Functional Compensation between Cholecystokinin-1 and -2 Receptors in Murine Paraventricular Nucleus Neurons*
Functional Compensation between Cholecystokinin-1 and -2 Receptors in Murine Paraventricular Nucleus Neurons*
复制标题
DOI：
10.1074/jbc.m112.416214
复制
发表时间：
2012-10
期刊：
影响因子：
--
通讯作者：
Shahid Mohammad;Tomoya Ozaki;Kouhei Takeuchi;K. Unno;Kurumi Yamoto;Eri Morioka;S. Takiguchi;M. Ikeda
中科院分区：
文献类型：
--
作者：
Shahid Mohammad;Tomoya Ozaki;Kouhei Takeuchi;K. Unno;Kurumi Yamoto;Eri Morioka;S. Takiguchi;M. Ikeda
背景：胆囊收缩素（CCK）-1受体配体控制饱腹感。然而，受体基因敲除小鼠的正常摄入行为对CCK介导的饱腹感控制提出了质疑。结果如下：CCK-1受体基因敲除促进了室旁后核CCK-2受体信号传导，并转换了负责饱腹感控制的受体亚型。结论：CCK-1和CCK-2受体之间的协同作用保证了正常的摄入。意义：代偿性受体功能揭示了CCK介导的饱腹感控制机制。胆囊收缩素（CCK）及其受体亚型CCK-1和CCK-2具有多种稳态功能。CCK-1和CCK-2受体共享一个共同的磷脂酰肌醇信号通路，但很少有人知道他们可能的功能耦合。我们专注于CCK介导的Ca 2+信号在小细胞室旁核（PVN）细胞，控制饱腹感和其他自主神经功能。对小鼠下丘脑切片的分析表明，一般CCK受体激动剂CCK-8 s（10 nm）触发的Ca 2+瞬变最显着的PVN（PaPo）的后亚区。这种10 nm CCK-8 s诱导的反应在CCK-1受体敲除（CCK 1 R-/-）切片中不存在，表明该反应是由CCK-1受体介导的。CCK-8 s浓度高于30 nm时，野生型和CCK 1 R −/−切片中的Ca 2+升高相似。CCK-8 s（100 nm）诱导的CCK 1 R −/−脑片中的大Ca 2+响应可被CCK-2受体拮抗剂（CI-988）阻断，而野生型脑片中的大Ca 2+响应需要CI-988和lorglumide（CCK-1受体拮抗剂）的混合物才能完全拮抗。因此，CCK-1和-2受体可能在单个PaPo神经元中协同作用，并且CCK-1受体的缺失可能促进CCK-2受体信号传导。这一假设得到了实时RT-PCR、免疫荧光双标记和Western印迹分析结果的支持，这些结果表明CCK-2受体在CCK 1 R −/−小鼠的PaPo神经元中过表达。此外，行为研究表明，腹腔注射lorglumide上调野生型小鼠的食物获取，但在CCK 1 R −/−小鼠中没有，而CI-988注射上调CCK 1 R −/−小鼠的食物获取，但在野生型小鼠中没有。在CCK 1 R −/−小鼠中通过CCK-2受体的补偿性CCK信号传导揭示了目前有争议的饱腹感控制机制。
Background: Cholecystokinin (CCK)-1 receptor ligands control satiety. Normal intake behaviors in the receptor gene knock-out mice, however, raise questions for CCK-mediated satiety control. Results: CCK-1 receptor gene knock-out facilitated CCK-2 receptor signaling in the posterior paraventricular nucleus and switched receptor subtypes responsible for satiety control. Conclusion: Synergic interaction between CCK-1 and -2 receptors guarantees regular intakes. Significance: Compensatory receptor functions shed light on CCK-mediated satiety controlling mechanism. Cholecystokinin (CCK) and its receptor subtypes CCK-1 and -2 have diverse homeostatic functions. CCK-1 and -2 receptors share a common phosphatidylinositol signaling pathway, yet little is known regarding their possible functional coupling. We focused on CCK-mediated Ca2+ signaling in parvocellular paraventricular nucleus (PVN) cells, which control satiety and other autonomic functions. Analysis of mouse hypothalamic slices demonstrated that the general CCK receptor agonist CCK-8s (10 nm) triggered Ca2+ transients most significantly in the posterior subregion of the PVN (PaPo). This 10 nm CCK-8s-induced response was absent in CCK-1 receptor knock-out (CCK1R−/−) slices, showing that the response is mediated by CCK-1 receptors. CCK-8s concentrations higher than 30 nm triggered a Ca2+ rise similarly in wild-type and CCK1R−/− slices. The large CCK-8s (100 nm)-induced Ca2+ responses in CCK1R−/− slices were blocked by a CCK-2 receptor antagonist (CI-988), whereas those in wild-type slices required a mixture of CI-988 and lorglumide (a CCK-1 receptor antagonist) for complete antagonism. Therefore, CCK-1 and -2 receptors may function synergistically in single PaPo neurons and deletion of CCK-1 receptors may facilitate CCK-2 receptor signaling. This hypothesis was supported by results of real-time RT-PCR, immunofluorescence double labeling and Western blotting assays, which indicated CCK-2 receptor overexpression in PaPo neurons of CCK1R−/− mice. Furthermore, behavioral studies showed that intraperitoneal injections of lorglumide up-regulated food accesses in wild-type but not in CCK1R−/− mice, whereas CI-988 injections up-regulated food accesses in CCK1R−/− but not in wild-type mice. Compensatory CCK signaling via CCK-2 receptors in CCK1R−/− mice shed light on currently controversial satiety-controlling mechanisms.