From the Cystic Fibrosis/Pulmonary Research and Treatment Center.
J Biol Chem. 2014 Mar 14;289(11):7671-81. doi: 10.1074/jbc.M113.545137. Epub 2014 Jan 21.
Chronic obstructive pulmonary disease affects 64 million people and is currently the fourth leading cause of death worldwide. Chronic obstructive pulmonary disease includes both emphysema and chronic bronchitis, and in the case of chronic bronchitis represents an inflammatory response of the airways that is associated with mucus hypersecretion and obstruction of small airways. Recently, it has emerged that exposure to cigarette smoke (CS) leads to an inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, causing airway surface liquid dehydration, which may play a role in the development of chronic bronchitis. CS rapidly clears CFTR from the plasma membrane and causes it to be deposited into aggresome-like compartments. However, little is known about the mechanism(s) responsible for the internalization of CFTR following CS exposure. Our studies revealed that CS triggered a rise in cytoplasmic Ca(2+) that may have emanated from lysosomes. Furthermore, chelation of cytoplasmic Ca(2+), but not inhibition of protein kinases/phosphatases, prevented CS-induced CFTR internalization. The macrolide antibiotic bafilomycin A1 inhibited CS-induced Ca(2+) release and prevented CFTR clearance from the plasma membrane, further linking cytoplasmic Ca(2+) and CFTR internalization. We hypothesize that CS-induced Ca(2+) release prevents normal sorting/degradation of CFTR and causes internalized CFTR to reroute to aggresomes. Our data provide mechanistic insight into the potentially deleterious effects of CS on airway epithelia and outline a hitherto unrecognized signaling event triggered by CS that may affect the long term transition of the lung into a hyper-inflammatory/dehydrated environment.
慢性阻塞性肺疾病影响全球 6400 万人,是目前全球第四大死亡原因。慢性阻塞性肺疾病包括肺气肿和慢性支气管炎,在慢性支气管炎的情况下,它代表了气道的炎症反应,与黏液分泌过多和小气道阻塞有关。最近,已经出现暴露于香烟烟雾(CS)会导致囊性纤维化跨膜电导调节因子(CFTR)Cl(-)通道的抑制,引起气道表面液体脱水,这可能在慢性支气管炎的发展中起作用。CS 会迅速从质膜中清除 CFTR,并使其沉积到聚集体样隔室中。然而,对于 CS 暴露后 CFTR 内化的机制知之甚少。我们的研究表明,CS 引发了细胞质 Ca(2+)的上升,这可能源自溶酶体。此外,螯合细胞质 Ca(2+),而不是抑制蛋白激酶/磷酸酶,可防止 CS 诱导的 CFTR 内化。大环内酯类抗生素巴弗洛霉素 A1 抑制 CS 诱导的 Ca(2+)释放并阻止 CFTR 从质膜清除,进一步将细胞质 Ca(2+)与 CFTR 内化联系起来。我们假设 CS 诱导的 Ca(2+)释放阻止了 CFTR 的正常分拣/降解,并导致内化的 CFTR重新路由到聚集体。我们的数据为 CS 对气道上皮的潜在有害影响提供了机制上的见解,并概述了 CS 触发的迄今为止尚未被认识到的信号事件,该事件可能影响肺向高度炎症/脱水环境的长期转变。