Nashida Tomoko, Imai Akane, Shimomura Hiromi
Department of Biochemistry, School of Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Niigata 951-8580, Japan.
Arch Oral Biol. 2006 Feb;51(2):89-95. doi: 10.1016/j.archoralbio.2005.06.005. Epub 2005 Aug 1.
Amylase secretion from rat parotid acinar cells is induced by the accumulation of cAMP in response to beta-adrenergic agonists as well as by the elevation of intracellular Ca2+ in response to muscarinic cholinergic stimulation. Several proteins including the low molecular weight GTP-binding protein Rab may participate in these exocytic processes. In the current studies, we investigated the role of Rab26 in the process of amylase secretion. Secretory granules were separated by centrifugation on a Percoll-sucrose density gradient into mature and immature granule fractions. Rab26 and two other type III Rab proteins, Rab3D and Rab27, were present in the mature granule membrane fraction. Also, Rab26 was absent in immature granule membrane fractions. Isoproterenol-induced amylase release from streptolysin-O-permeabilised acinar cells was inhibited by an anti-Rab26 antibody, but this antibody had no effect on the Ca2+-induced release of amylase. Finally, in the early stage of beta-adrenergic stimulation, Rab26 was condensed in the secretory granule membrane. These results indicate that Rab26 is involved in the recruitment of mature granules to the plasma membrane upon beta-adrenergic stimulation.
大鼠腮腺腺泡细胞的淀粉酶分泌可由β-肾上腺素能激动剂刺激导致的环磷酸腺苷（cAMP）积累所诱导，也可由毒蕈碱胆碱能刺激引起的细胞内钙离子（Ca2+）浓度升高所诱导。包括低分子量GTP结合蛋白Rab在内的几种蛋白质可能参与这些胞吐过程。在当前研究中，我们研究了Rab26在淀粉酶分泌过程中的作用。通过在Percoll-蔗糖密度梯度上离心，将分泌颗粒分离为成熟和未成熟颗粒组分。Rab26以及另外两种III型Rab蛋白Rab3D和Rab27存在于成熟颗粒膜组分中。此外，未成熟颗粒膜组分中不存在Rab26。抗Rab26抗体抑制了异丙肾上腺素诱导的链霉溶菌素-O通透的腺泡细胞淀粉酶释放，但该抗体对钙离子诱导的淀粉酶释放没有影响。最后，在β-肾上腺素能刺激的早期阶段，Rab26聚集在分泌颗粒膜中。这些结果表明Rab26参与了β-肾上腺素能刺激时成熟颗粒向质膜的募集过程。
