Department of Psychological and Brain Sciences, Gill Center for Biomolecular Science, Indiana University, Bloomington, IN 47405, USA.
Br J Pharmacol. 2012 Apr;165(8):2652-9. doi: 10.1111/j.1476-5381.2011.01743.x.
The cannabinoid CB(1) receptor is the chief mediator of the CNS effects of cannabinoids. In cell culture model systems, CB(1) receptors both desensitize and internalize on activation. Previous work suggests that the extreme carboxy-terminus of this receptor regulates internalization via phosphorylation of residues clustered within this region. Mutational analysis of the carboxy-terminus of CB(1) receptors has demonstrated that the last six serine/threonine residues are necessary for agonist-induced internalization. However, the structural determinants of CB(1) receptor internalization are also dependent on the local cellular environment. The importance of cell context on CB(1) receptor function calls for an investigation of the functional roles of these residues in neurones.
To determine the structural requirements of CB(1) internalization in neurones, we evaluated the signalling properties of carboxy-terminal mutated CB(1) receptors expressed in cultured autaptic hippocampal neurones, using electrophysiological methods.
CB(1) receptors transfected into CB(1) knockout neurones signalled and desensitized as did wild-type neurones, allowing us to test specific CB(1) receptor mutations. Deletion of the last 13 residues yielded a CB(1) receptor that inhibited excitatory postsynaptic currents but did not desensitize. Furthermore, mutation of the final six serine and threonine residues to alanines resulted in a non-desensitizing receptor. In contrast, CB(1) receptors lacking residues 419-460, leaving the last 14 residues intact, did desensitize.
The distal thirteen residues of CB(1) receptors are crucial for their desensitization in cultured neurones. Furthermore, this desensitization is likely to follow phosphorylation of serines and threonines within this region.
This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.
大麻素 CB（1）受体是大麻素对中枢神经系统作用的主要介导者。在细胞培养模型系统中，CB（1）受体在激活时会脱敏和内化。先前的工作表明，该受体的羧基末端极区通过该区域内聚集的残基的磷酸化来调节内化。CB（1）受体羧基末端的突变分析表明，最后六个丝氨酸/苏氨酸残基是激动剂诱导内化所必需的。然而，CB（1）受体内化的结构决定因素也依赖于局部细胞环境。细胞环境对 CB（1）受体功能的重要性要求对这些残基在神经元中的功能作用进行研究。
为了确定神经元中 CB（1）内化的结构要求，我们使用电生理学方法评估了在培养的自突触海马神经元中表达的羧基末端突变 CB（1）受体的信号转导特性。
转染到 CB（1）受体敲除神经元中的 CB（1）受体与野生型神经元一样发出信号并脱敏，从而使我们能够测试特定的 CB（1）受体突变。缺失最后 13 个残基产生了一种抑制兴奋性突触后电流但不脱敏的 CB（1）受体。此外，将最后六个丝氨酸和苏氨酸残基突变为丙氨酸导致非脱敏受体。相比之下，缺失 419-460 个残基的 CB（1）受体仍能脱敏。
CB（1）受体的远端 13 个残基对于它们在培养神经元中的脱敏至关重要。此外，这种脱敏可能是通过该区域内丝氨酸和苏氨酸的磷酸化来实现的。
本文是关于大麻素在生物学和医学中的主题部分的一部分。要查看该部分中的其他文章，请访问 http://dx.doi.org/10.1111/bph.2012.165.issue-8。要查看大麻素在生物学和医学中的第一部分，请访问 http://dx.doi.org/10.1111/bph.2011.163.issue-7。
