大鼠胶质瘤细胞上鉴定出一种尿苷酸特异性受体，以及最近克隆出两种尿苷酸反应性受体，即P2Y6受体[《生物化学杂志》270:26152 - 26158(1995)]和P2Y4受体[《生物化学杂志》270:30849 - 30852(1995)以及《生物化学杂志》270:30845 - 30848(1995)]，从而证实了这一假说。这些尿苷酸激活受体的相对核苷酸选择性尚未确定。因此，我们在1321N1人星形细胞瘤细胞中克隆并表达了P2Y6和P2Y4受体，并将它们对UDP、UTP以及其他尿苷和腺嘌呤核苷酸的相对选择性与同一细胞中表达的P2Y2受体进行了比较。这些比较是在严格确保激动剂初始纯度和稳定性并进行定量评估的条件下，通过测量肌醇磷酸积累来进行的。数据表明，P2Y2受体被ATP和UTP以相似的效力激活，但不被ADP或UDP激活；P2Y6受体被UDP激活的效力最强，被UTP、ATP和ADP激活的效力较弱；P2Y4受体被UTP激活的效力最强，被ATP激活的效力较弱，且不被二磷酸核苷酸激活。此外，P2Y6受体在C6 - 2B细胞中天然表达，其尿苷酸选择性与C6 - 2B细胞中的尿苷酸特异性受体基本相同，并且是这些细胞中最初鉴定出的尿苷酸反应的原因。这些结果确定了三种与磷脂酶C相关的受体的尿苷酸选择性：一种被UDP选择性激活的受体（P2Y6受体）、被UTP选择性激活的受体（P2Y4受体）以及被UTP和ATP激活但不被二磷酸核苷酸激活的受体（P2Y2受体）。
