GTP-mediated Ca2+ release in rough endoplasmic reticulum. Correlation with a GTP-sensitive increase in membrane permeability.
GTP-mediated Ca2+ release in rough endoplasmic reticulum. Correlation with a GTP-sensitive increase in membrane permeability.
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GTP 介导的粗面内质网 Ca2+ 释放。
DOI：
10.1042/bj2480741
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Williamson,JR
中科院分区：
文献类型：
--
作者：
Nicchitta,CV;Joseph,SK;Williamson,JR
据报道，鸟嘌呤核苷酸可刺激网状 Ca2+ 释放。通过使用微粒体甘露糖 6-磷酸磷酸酶的结构相关潜伏期作为微粒体渗透性的指标 [Arion, Ballas, Lange & Wallin (1976) J. Biol.化学。 251, 4901-4907]，比较了 GTP 对肝微粒体中 Ca2+ 释放和膜通透性的影响。在剥离的粗微粒体制剂中，GTP 引起 6-磷酸甘露糖渗透性的剂量依赖性增加。分别在 3 microM-和 10 microM-GTP 下观察到半最大和最大效应。膜通透性变化的时间过程与GTP依赖性Ca2+释放的时间过程一致。微粒体通透性的增加相对于 GTP 表现出积极的手术性（希尔系数 = 1.8）。与 GTP 依赖性 Ca2+ 释放过程类似，鸟苷 5'-γ-硫代]三磷酸和鸟苷 5'-β γ-亚氨基]-三磷酸抑制 GTP 改变微粒体通透性的能力，但单独添加时没有效果。在 50 microM-GTP 存在的情况下，使用 10 microM-鸟苷 5'-[γ-硫代]三磷酸可完全抑制 GTP 依赖性微粒体通透性增加，而使用 10 microM-鸟苷 5'-β-亚氨基]三磷酸则观察到 25% 的抑制。与之前在粗微粒体制剂中观察到的结果相反，剥离的粗微粒体制剂中GTP依赖性Ca2+释放不需要添加聚乙二醇，尽管后者确实刺激了Ca2+释放速率。 GTP 改变微粒体通透性的能力被硫醇试剂对羟基汞苯甲酸酯的预先处理所阻断；暴露于 50 µM 10 分钟后观察到完全抑制。随后用二硫苏糖醇治疗可逆转抑制作用。两个 GTP 敏感过程之间的显着相似性表明它们可能通过相同的机制发挥作用。
Guanine nucleotides have been reported to stimulate reticular Ca2+ release. By using the structure-linked latency of microsomal mannose-6-phosphate phosphatase as an index of microsomal permeability [Arion, Ballas, Lange & Wallin (1976) J. Biol. Chem. 251, 4901-4907], the effects of GTP on Ca2+ release and membrane permeability were compared in liver microsomes. In a stripped rough-microsome preparation, GTP caused a dose-dependent increase in mannose 6-phosphate permeability. Half-maximal and maximal effects were observed at 3 microM- and 10 microM-GTP respectively. The time course of the change in membrane permeability coincided with the time course of GTP-dependent Ca2+ release. This increase in microsomal permeability displayed positive to-operativity with respect to GTP (Hill coefficient = 1.8). By analogy to the GTP-dependent Ca2+ release process, guanosine 5′-[gamma-thio]triphosphate and guanosine 5′-[beta gamma-imido]-triphosphate inhibited the ability of GTP to alter microsomal permeability, but were without effect when added alone. In the presence of 50 microM-GTP, complete inhibition of the GTP-dependent increase in microsomal permeability was achieved with 10 microM-guanosine 5′-[gamma-thio]triphosphate, whereas a 25% inhibition was observed with 10 microM-guanosine 5′-[beta gamma-imido]triphosphate. In contrast with previous observations in crude microsomal preparations, GTP-dependent Ca2+ release in the stripped rough-microsome preparation did not require the addition of poly(ethylene glycol), although the latter did stimulate the rate of Ca2+ release. The ability of GTP to alter microsomal permeability was blocked by prior treatment with the thiol reagent p-hydroxymercuribenzoate; complete inhibition was observed after a 10 min exposure to 50 microM. Inhibition was reversed by subsequent treatment with dithiothreitol. The marked similarities between the two GTP-sensitive processes indicate that they may function via the same mechanism.