Adenylyl cyclases in airway and GI smooth muscle

描述（由申请人提供）：~-肾上腺素能受体（~ AR）通过激活Gs和腺苷酸环化酶（AC）活性刺激cAMP产生，以诱导平滑肌松弛。毒蕈碱型乙酰胆碱受体（mAChR）激活Gq和Gi两者以引起双管齐下的收缩：M3受体介导的细胞内Ca 2+升高和M2受体介导的AC活性抑制。AR通过cAMP依赖性和非依赖性机制介导气道平滑肌舒张，但在胃肠道平滑肌中，AR主要通过cAMP依赖性途径诱导舒张。由于这种对cAMP的不同依赖性，G1-偶联的M2受体在胃肠平滑肌的收缩中起很大作用，但在气道平滑肌中不起作用。过表达AC 6的气道平滑肌显示增强AR介导的cAMP形成和舒张，但不增加基础cAMP水平或对前列腺素EP 2受体活化的反应。AC 6过表达的这种选择性作用似乎是由于外源性AC 6与微囊和脂筏中的AR的区室化以及EP 2受体从这些微结构域中的排除。由于AC的其他亚型与AC 6定位不同，因此本项目将检查气道和回肠平滑肌中的天然AC亚型表达，然后将评估表达脂筏和非筏定位的AC亚型对这两种组织中的生化信号传导和收缩张力调节的影响。中心假设是受体和AC在平滑肌的脂筏中的定位决定了受体用于调节收缩张力的信号传导途径，并且这种定位在含有平滑肌的组织之间不同。目的是了解回肠和气道平滑肌中受体（主要但不限于BAR和mAChR）和AC的细胞区室化，并确定这种区室化在正常和哮喘气道中调节平滑肌张力的功能重要性。在哮喘或胃肠道疾病中，增强AC表达或功能以选择性地调节平滑肌功能是可能的。

DESCRIPTION (provided by applicant): ¿-adrenergic receptors (¿AR) stimulate cAMP production via activation of Gs and adenylyl cyclase (AC) activity to induce smooth muscle relaxation. Muscarinic acetylcholine receptors (mAChR) activate both Gq and Gi to cause a two-pronged contraction: M3 receptor-mediated elevation of intracellular Ca2+ and M2 receptor-mediated inhibition of AC activity. ¿AR mediate relaxation of airway smooth muscle via both cAMP-dependent and -independent mechanisms but in gastrointestinal smooth muscle ¿AR induce relaxation primarily via cAMP-dependent pathways. As a result of this differing dependence upon cAMP, Gi-coupled M2 receptors play a large role in contraction of gastrointestinal smooth muscle but not in airway smooth muscle. Airway smooth muscle overexpressing AC6 display enhanced ¿AR-mediated cAMP formation and relaxation but not increased basal cAMP levels or response to activation of prostaglandin EP2 receptors. This selective effect of AC6 overexpression appears due to compartmentation of the exogenous AC6 with ¿AR in caveolae and lipid rafts and the exclusion of EP2 receptors from these microdomains. Because other isoforms of AC localize differently than AC6, this project will examine the native AC isoform expression in airway and ileal smooth muscle then will assess the effects of expressing lipid raft and non-raft localized AC isoforms on biochemical signaling and regulation of contractile tone in these two tissues. The central hypothesis is that the localization of receptors and AC's in lipid rafts of smooth muscle determines the signaling pathways used by receptors to regulate contractile tone and that this localization differs between smooth muscle-containing tissues. The goal is to understand the cellular compartmentation of receptors (focusing primarily, but not exclusively, on BAR and mAChR) and AC's in ileal and airway smooth muscle and to determine the functional importance of this compartmentation in regulation of smooth muscle tone in both normal and asthmatic airways. It may be possible to enhance AC expression or function to selectively regulate smooth muscle function in asthma or gastrointestinal disease.