Laitinen J T, Uri A, Raidaru G, Miettinen R
Department of Physiology, University of Kuopio, Finland Institute of Chemical Physics, Tartu University, Estonia Department of Neuroscience and Neurology, University and University Hospital of Kuopio, Finland.
J Neurochem. 2001 Apr;77(2):505-18. doi: 10.1046/j.1471-4159.2001.00265.x.
No G(i)-linked P2Y receptors have been cloned to date but the presence of such receptors is thought to be restricted to platelets and certain clonal cell lines. Using the functional approach of [(35)S]guanosine 5'-[gamma-thio]-triphosphate autoradiography, we uncovered the widespread presence of such receptors in the CNS. Under conditions in which the prominent signal due to tonic adenosine receptor activity is masked, ADP and ATP stimulated G-protein activity in multiple grey and white matter regions. Localization in the grey matter suggests inhibitory auto-/heteroreceptor function. In the white matter, activated G proteins appeared as 'hot spots' (presumed oligodendrocyte progenitors) with scattered distribution along the main fibre tracts. Responses to ATP were diminished under conditions that inhibited degradation, suggesting that prior conversion to ADP explained agonist action. Uracil nucleotides were ineffective but 2-methylthio-ADP activated G proteins approximately 500-fold more potently than ADP, although both were similarly degraded. Throughout the brain, ADP-dependent G-protein activity was reversed by 2-hexylthio-AdoOC(O)Asp(2), a non-phosphate ATP analogue, whereas selective P2Y(1) receptor antagonists proved ineffective. A similar receptor was also disclosed from the adrenal medulla. These data witness a hitherto unrecognized abundance of G(i/o)-linked ADP receptors in the nervous system. Biochemical and pharmacological behaviour suggests striking similarities to the elusive platelet P2Y(ADP) receptor.
迄今为止，尚未克隆出与G(i)偶联的P2Y受体，但此类受体被认为仅存在于血小板和某些克隆细胞系中。我们采用[³⁵S]鸟苷5'-[γ-硫代]三磷酸放射自显影的功能研究方法，发现此类受体在中枢神经系统中广泛存在。在强直腺苷受体活性产生的显著信号被掩盖的条件下，ADP和ATP可刺激多个灰质和白质区域的G蛋白活性。灰质中的定位表明其具有抑制性自身/异源受体功能。在白质中，活化的G蛋白表现为“热点”（推测为少突胶质细胞前体细胞），沿主要纤维束呈散在分布。在抑制降解的条件下，对ATP的反应减弱，这表明先前转化为ADP可解释激动剂的作用。尿嘧啶核苷酸无效，但2-甲硫基-ADP激活G蛋白的效力比ADP高约500倍，尽管二者降解情况相似。在整个大脑中，2-己硫基-AdoOC(O)Asp(2)（一种非磷酸ATP类似物）可逆转依赖ADP的G蛋白活性，而选择性P2Y(1)受体拮抗剂则无效。在肾上腺髓质中也发现了类似的受体。这些数据证明神经系统中存在迄今未被认识到的大量与G(i/o)偶联的ADP受体。生化和药理学行为表明，其与难以捉摸的血小板P2Y(ADP)受体有显著相似之处。
