Specific and nonspecific effects of nucleotides on hormone‐induced phosphoinositide turnover in permeabilized human pituitary tumour cells (Flow 9000)

[摘要]

Previous studies have shown that agonist-induced inositol phosphate formation in the human embryonic pituitary cell line Flow 9000 is regulated by guanine nucleotides, and it is likely that a guanine nucleotide-binding protein is involved in coupling receptors to phosphoinositidase C (PIC) [(1986) Biochem.Soc. Trans. 14, 1135–1136]. We have now tested the specificity of various nucleotides in regulating PIC activity in the absence or presence of the hormone cholecystokinin (CCK-8) in saponin-permeabilized [³H]inositol-labelled Flow 9000 cells. We found that all nucleotides tested (i.e. CTP, UTP, ITP, TTP, GTP, GppNHp, GTP[S], ATP, AppNHp and ATP[S]) stimulated total [³H]inositol phosphate (³H]IP) formation in a dose-dependent manner with similar potency and efficacy. However, only guanine nucleotides significantly enhanced CCK-8 stimulation of [³H]IP production. These results indicate a physiological role for guanine nucleotides in regulating hormone-induced phosphoinositide turnover. In addition, the effects of nucleotides on calcium-dependent PIC activity are discussed.

[学科分类] 生物化学/生物物理

[关键词] G-protein;Nucleotide;Phosphoinositide;Ca2+;Cholecystokinin;(Flow 9000 cell);CCK-8;cholecystokinin octapeptide (sulphated);ATP[S];adenosine-5′-O-(3-thiotriphosphate);AppNHp;adenylylimidodiphosphate;GTP[S];guanosine-5′-O-(3-thiotriphosphate);GppNHp;guanylylimidodiphosphate;GDP-β-S;guanosine-5′-O-(2-thiodiphosphate)