Role of G proteins in agonist-induced Ca2+ sensitization of tracheal smooth muscle
Role of G proteins in agonist-induced Ca2+ sensitization of tracheal smooth muscle
复制标题
DOI：
10.1152/ajplung.1998.275.4.l748
复制
发表时间：
1998-10-01
影响因子：
4.9
通讯作者：
Hirshman, CA
中科院分区：
文献类型：
--
作者：
Croxton, TL;Lande, B;Hirshman, CA
对细胞内钙离子浓度([Ca~(2+)])的敏感性增加是激动剂诱导的气道平滑肌收缩的重要机制，但涉及的信号转导途径尚不清楚。本文研究了乙酰胆碱(ACh)和内皮素(ET)-1对猪气管平滑肌钙离子的增敏作用，方法是测定用α-毒素或β-七叶皂苷通透的条上恒定的[Ca~(2+)]收缩。G蛋白拮抗剂2A(GP Ant-SA)对G(Q)比G(I)具有选择性，可抑制ET-I、ACh和鸟苷5‘-O-(3-硫代三磷酸)(GTP-γS)的收缩反应，但对ACh反应的比例抑制程度小于ET-1。百日咳毒素可减少ACh收缩，但不影响ET-1或GTP-γ肉毒梭菌C3外酶的收缩反应，前者可使Rho家族单体G蛋白失活，后者对ACh、ET-1的收缩反应与抑制RAS-G蛋白的GTP-γ法尼基转移酶抑制类似，后者可降低对ET-1的反应。我们认为，异三聚体G蛋白G(Q)和G(I)都参与了ACh对钙的敏化作用，而ET-1的反应只涉及G(Q)而不涉及G(I)。G(Q)和G(I)途径都可能涉及Rho家族的小G蛋白。RAS介导的通路也参与了ET-1对气道平滑肌细胞内钙离子的增敏作用。
Increased sensitivity to intracellular Ca2+ concentration ([Ca2+]) is an important mechanism for agonist-induced contraction of airway smooth muscle, but the signal transduction pathways involved are uncertain. We studied Ca2+ sensitization with acetylcholine (ACh) and endothelin (ET)-1 in porcine tracheal smooth muscle by measuring contractions at a constant [Ca2+] in strips permeabilized with alpha-toxin or beta-escin. The peptide inhibitor G protein antagonist 2A (GP Ant-SA), which has selectivity for G(q) over G(i), inhibited contractile responses to ET-I,ACh, and guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), but the proportional inhibition of ACh responses was less than that of ET-1. Pretreatment with pertussis toxin reduced ACh contractions but had no effect on those of ET-1 or GTP gamma S. Clostridium botulinum C3 exoenzyme, which inactivates Rho family monomeric G proteins, caused similar reductions in contractile responses to ACh, ET-1, and GTP gamma S. Farnesyltransferase inhibition, which inhibits Ras G proteins, reduced responses to ET-1. We conclude that the heterotrimeric G proteins G(q) and G(i) both contribute to Ca2+ sensitization by ACh, whereas ET-1 responses involve G(q) but not G(i). Both G(q) and G(i) pathways likely involve Rho family small G proteins. A Ras-mediated pathway also contributes to Ca2+ sensitization by ET-1 in airway smooth muscle.