Revisiting the Role of Cystic Fibrosis Transmembrane Conductance Regulator and Counterion Permeability in the pH Regulation of Endocytic Organelles
Revisiting the Role of Cystic Fibrosis Transmembrane Conductance Regulator and Counterion Permeability in the pH Regulation of Endocytic Organelles
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DOI：
10.1091/mbc.e09-01-0061
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发表时间：
2009-07-01
影响因子：
3.3
通讯作者：
Lukacs, Gergely L.
中科院分区：
文献类型：
--
作者：
Barriere, Herve;Bagdany, Miklos;Lukacs, Gergely L.
产生电生液泡质子-ATPase的细胞器酸化与阴离子摄取和阳离子流出相耦合，以保持电子中性性。由于突变型囊性纤维化跨膜电导调节器(CFTR)的反离子电导受损而引起的细胞器pH调节缺陷，在上皮和巨噬细胞中仍存在很大争议。将pH敏感的探针限制在含有CFTR的囊泡上，在不同的细胞中测量了内体的反离子和质子通透性以及管腔pH，包括遗传匹配的人呼吸道上皮细胞和CFTR(+/+)和CFTR(-/-)小鼠肺泡巨噬细胞。用FITC标记的转铁蛋白、葡聚糖和铜绿假单胞菌分别检测了内质粒、溶酶体和吞噬体pH调节的决定因素--被动质子通透性和相对反离子通透性。尽管CFTR在内小体和未成熟的吞噬小体的循环中发挥作用，但通道的激活和抑制都不影响这些细胞器的pH。CFTR异源过表达也不能改变胞内细胞器的pH值。我们认为，相对较大的非CFTR反离子和较小的被动质子渗透率确保了质子-ATPase产生的膜电位的有效分流。这些结果对细胞器酸化的调节具有普遍意义，并表明内溶酶体细胞器pH动态平衡的紊乱与CF肺部疾病的病因无关。
Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr(+/+) and cftr(-/-) mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase-generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease.