Role of pertussis toxin-sensitive G-proteins in intracellular Ca2+ release and apoptosis induced by inhibiting cystic fibrosis transmembrane conductance regulator (CFTR) Cl? channels in HepG2 human hepatoblastoma cells

2001 ◽  
Vol 81 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Jung-Ae Kim ◽  
Young Shin Kang ◽  
Sun Hee Lee ◽  
Eun-Hee Lee ◽  
Yong Soo Lee
Keyword(s):  
Cystic Fibrosis ◽  
G Proteins ◽  
Pertussis Toxin ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Cl Channels ◽  
Cystic Fibrosis Transmembrane

scholarly journals Effect of ATP-sensitive K+ channel regulators on cystic fibrosis transmembrane conductance regulator chloride currents.

1992 ◽  
Vol 100 (4) ◽  
pp. 573-591 ◽  
Author(s):  
D N Sheppard ◽  
M J Welsh
Keyword(s):  
Cystic Fibrosis ◽  
Voltage Dependence ◽  
K Channel ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
K Channels ◽  
Intracellular Atp ◽  
Cl Channel ◽  
Cl Channels ◽  
Cystic Fibrosis Transmembrane

The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl- channel that is regulated by cAMP-dependent phosphorylation and by intracellular ATP. Intracellular ATP also regulates a class of K+ channels that have a distinct pharmacology: they are inhibited by sulfonylureas and activated by a novel class of drugs called K+ channel openers. In search of modulators of CFTR Cl- channels, we examined the effect of sulfonylureas and K+ channel openers on CFTR Cl- currents in cells expressing recombinant CFTR. The sulfonylureas, tolbutamide and glibenclamide, inhibited whole-cell CFTR Cl- currents at half-maximal concentrations of approximately 150 and 20 microM, respectively. Inhibition by both agents showed little voltage dependence and developed slowly; > 90% inhibition occurred 3 min after adding 1 mM tolbutamide or 100 microM glibenclamide. The effect of tolbutamide was reversible, while that of glibenclamide was not. In contrast to their activating effect on K+ channels, the K+ channel openers, diazoxide, BRL 38227, and minoxidil sulfate inhibited CFTR Cl- currents. Half-maximal inhibition was observed at approximately 250 microM diazoxide, 50 microM BRL 38227, and 40 microM minoxidil sulfate. The rank order of potency for inhibition of CFTR Cl- currents was: glibenclamide < BRL 38227 approximately equal to minoxidil sulfate > tolbutamide > diazoxide. Site-directed mutations of CFTR in the first membrane-spanning domain and second nucleotide-binding domain did not affect glibenclamide inhibition of CFTR Cl- currents. However, when part of the R domain was deleted, glibenclamide inhibition showed significant voltage dependence. These agents, especially glibenclamide, which was the most potent, may be of value in identifying CFTR Cl- channels. They or related analogues might also prove to be of value in treating diseases such as diarrhea, which may involve increased activity of the CFTR Cl- channel.

CFTR mediates electrogenic chloride secretion in mouse inner medullary collecting duct (mIMCD-K2) cells

1995 ◽  
Vol 269 (3) ◽  
pp. C683-C689 ◽  
Author(s):  
D. Vandorpe ◽  
N. Kizer ◽  
F. Ciampollilo ◽  
B. Moyer ◽  
K. Karlson ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Patch Clamp ◽  
Collecting Duct ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Inner Medullary Collecting Duct ◽  
Cl Channel ◽  
Cl Channels ◽  
Medullary Collecting Duct ◽  
Cystic Fibrosis Transmembrane

Previously we demonstrated that the inner medullary collecting duct cell line mIMCD-K2 secretes Cl- by an electrogenic mechanism [N. L. Kizer, B. Lewis, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F347-F355, 1995; N. L. Kizer, D. Vandorpe, B. Lewis, B. Bunting, J. Russell, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F854-F861, 1995]. The goal of the present study was to characterize the Cl- channel responsible for adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated Cl- secretion. To this end, using the patch-clamp technique, we measured Cl- currents. In whole cell patch-clamp experiments, 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP) activated Cl- currents that were time and voltage independent, inhibited by diphenylamine 2-carboxylate (DPC), and had a linear current-voltage (I-V) relation. In cell-attached patches of the apical membrane, we identified 7-pS Cl- channels that were stimulated by CPT-cAMP. In inside-out patches with Cl- in the pipette and bath solutions, Cl- currents had a linear I-V relation. The halide permeability sequence was PCl = PBr > PI. The Cl- channel inhibitors DPC, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, and glibenclamide blocked the 7-pS Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid was ineffective. By reverse transcriptase polymerase chain reaction, we isolated a partial cDNA clone encoding the cystic fibrosis transmembrane conductance regulator in mIMCD-K2 cells. We conclude that cAMP stimulates electrogenic Cl- secretion in inner medullary collecting duct cells by activating cystic fibrosis transmembrane conductance regulator Cl- channels.

scholarly journals ΔF508 CFTR Pool in the Endoplasmic Reticulum Is Increased by Calnexin Overexpression

2004 ◽  
Vol 15 (2) ◽  
pp. 563-574 ◽  
Author(s):  
Tsukasa Okiyoneda ◽  
Kazutsune Harada ◽  
Motohiro Takeya ◽  
Kaori Yamahira ◽  
Ikuo Wada ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Endoplasmic Reticulum ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Δf508 Cftr ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway ◽  
Cystic Fibrosis Transmembrane ◽  
Erad Pathway

The most common cystic fibrosis transmembrane conductance regulator (CFTR) mutant in cystic fibrosis patients, ΔF508 CFTR, is retained in the endoplasmic reticulum (ER) and is consequently degraded by the ubiquitin-proteasome pathway known as ER-associated degradation (ERAD). Because the prolonged interaction of ΔF508 CFTR with calnexin, an ER chaperone, results in the ERAD of ΔF508 CFTR, calnexin seems to lead it to the ERAD pathway. However, the role of calnexin in the ERAD is controversial. In this study, we found that calnexin overexpression partially attenuated the ERAD of ΔF508 CFTR. We observed the formation of concentric membranous bodies in the ER upon calnexin overexpression and that the ΔF508 CFTR but not the wild-type CFTR was retained in the concentric membranous bodies. Furthermore, we observed that calnexin overexpression moderately inhibited the formation of aggresomes accumulating the ubiquitinated ΔF508 CFTR. These findings suggest that the overexpression of calnexin may be able to create a pool of ΔF508 CFTR in the ER.

scholarly journals The CFTR and ENaC debate: how important is ENaC in CF lung disease?

2012 ◽  
Vol 302 (11) ◽  
pp. L1141-L1146 ◽  
Author(s):  
James F. Collawn ◽  
Ahmed Lazrak ◽  
Zsuzsa Bebok ◽  
Sadis Matalon
Keyword(s):  
Cystic Fibrosis ◽  
Lung Disease ◽  
Bacterial Infections ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Ongoing Debate ◽  
The Subject ◽  
Cystic Fibrosis Transmembrane ◽  
Epithelial Sodium Channel Enac

Cystic fibrosis (CF) is caused by the loss of the cystic fibrosis transmembrane conductance regulator (CFTR) function and results in a respiratory phenotype that is characterized by dehydrated mucus and bacterial infections that affect CF patients throughout their lives. Much of the morbidity and mortality in CF results from a failure to clear bacteria from the lungs. What causes the defect in the bacterial clearance in the CF lung has been the subject of an ongoing debate. Here we discuss the arguments for and against the role of the epithelial sodium channel, ENaC, in the development of CF lung disease.

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