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核苷二磷酸激酶 B 是形成含有 caveolae 的异三聚体 G 蛋白所必需的。

Nucleoside diphosphate kinase B is required for the formation of heterotrimeric G protein containing caveolae.

机构信息

Department of Internal Medicine III-Cardiology, University of Heidelberg, INF 410, 69120, Heidelberg, Germany.

出版信息

Naunyn Schmiedebergs Arch Pharmacol. 2011 Oct;384(4-5):461-72. doi: 10.1007/s00210-011-0618-x. Epub 2011 Mar 16.

Abstract

Caveolae are flask-shaped invaginations in the plasma membrane that serve to compartmentalize and organize signal transduction processes, including signals mediated by G protein-coupled receptors and heterotrimeric G proteins. Herein we report evidence for a close association of the nucleoside diphosphate kinase B (NDPK B) and caveolin proteins which is required for G protein scaffolding and caveolae formation. A concomitant loss of the proteins NDPK B, caveolin isoforms 1 (Cav1) and 3, and heterotrimeric G proteins occurred when one of these proteins was specifically depleted in zebrafish embryos. Co-immunoprecipitation of Cav1 with the G protein Gβ-subunit and NDPK B from zebrafish lysates corroborated the direct association of these proteins. Similarly, in embryonic fibroblasts from the respective knockout (KO) mice, the membrane content of the Cav1, Gβ, and NDPK B was found to be mutually dependent on one another. A redistribution of Cav1 and Gβ from the caveolae containing fractions of lower density to other membrane compartments with higher density could be detected by means of density gradient fractionation of membranes derived from NDPK A/B KO mouse embryonic fibroblasts (MEFs) and after shRNA-mediated NDPK B knockdown in H10 cardiomyocytes. This redistribution could be visualized by confocal microscopy analysis showing a decrease in the plasma membrane bound Cav1 in NDPK A/B KO cells and vice versa and a decrease in the plasma membrane pool of NDPK B in Cav1 KO cells. Consequently, ultrastructural analysis revealed a reduction of surface caveolae in the NDPK A/B KO cells. To prove that the disturbed subcellular localization of Cav1 in NDPK A/B KO MEFs as well as NDPK B in Cav1 KO MEFs is a result of the loss of NDPK B and Cav1, respectively, we performed rescue experiments. The adenoviral re-expression of NDPK B in NDPK A/B KO MEFs rescued the protein content and the plasma membrane localization of Cav1. The expression of an EGFP-Cav1 fusion protein in Cav1-KO cells induced a restoration of NDPK B expression levels and its appearance at the plasma membrane. We conclude from these findings that NDPK B, heterotrimeric G proteins, and caveolins are mutually dependent on each other for stabile localization and caveolae formation at the plasma membrane. The data point to a disturbed transport of caveolin/G protein/NDPK B complexes from intracellular membrane compartments if one of the components is missing.

摘要

小窝是质膜中的烧瓶状内陷,用于分隔和组织信号转导过程,包括 G 蛋白偶联受体和异三聚体 G 蛋白介导的信号。在此,我们报告了核苷二磷酸激酶 B(NDPK B)和 caveolin 蛋白之间密切相关的证据,这对于 G 蛋白支架和 caveolae 的形成是必需的。当这些蛋白中的一种在斑马鱼胚胎中被特异性耗尽时,会同时丢失蛋白 NDPK B、Cav1 同工型 1(Cav1)和 3,以及异三聚体 G 蛋白。来自斑马鱼裂解物的 Cav1 与 G 蛋白 Gβ-亚基和 NDPK B 的共免疫沉淀证实了这些蛋白的直接关联。同样,在各自的敲除(KO)小鼠的胚胎成纤维细胞中,膜中 Cav1、Gβ 和 NDPK B 的含量彼此相互依赖。通过密度梯度分离 NDPK A/B KO 鼠胚胎成纤维细胞(MEF)衍生的膜,可以检测到 Cav1 和 Gβ 从富含低密度 caveolae 的部分到具有更高密度的其他膜隔室的再分配,并且在 H10 心肌细胞中通过 shRNA 介导的 NDPK B 敲低后也可以检测到这种再分配。通过共聚焦显微镜分析可以观察到这种再分配,结果显示在 NDPK A/B KO 细胞中 Cav1 与质膜结合减少,反之亦然,在 Cav1 KO 细胞中 NDPK B 的质膜池减少。因此,超微结构分析显示 NDPK A/B KO 细胞中的表面 caveolae 减少。为了证明 NDPK A/B KO MEF 中 Cav1 和 Cav1 KO MEF 中 NDPK B 的亚细胞定位紊乱分别是由于 NDPK B 和 Cav1 的缺失,我们进行了挽救实验。在 NDPK A/B KO MEF 中,腺病毒再表达 NDPK B 可挽救 Cav1 的蛋白含量和质膜定位。在 Cav1-KO 细胞中表达 EGFP-Cav1 融合蛋白可诱导 NDPK B 表达水平及其在质膜上的出现恢复。从这些发现中我们得出结论,NDPK B、异三聚体 G 蛋白和 caveolins 相互依赖于彼此以稳定定位并在质膜上形成 caveolae。如果其中一个成分缺失,数据表明 caveolin/G 蛋白/NDPK B 复合物的运输受到干扰。

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