Rab3D, a small GTPase, is localized on mast cell secretory granules and translocates to the plasma membrane upon exocytosis.
Rab3D, a small GTPase, is localized on mast cell secretory granules and translocates to the plasma membrane upon exocytosis.
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DOI：
10.1165/ajrcmb.20.1.3279
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发表时间：
1999
影响因子：
6.4
通讯作者：
M. Tuvim;Roberto Adachi;J. F. Chocano;Robert H. Moore;Robert M. Lampert;E. Zera;Elkin Romero;B. J. Knoll;B. Dickey
中科院分区：
文献类型：
--
作者：
M. Tuvim;Roberto Adachi;J. F. Chocano;Robert H. Moore;Robert M. Lampert;E. Zera;Elkin Romero;B. J. Knoll;B. Dickey
尽管肥大细胞分泌因其在过敏反应中的关键作用和作为生理模型的优势而被广泛研究，但肥大细胞分泌机器的分子组成几乎是未知的。鉴于肥大细胞胞吐的鸟嘌呤核苷酸依赖性和Rab3蛋白参与突触小泡的释放，我们假设Rab3亚型调节肥大细胞的分泌。通过逆转录聚合酶链式反应(RT-PCR)从RBL-2H3肥大细胞中克隆了Rab3A、3B和3D基因片段。Northern印迹分析表明，Rab3D的转录本相对丰富，Rab3B的转录本相对较少，Rab3A和3C的转录本无法检测到。通过核糖核酸酶(RNase)保护分析，Rab3D转录本的丰度至少是其他异构体的10倍，通过免疫印迹分析，Rab3D蛋白的丰度至少是Rab3B的60倍。Rab3D在RBL细胞中的表达比在脑中丰富，但在RBL细胞中的总蛋白质量比在脑中少10倍。Rab3D仅在RBL细胞中部分与分泌颗粒共定位，而在成熟的腹膜肥大细胞中完全共定位。静息状态下肥大细胞中Rab3D的浓度梯度由外周向中央递减，未检测到胞浆池。在胞吐脱颗粒后，Rab3D移位到质膜上，并在那里停留至少15分钟。这些研究表明，Rab3D是肥大细胞调控的胞吐机制的一个组成部分，并确定了肥大细胞和神经元在Rab3表达和运输方面的差异。
Although mast cell secretion has been intensively studied because of its pivotal role in allergic reactions and its advantages as a physiologic model, the molecular composition of the secretory machine is virtually unknown. In view of the guanine-nucleotide dependency of mast cell exocytosis and the participation of Rab3 proteins in synaptic vesicle release, we hypothesized that a Rab3 isoform regulates mast cell secretion. Fragments of Rab3A, 3B, and 3D were cloned from RBL-2H3 mast cells by reverse transcription- polymerase chain reaction (RT-PCR). Northern blot analysis revealed Rab3D transcripts to be relatively abundant, Rab3B substantially less so, and Rab3A and 3C undetectable. By ribonuclease (RNase) protection assay, Rab3D transcripts were at least 10-fold more abundant than those of other isoforms, and by immunoblot analysis, Rab3D protein was at least 60-fold more abundant than that of Rab3B. Rab3D was more abundant in RBL cells than in brain, but the total mass of Rab3 proteins in RBL cells was 10-fold less than in brain. Rab3D only partly colocalized with secretory granules in RBL cells, but fully colocalized in mature peritoneal mast cells. There was a descending concentration gradient of Rab3D from peripheral to central granules, and no cytoplasmic pool was detectable in resting mast cells. Following exocytotic degranulation, Rab3D translocated to the plasma membrane and remained there for at least 15 min. These studies suggest that Rab3D is a component of the regulated exocytotic machine of mast cells, and identify differences between mast cells and neurons in Rab3 expression and trafficking.