Gray D W, Whitham E M, Challiss R A, Nahorski S R
Department of Cell Physiology and Pharmacology, University of Leicester, England.
J Neurochem. 1995 Mar;64(3):1143-51. doi: 10.1046/j.1471-4159.1995.64031143.x.
A detailed analysis of the generation and subsequent metabolism of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] following muscarinic cholinoceptor stimulation in primary cultures of rat cerebellar granule cells has been undertaken. Following incubation of cerebellar granule cell cultures with [3H]inositol for 48 h, labelling of the inositol phospholipid pool approached equilibrium. Significant basal labelling of inositol pentakisphosphate (InsP5) and inositol hexakisphosphate (InsP6), as well as inositol mono- to tetrakisphosphate, fractions was observed. Addition of carbachol (1 mM) caused an immediate increase in level of Ins(1,4,5)P3 (peak increase two-fold over basal by 60 s), which was well-maintained over the initial 300 s following agonist addition. In contrast, only a modest, more slowly developing, increase in inositol tetrakisphosphate accumulation was observed, whereas labelling of InsP5 and InsP6 was entirely unaffected by carbachol stimulation. Analysis of the products of Ins(1,4,5)P3 and inositol 1,3,4,5-tetrakisphosphate metabolism in broken cell preparations strongly suggested that Ins(1,4,5)P3 metabolism occurs predominantly via the inositol polyphosphate 5-phosphatase route, with metabolism via the Ins(1,4,5)P3 3-kinase being a relatively minor pathway. In view of the pattern of inositol (poly)phosphate metabolites observed on stimulation of the muscarinic receptor, it seems likely that, over the time course studied, the inositol polyphosphates are derived principally from phosphoinositide-specific phospholipase C hydrolysis of phosphatidylinositol 4,5-bisphosphate, although some hydrolysis of phosphatidyl-inositol 4-phosphate cannot be excluded.
已对大鼠小脑颗粒细胞原代培养物中毒蕈碱型胆碱能受体刺激后肌醇1,4,5 -三磷酸[Ins(1,4,5)P3]的生成及后续代谢进行了详细分析。在用[3H]肌醇孵育小脑颗粒细胞培养物48小时后，肌醇磷脂池的标记接近平衡。观察到肌醇五磷酸（InsP5）和肌醇六磷酸（InsP6）以及肌醇一磷酸至四磷酸部分有显著的基础标记。加入卡巴胆碱（1 mM）导致Ins(1,4,5)P3水平立即升高（在60秒时峰值比基础值增加两倍），在加入激动剂后的最初300秒内保持良好。相比之下，仅观察到肌醇四磷酸积累有适度的、发展较慢的增加，而InsP5和InsP6的标记完全不受卡巴胆碱刺激的影响。对破碎细胞制剂中Ins(1,4,5)P3和肌醇1,3,4,5 -四磷酸代谢产物的分析强烈表明，Ins(1,4,5)P3代谢主要通过肌醇多磷酸5 -磷酸酶途径进行，通过Ins(1,4,5)P3 3 -激酶的代谢是一条相对次要的途径。鉴于在毒蕈碱受体刺激下观察到的肌醇（多）磷酸代谢物模式，在研究的时间进程中，肌醇多磷酸似乎主要来源于磷脂酰肌醇4,5 -二磷酸的磷酸肌醇特异性磷脂酶C水解，尽管不能排除磷脂酰肌醇4 -磷酸的一些水解。
