Guanine nucleotides induce Ca2+-independent insulin secretion from permeabilized RINm5F cells.
Guanine nucleotides induce Ca2+-independent insulin secretion from permeabilized RINm5F cells.
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鸟嘌呤核苷酸诱导透化 RINm5F 细胞分泌不依赖 Ca2+ 的胰岛素。
DOI：
10.1016/s0021-9258(18)61152-4
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
C. Wollheim
中科院分区：
文献类型：
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作者：
L. Vallar;T. Biden;C. Wollheim
在电通透性RINm5F细胞中，研究了鸟嘌呤核苷酸在胰岛素分泌中的作用。钙离子刺激胰岛素释放(EC50约2微米钙离子)。GTP稳定类似物，GTP伽玛S，在极低的Ca~(2+)浓度(小于10(-11)M)时刺激胰岛素分泌，轻微增强对中等Ca~(2+)水平的反应，但在最大Ca~(2+)浓度时作用不明显。国内生产总值类似物，国内生产总值βS，既抑制GTPγS刺激的分泌，也抑制钙刺激的分泌。GTP-γS的这一作用不是由cAMP介导的，后者只促进钙离子诱导的分泌。相比之下，蛋白激酶C的激活剂12-O-十四烷基佛波酯-13-乙酸酯在非刺激性钙水平上促进胰岛素释放，并增强钙反应。GTP类似物刺激磷脂酰肌醇4，5-二磷酸(PtdInsP2)的水解，通过产生肌醇磷酸来评估。然而，这不能完全解释鸟嘌呤核苷酸诱导的PtdInsP2的分泌，因为：GTP-γS刺激的PtdInsP2的分解完全依赖于Ca~(2+)，当Ca~(2+)浓度低于10(-11)M时，蛋白激酶C的激活剂是弱的或无效的分泌剂；GTP类似物GPP(NH)p激活PtdInsP2的活性远低于GTP-γ-S，但完全模拟了对Ca~(2+)非依赖性分泌的影响。S诱导的PtdInsP2水解和胰岛素释放对百日咳毒素和霍乱毒素均不敏感。这些发现指出，在胰岛素分泌的激活中有一个鸟嘌呤核苷酸调节的位置，不同于已知的跨膜信号系统。
The role of guanine nucleotides in insulin secretion was investigated in electrically permeabilized RINm5F cells. Ca2+ stimulated insulin release (EC50 approximately 2 microM Ca2+). The GTP stable analog, GTP gamma S, elicited insulin secretion at vanishingly low Ca2+ concentrations (less than 10(-11) M), slightly potentiated the response to intermediate Ca2+ levels, but exerted less than additive effects at maximal Ca2+ concentrations. The GDP analog, GDP beta S, inhibited both GTP gamma S- and Ca2+-stimulated secretion. The action of GTP gamma S was not mediated by cAMP, as the latter only enhanced Ca2+-induced secretion. In contrast, 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, promoted insulin release at nonstimulatory Ca2+ levels as well as potentiating the Ca2+ response. GTP analogs stimulated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdInsP2), as assessed by inositol phosphate generation. However, this could not fully explain guanine nucleotide-induced secretion because: GTP gamma S-stimulated PtdInsP2 breakdown was totally dependent on Ca2+ and abolished at Ca2+ below 10(-11) M; at these Ca2+ levels, activators of protein kinase C were weak or ineffective secretagogues; the GTP analog Gpp(NH)p was much less effective than GTP gamma S in activating PtdInsP2 hydrolysis, while fully mimicking the effect on Ca2+-independent secretion. Both GTP gamma S-induced PtdInsP2 hydrolysis and insulin release were insensitive to pertussis toxin and cholera toxin. The findings point to a guanine nucleotide-regulated site in the activation of insulin secretion different from the known transmembrane signalling systems.