Muscarinic acetylcholine receptor subtypes: physiological roles

摘要 以下总结的结果是通过合作研究获得的： 越来越多的证据表明，气道直径的调节与体重的调节是相互交织的。对不同突变小鼠模型的研究表明，瘦素通过减少由气道平滑肌细胞表达的M3mAChRs而减少副交感神经信号，从而增加了气道直径。此外，副交感神经张力的减少抑制了肥胖小鼠的支气管收缩和肺功能正常化，而与支气管炎无关。这些发现对肥胖相关哮喘的治疗具有潜在的临床意义。 (Arteaga-Solis E，et al.抑制瘦素对副交感神经信号的调节是极端体重相关哮喘的原因。Cell Metab 17，35-48,2013) 慢性阻塞性肺疾病(COPD)的特征是副交感神经胆碱能张力增加。最近的数据表明，ACh也在介导呼吸道炎症中发挥作用。为了确定参与这一活动的mAChR亚型的性质，M1、M2和M3mAChR KO小鼠和WT对照组小鼠被暴露在香烟烟雾中数天。有趣的是，小鼠表型研究的结果表明，M3mAChR在香烟烟雾诱导的中性粒细胞增多和细胞因子释放中具有促炎作用，而M1和M3mAChR在该动物模型中具有抗炎作用。这些发现与开发用于COPD治疗的新型毒鼠强药物高度相关。 (Kistemaker le等人)M受体亚型在香烟烟雾诱导的小鼠炎症中的特异性作用。欧元报告2013年2月8日epub提前打印) 背外侧被盖(LDT)和桥小脚被盖(PPT)核团中的胆碱能神经元通过向中脑多巴胺区域和大脑其他区域的主要投射调节奖赏、觉醒和感觉门控。众所周知，这些胆碱能神经元的活动受毒鼠宁激动剂的调节。为了确定参与这一活动的mAChR亚型的性质，对不同的mAChR KO菌株进行了电生理和钙成像研究。这些实验表明，多个mAChRs以一种出人意料的复杂方式协调从LDT流出的胆碱能。 (Kohlmeier Ka，et al.基因敲除揭示了M2和M4毒碱的重叠功能 被盖背外侧区局部谷氨酸能环路的受体和证据 原子核。神经生理学杂志108,2751-66,2012) 我们最近产生了一个基于M3mAChR的设计者GPCR，它选择性地激活刺激性G蛋白Gs(Guettier等人，PNAS106,19197-2022009年)。这种设计者受体，我们称之为‘Rs’，不能结合内源性mAChR配体ACh，但可以被外源性药物(氯氮平-N-氧化物或简称CNO)选择性地激活。为了探讨Gs信号在纹状体苍白质中棘神经元(MSN)中的行为学作用，用选择性表达Rs结构的转基因小鼠进行了研究。在CNO治疗后，Rs突变小鼠的自发和新奇诱导的运动活动减少，并且没有表现出对苯丙胺的行为敏化。这些发现表明，Rs受体是一种基于M3mAChR的设计者GPCR，是阐明激活纹状体苍白质MSN中Gs信号的行为后果的一种极好的新工具。 (Farrell MS等人)选择性调节纹状体苍白球神经元cAMP生成的S DREADD小鼠。神经精神药理学38,854-62,2013) 背侧纹状体在基于奖赏的决策中发挥作用，但特定纹状体回路在这些过程中的重要性仍不清楚。利用神经元特异性病毒载体，Rs受体(见上一段)在大鼠背内侧纹状体的直接通路(纹状体)神经元中表达。Rs受体是一种基于M3mAChR的GPCR，选择性地与Gs偶联。CNO介导的Rs Designer受体的激活显著改善了在随后的偏好测试中用于最大化奖励获得的任务策略的保持。这些数据表明，直接通路纹状体神经元中的Gs信号在奖赏相关行为中发挥着明确的作用。 (Ferguson SM，et al.直接通路纹状体神经元调节决策策略的保留。J Neurosci 133,11668-76,2013年)

SUMMARY The results summarized below were obtained in collaborative studies: Accumulating evidence suggests that the regulation of airway diameter and body weight are intertwined. Studies with different mutant mouse models demonstrated that leptin increased airway diameter by decreasing parasympathetic signaling through M3 mAChRs expressed by airway smooth muscle cells. Moreover, reduction of parasympathetic tone inhibited bronchoconstriction and normalized lung function in obese mice regardless of bronchial inflammation. These findings are of potential clinical relevance for the treatment of obesity-associated asthma. (Arteaga-Solis E, et al. Inhibition of leptin regulation of parasympathetic signaling as a cause of extreme body weight-associated asthma. Cell Metab 17, 35-48, 2013) Chronic obstructive pulmonary disease (COPD) is characterized by an increase in parasympathetic cholinergic tone. Recent data suggest that ACh also plays a role in mediating airway inflammation. To identify the nature of the mAChR subtypes involved in this activity, M1, M2, and M3 mAChR KO mice and WT control mice were exposed to cigarette smoke for several days. Interestingly, the outcome of mouse phenotyping studies indicated that the M3 mAChR has a pro-inflammatory role in cigarette smoke-induced neutrophilia and cytokine release, whereas the M1 and M3 mAChRs exert anti-inflammatory effects in this animal model. These findings are highly relevant for the development of novel