Proton leak and CFTR in regulation of Golgi pH in respiratory epithelial cells

Grischa Chandy, Michael Grabe, Hsiao-Ping H. Moore, Terry E. Machen
2001 American Journal of Physiology - Cell Physiology  
Chandy, Grischa, Michael Grabe, Hsiao-Ping H. Moore, and Terry E. Machen. Proton leak and CFTR in regulation of Golgi pH in respiratory epithelial cells. Am J Physiol Cell Physiol 281: C908-C921, 2001.-Work addressing whether cystic fibrosis transmembrane conductance regulator (CFTR) plays a role in regulating organelle pH has remained inconclusive. We engineered a pH-sensitive excitation ratiometric green fluorescent protein (pHERP) and targeted it to the Golgi with sialyltransferase (ST). As
more » ... ansferase (ST). As determined by ratiometric imaging of cells expressing ST-pHERP, Golgi pH (pHG) of HeLa cells was 6.4, while pH G of mutant (⌬F508) and wildtype CFTR-expressing (WT-CFTR) respiratory epithelia were 6.7-7.0. Comparison of genetically matched ⌬F508 and WT-CFTR cells showed that the absence of CFTR statistically increased Golgi acidity by 0.2 pH units, though this small difference was unlikely to be physiologically important. Golgi pH was maintained by a H ϩ vacuolar (V)-ATPase countered by a H ϩ leak, which was unaffected by CFTR. To estimate Golgi proton permeability (P H ϩ), we modeled transient changes in pH G induced by inhibiting the V-ATPase and by acidifying the cytosol. This analysis required knowing Golgi buffer capacity, which was pH dependent. Our in vivo estimate is that Golgi P H ϩ ϭ 7.5 ϫ 10 Ϫ4 cm/s when pHG ϭ 6.5, and surprisingly, P H ϩ decreased as pHG decreased.
doi:10.1152/ajpcell.2001.281.3.c908 pmid:11502568 fatcat:n7bfyo35rjcdtgbu4ebhr5uazi