Calhoun B C, Lapierre L A, Chew C S, Goldenring J R
Institute for Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA.
Am J Physiol. 1998 Jul;275(1):C163-70. doi: 10.1152/ajpcell.1998.275.1.C163.
Previous investigations in several systems have demonstrated that Rab3 family members redistribute to soluble fractions on fusion of secretory granules with target plasma membranes. Rab proteins are then recycled back onto mature secretory vesicles after reinternalization of the membrane. Although this cycle is well established for Rab3, far less is known about redistribution of other Rab proteins during vesicle fusion and recycling. In the gastric parietal cell, Rab11a is associated with H-K-ATPase-containing tubulovesicles, which fuse with the apical plasma membrane (secretory canaliculus) in response to agonists such as histamine. We have analyzed distribution of Rab11a and other tubulovesicle proteins in resting and histamine-stimulated rabbit parietal cells. Stimulation of isolated gastric glands in the presence of 100 microM histamine and 100 microM 3-isobutyl-1-methylxanthine did not cause a significant increase in soluble Rab11a. H-K-ATPase, Rab11a, Rab25, syntaxin 3, and SCAMPs increased immunoreactivity in stimulus-associated vesicles prepared from rabbits treated with histamine compared with those from ranitidine-treated animals. The large GTPase dynamin was found in both vesicle preparations, but there was no change in amount of immunoreactivity. Immunofluorescence staining of resting and histamine-stimulated primary cultures of parietal cells demonstrated redistribution of H-K-ATPase and Rab11a to F-actin-rich canalicular membranes. Dynamin was present on canalicular membranes in resting and stimulated cells. These results indicate that Rab11a does not cycle off the membrane during the process of tubulovesicle fusion with the secretory canaliculus. Thus Rab11a may remain associated with recycling apical membrane vesicle populations.
先前在多个系统中的研究表明，在分泌颗粒与靶质膜融合时，Rab3家族成员会重新分布到可溶性部分。然后，在膜重新内化后，Rab蛋白会再循环回到成熟的分泌小泡上。虽然Rab3的这个循环已得到充分证实，但对于其他Rab蛋白在小泡融合和再循环过程中的重新分布了解得要少得多。在胃壁细胞中，Rab11a与含有H⁺-K⁺-ATP酶的微管泡相关，这些微管泡在组胺等激动剂的作用下与顶端质膜（分泌小管）融合。我们分析了静止和组胺刺激的兔胃壁细胞中Rab11a和其他微管泡蛋白的分布。在100微摩尔组胺和100微摩尔3-异丁基-1-甲基黄嘌呤存在的情况下刺激分离的胃腺，可溶性Rab11a没有显著增加。与雷尼替丁处理的动物相比，在用组胺处理的兔子制备的刺激相关小泡中，H⁺-K⁺-ATP酶、Rab11a、Rab25、 syntaxin 3和SCAMPs的免疫反应性增加。在两种小泡制剂中都发现了大GTP酶发动蛋白，但免疫反应性的量没有变化。对静止和组胺刺激的胃壁细胞原代培养物进行免疫荧光染色，结果表明H⁺-K⁺-ATP酶和Rab11a重新分布到富含F-肌动蛋白的小管膜上。在静止和受刺激的细胞中，发动蛋白都存在于小管膜上。这些结果表明，在微管泡与分泌小管融合的过程中，Rab11a不会从膜上循环下来。因此，Rab11a可能仍然与顶端膜小泡群体的再循环相关。