muscarinic drugs useful for the treatment of COPD. (Kistemaker LE, et al. Muscarinic receptor subtype-specific effects on cigarette smoke-induced inflammation in mice. Eur Respir J Feb 8, 2013 Epub ahead of print) Cholinergic neurons in the laterodorsal tegmental (LDT) and peduncolopontine tegmental (PPT) nuclei regulate reward, arousal, and sensory gating via major projections to midbrain dopamine regions and other areas of the brain. It is well known that the activity of these cholinergic neurons is modulated by muscarinic agonists. To identify the nature of the mAChR subtypes involved in this activty, various mAChR KO strains were subjected to electrophysiological and calcium imaging studies. These experiments demonstrated that multiple mAChRs coordinate cholinergic outflow from the LDT in an unexpectedly complex manner. (Kohlmeier KA, et al. Knockouts reveal overlapping functions of M2 and M4 muscarinic receptors and evidence for a local glutamatergic circuit within the laterodorsal tegmental nucleus. J Neurophysiol 108, 2751-66, 2012) We recently generated an M3 mAChR-based designer GPCR that selectively activates the stimulatory G protein, Gs (Guettier et al., PNAS 106, 19197-202, 2009). This designer receptor, which we refer to as 'Rs', is unable to bind ACh, the endogenous mAChR ligand, but can be selectively activated by an exogenously administered drug that is otherwise pharmacologically inert (clozapine-N-oxide or short CNO). To explore the behavioral roles of Gs signaling in striatopallidal medium spiny neurons (MSNs), studies were carried out with transgenic mice selectively expressing the Rs construct in these neurons. Following CNO treatment, the Rs mutant mice showed reduced spontaneous and novelty-induced locomotor activity and failed to display behavioral sensitization to amphetamine. These findings demonstrate that the Rs receptor, an M3 mAChR-based designer GPCR, represents an excellent novel tool for elucidating the behavioral consequences of activating Gs signaling in striatopallidal MSNs. (Farrell MS, et al. A Gαs DREADD mouse for selective modulation of cAMP production in striatopallidal neurons. Neuropsychopharmacology 38, 854-62, 2013) The dorsal striatum plays a role in reward-based decision making, but the importance of specific striatal circuits in these processes remains unclear. By using neuron-specific viral vectors, the Rs receptor (see previous paragraph), an M3 mAChR-based designer GPCR that is selectively coupled to Gs, was expressed in direct-pathway (striatonigral) neurons of the dorsomedial striatum of the rat. CNO-mediated activation of the Rs designer receptor significantly improved the retention of task strategies used to maximize reward obtainment during subsequent preference testing. These data demonstrate that Gs signaling in direct-pathway striatal neurons plays a well-defined role in reward-related behavior. (Ferguson SM, et al. Direct-pathway striatal neurons regulate the retention of decision-making strategies. J Neurosci 133, 11668-76, 2013)