Breivogel Chris S, McPartland John M, Parekh Bhavita
a Department of Pharmaceutical Sciences , Campbell University College of Pharmacy & Health Sciences , Buies Creek , NC , USA.
b College of Medicine, University of Vermont , Burlington , VT , USA.
J Recept Signal Transduct Res. 2018 Aug;38(4):316-326. doi: 10.1080/10799893.2018.1494743. Epub 2018 Oct 31.
Previous studies have found non-CB non-CB G-protein-coupled receptors in rodents that are activated by the aminoalkylindole cannabinoid agonist WIN55212-2. This work obtained evidence for the presence or absence of similar receptors in the brains of other mammals, birds and amphibians.
Antagonism of the stimulation of [S]GTPγS binding by WIN55212-2 and CP55940 was assessed in multiple CNS regions of rat and canine, and in whole brain membranes from shrew, pigeon, frog and newt. A bioinformatics approach searched for orthologs of GRP3, GPR6, and GPR12 (closely related to cannabinoid receptors) in the genomes of these or related species. Orthologs were examined for amino acid motifs known to impart functionality to receptors.
In mammals and pigeon, but not amphibians, a significant fraction of the stimulation of [S]GTPγS binding by WIN55212-2 was not blocked by the CB antagonist SR141716A. BLAST searches found that GPR3 was restricted to mammals. GPR12 orthologs existed in all species, and they shared identical amino acid motifs. GPR6 orthologs existed all species, but with significant departures in the identity of some critical amino acids in bird, more so in amphibian.
The portion of WIN55212-2-stimulated [S]GTPγS binding that was antagonized by SR141716A was consistent with stimulation via CB receptors, indicating that antagonist-insensitive activity was via a different G-protein coupled receptor. Pharmacological evidence of this receptor was found in the brains of mammals and pigeon, but not frog or newt. Bioinfomatics results implicate GPR6 as a possible candidate for the additional WIN55212-2-sensitive receptor.
先前的研究在啮齿动物中发现了非CB类G蛋白偶联受体，其可被氨基烷基吲哚大麻素激动剂WIN55212-2激活。本研究旨在获取其他哺乳动物、鸟类和两栖动物大脑中是否存在类似受体的证据。
在大鼠和犬的多个中枢神经系统区域以及鼩鼱、鸽子、青蛙和蝾螈的全脑膜中，评估WIN55212-2和CP55940对[S]GTPγS结合刺激的拮抗作用。采用生物信息学方法在这些物种或相关物种的基因组中搜索GRP3、GPR6和GPR12（与大麻素受体密切相关）的直系同源物。检查直系同源物中已知赋予受体功能的氨基酸基序。
在哺乳动物和鸽子中，而非两栖动物中，WIN55212-2对[S]GTPγS结合的刺激有很大一部分未被CB拮抗剂SR141716A阻断。BLAST搜索发现GPR3仅限于哺乳动物。GPR12直系同源物存在于所有物种中，且它们具有相同的氨基酸基序。GPR6直系同源物存在于所有物种中，但鸟类中一些关键氨基酸的一致性存在显著差异，在两栖动物中差异更大。
SR141716A拮抗的WIN55212-2刺激的[S]GTPγS结合部分与通过CB受体的刺激一致，表明拮抗剂不敏感的活性是通过不同的G蛋白偶联受体介导的。在哺乳动物和鸽子的大脑中发现了该受体的药理学证据，但在青蛙或蝾螈中未发现。生物信息学结果表明GPR6可能是额外的WIN55212-2敏感受体的候选者。
