Secretory vesicle swelling by atomic force microscopy.
Secretory vesicle swelling by atomic force microscopy.
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通过原子力显微镜观察分泌囊泡肿胀。
DOI：
10.1007/978-1-59259-993-6_16
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Jena,BhanuP
中科院分区：
文献类型：
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作者：
Cho,Sang-Joon;Jena,BhanuP
分泌囊泡的肿胀与胞吐有关，但囊泡肿胀的潜在机制尚不清楚。我们实验室早期的研究证实了异三聚体gtp结合蛋白G±i3 α-亚基与酶原颗粒膜的关联，并暗示其参与囊泡肿胀。Mas7，一种已知能刺激Gi蛋白的活性乳突蛋白类似物，被发现能刺激分离的酶原颗粒的GTPase活性并引起肿胀。GTP、NaF和Mas7存在时囊泡大小的增加是不可逆的，并且对KCl敏感。Ca2+对酶原颗粒大小无影响。综上所述，这些结果表明胰腺外分泌的酶原颗粒（膜结合的分泌囊）在G±i3蛋白介导的GTP作用下膨胀。随后，我们的研究表明，水通道水通道蛋白-1 （AQP1）也存在于酶原颗粒膜上，并参与gtp诱导和G±i3介导的囊泡水门控和肿胀。分离的酵素颗粒表现出较低的基础水渗透率。然而，颗粒暴露于GTP导致水进入的显著增强。用已知的水通道抑制剂Hg2+处理酶原颗粒会导致基础和gtp刺激的水进入和囊泡肿胀的可逆性损失。引入针对AQP1羧基末端结构域的AQP1特异性抗体，可阻断gtp刺激的囊泡肿胀。我们的研究结果表明，与酶原颗粒膜相关的AQP1参与了基础gtp诱导和G±i3介导的水进入外分泌胰腺酶原颗粒的快速门控。
The swelling of secretory vesicles has been implicated in exocytosis, but the underlying mechanism of vesicle swelling remained unknown. Earlier studies from our laboratory demonstrated the association of the α-subunit of heterotrimeric GTP-binding protein G±i3with zymogen granule membrane and implicated its involvement in vesicle swelling. Mas7, an active mastoparan analog known to stimulate Gi proteins, was found to stimulate the GTPase activity of isolated zymogen granules and cause swelling. Increase in vesicle size in the presence of GTP, NaF, and Mas7 were irreversible and found to be KCl sensitive. However, Ca2+had no effect on zymogen granule size. Taken together, these results indicated that zymogen granules, the membrane-bound secretory vesicles in exocrine pancreas, swell in response to GTP mediated by a G±i3protein. Subsequently, our studies demonstrated that the water channel aquaporin-1 (AQP1) is also present at the zymogen granule membrane and participates in rapid GTP-induced and G±i3-mediated vesicular water gating and swelling. Isolated zymogen granules exhibit low basal water permeability. However, exposure of granules to GTP results in a marked potentiation of water entry. Treatment of zymogen granules with the known water channel inhibitor Hg2+is accompanied by a reversible loss in both the basal and GTP-stimulable water entry and vesicle swelling. Introduction of AQP1-specific antibody raised against the carboxy-terminal domain of AQP1 blocked GTP-stimulable swelling of vesicles. Our results demonstrate that AQP1 associated at the zymogen granule membrane is involved in basal GTP-induced and G±i3-mediated rapid gating of water into zymogen granules of the exocrine pancreas.