Liberini Claudia G, Boyle Christina N, Cifani Carlo, Venniro Marco, Hope Bruce T, Lutz Thomas A
Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zürich (UZH), Winterthurerstrasse 260, CH-8057, Zürich, Switzerland.
Zürich Centre for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland.
Eur J Neurosci. 2016 Mar;43(5):653-61. doi: 10.1111/ejn.13163. Epub 2016 Feb 5.
Amylin is a pancreatic β-cell hormone that acts as a satiating signal to inhibit food intake by binding to amylin receptors (AMYs) and activating a specific neuronal population in the area postrema (AP). AMYs are heterodimers that include a calcitonin receptor (CTR) subunit [CTR isoform a or b (CTRa or CTRb)] and a member of the receptor activity-modifying proteins (RAMPs). Here, we used single-cell quantitative polymerase chain reaction to assess co-expression of AMY subunits in AP neurons from rats that were injected with amylin or vehicle. Because amylin interacts synergistically with the adipokine leptin to reduce body weight, we also assessed the co-expression of AMY and the leptin receptor isoform b (LepRb) in amylin-activated AP neurons. Single cells were collected from Wistar rats and from transgenic Fos-GFP rats that express green fluorescent protein (GFP) under the control of the Fos promoter. We found that the mRNAs of CTRa, RAMP1, RAMP2 and RAMP3 were all co-expressed in single AP neurons. Moreover, most of the CTRa+ cells co-expressed more than one of the RAMPs. Amylin down-regulated RAMP1 and RAMP3 but not CTR mRNAs in AMY+ neurons, suggesting a possible negative feedback mechanism of amylin at its own primary receptors. Interestingly, amylin up-regulated RAMP2 mRNA. We also found that a high percentage of single cells that co-expressed all components of a functional AMY expressed LepRb mRNA. Thus, single AP cells expressed both AMY and LepRb, which formed a population of first-order neurons that presumably can be directly activated by amylin and, at least in part, also by leptin.
胰淀素是一种胰腺β细胞激素，它作为一种饱腹感信号，通过与胰淀素受体（AMYs）结合并激活最后区（AP）的特定神经元群体来抑制食物摄入。AMYs是异源二聚体，包括一个降钙素受体（CTR）亚基[CTR同工型a或b（CTRa或CTRb）]和受体活性修饰蛋白（RAMPs）成员。在这里，我们使用单细胞定量聚合酶链反应来评估注射胰淀素或赋形剂的大鼠AP神经元中AMY亚基的共表达。由于胰淀素与脂肪因子瘦素协同作用以减轻体重，我们还评估了胰淀素激活的AP神经元中AMY与瘦素受体同工型b（LepRb）的共表达。从Wistar大鼠和在Fos启动子控制下表达绿色荧光蛋白（GFP）的转基因Fos-GFP大鼠中收集单细胞。我们发现CTRa、RAMP1、RAMP2和RAMP3的mRNA均在单个AP神经元中共表达。此外，大多数CTRa+细胞共表达不止一种RAMP。胰淀素下调了AMY+神经元中的RAMP1和RAMP3，但未下调CTR mRNA，提示胰淀素在其自身主要受体处可能存在负反馈机制。有趣的是，胰淀素上调了RAMP2 mRNA。我们还发现，共表达功能性AMY所有成分的单细胞中有很高比例表达LepRb mRNA。因此，单个AP细胞同时表达AMY和LepRb，形成了一群一级神经元，推测它们可能直接被胰淀素激活，至少部分也可被瘦素激活。
