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g和腺苷酸环化酶（AC）活性来刺激cAMP的产生，从而诱导平滑肌松弛。毒蕈碱乙酰胆碱受体（mAChR）激活Gq和Gi，引起双管齐下的收缩：M3受体介导的细胞内Ca2+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的松弛，但在胃肠道平滑肌中，AR主要通过camp依赖性途径诱导松弛。由于对cAMP的依赖性不同，gi偶联M2受体在胃肠道平滑肌收缩中发挥重要作用，而在气道平滑肌收缩中不起作用。过表达AC6的气道平滑肌显示ar介导的cAMP形成和松弛增强，但不增加基础cAMP水平或对前列腺素EP2受体激活的反应。AC6过表达的选择性作用是由于外源AC6与AR在小泡和脂筏中的区隔以及EP2受体被排除在这些微域之外。由于其他AC异构体的定位与AC6不同，本项目将检测气道和回肠平滑肌中天然AC异构体的表达，然后评估表达脂质筏和非筏定位AC异构体对这两种组织的生化信号传导和收缩张力调节的影响。中心假设是，平滑肌脂筏中受体和AC的定位决定了受体调节收缩张力的信号通路，并且这种定位在平滑肌含组织之间是不同的。目的是了解回肠和气道平滑肌中受体的细胞区隔（主要关注，但不限于BAR和mAChR）和AC的细胞区隔，并确定这种区隔在正常和哮喘气道平滑肌张力调节中的功能重要性。可能通过增强AC表达或功能来选择性调节哮喘或胃肠道疾病的平滑肌功能。

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.