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.
Previously, we have reported that inhibition of cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels by glibenclamide induced intracellular Ca2+ release from IP(3)-sensitive stores and apoptosis in HepG2 human hepatoblastoma cells (Kim JA, Kang YS, Lee SH, Lee EH, Yoo BH, Lee YS. 1999. Biochem Biophys Res Commun 261:682-688). In this study we investigated the upstream signals involved in the mechanism of these actions of glibenclamide. Treatment with glibenclamide initiated production of inositol 1,4,5-trisphosphate (IP(3)) in a dose- and time-dependent manner. The glibenclamide-induced formation of IP(3) was significantly inhibited by CFTR activators (levamisole and bromotetramisole). The intracellular Ca2+ release and apoptosis induced by glibenclamide were significantly suppressed by treatment with phospholipase C (PLC) inhibitors (U-73122 and manoalide) or by pretreatment with pertussis toxin (PTx). In addition, PTx-catalyzed ADP-ribosylation of GTP-binding proteins (G-proteins) was markedly enhanced by treatment with glibenclamide in a time-dependent manner. Taken together, these results suggest that PTx-sensitive G-proteins coupled to PLCbeta may mediate the intracellular Ca2+ release and apoptosis induced by inhibiting CFTR Cl- channels in HepG2 cells. These results further suggest that the PTx-sensitive G-proteins may be a valuable target for the therapeutic intervention of human hepatomas.
Kim
J A
JA
College of Pharmacy, Yeungnam University, Korea.
Kang
Y S
YS
Lee
S H
SH
Lee
E H
EH
Lee
Y S
YS
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D002384:Catalysis; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D018197:Hepatoblastoma / Q000378:metabolism* / Q000473:pathology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D037342:Pertussis Toxin; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000246:Adenosine Diphosphate Ribose; D015544:Inositol 1,4,5-Trisphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D005905:Glyburide; D002118:Calcium