Barriere Herve, Bagdany Miklos, Bossard Florian, Okiyoneda Tsukasa, Wojewodka Gabriella, Gruenert Dieter, Radzioch Danuta, Lukacs Gergely L
Department of Physiology, McGill University, Montreal, Quebec, H3G 1Y6, Canada.
Mol Biol Cell. 2009 Jul;20(13):3125-41. doi: 10.1091/mbc.e09-01-0061. Epub 2009 May 6.
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.
通过电生空泡质子 - ATP酶进行的细胞器酸化与阴离子摄取和阳离子外流相偶联，以维持电中性。由突变的囊性纤维化跨膜传导调节因子（CFTR）的反离子传导受损引起的细胞器pH调节缺陷，在上皮细胞和巨噬细胞中仍存在高度争议。将pH敏感探针限制在含有CFTR的囊泡中，在各种细胞中测量反离子和质子通透性以及内体的腔pH，包括基因匹配的CF和非CF人类呼吸道上皮细胞，以及cftr(+/+)和cftr(-/-)小鼠肺泡巨噬细胞。分别用异硫氰酸荧光素（FITC）偶联的转铁蛋白、葡聚糖和铜绿假单胞菌探测内体、溶酶体和吞噬体pH调节的决定因素——被动质子和相对反离子通透性。尽管CFTR功能可在循环内体和未成熟吞噬体中得到证明，但通道激活或抑制均未影响这些细胞器中的任何一个的pH。CFTR异源过表达也未能改变内吞细胞器的pH。我们提出，相对较大的与CFTR无关的反离子和较小的被动质子通透性可确保质子 - ATP酶产生的膜电位有效分流。这些结果总体上对细胞器酸化的调节具有启示意义，并表明内溶酶体细胞器pH稳态的扰动与CF肺部疾病的病因无关。
