Langford T Dianne, Silberman Jeffrey D, Weiland Malin E-L, Svärd Staffan G, McCaffery J Michael, Sogin Mitchell L, Gillin Frances D
Division of Infectious Diseases, Department of Pathology, University of California, San Diego, CA 92103-8416, USA.
Exp Parasitol. 2002 May;101(1):13-24. doi: 10.1016/s0014-4894(02)00037-1.
To investigate the complexity of the endomembrane transport system in the early diverging eukaryote, Giardia lamblia, we characterized homologues of the GTP-binding proteins, Rab1 and Rab2, involved in regulating vesicular trafficking between the endoplasmic reticulum and Golgi in higher eukaryotes, and GDI, which plays a key role in the cycling of Rab proteins. G. lamblia Rab1, 2.1, and GDI sequences largely resemble yeast and mammalian homologues, are transcribed as 0.66-, 0.62-, and 1.4-kb messages, respectively, and are expressed during growth and encystation. Western analyses detected an abundant Rab/GDI complex at approximately 80 kDa, and free GDI (60 kDa) in both trophozoites and encysting cells. Immunoelectron microscopy with antibody to Rab1 localized Rab with ER, encystation secretory vesicles, and lysosome-like peripheral vesicles. GDI associated with these structures, and with small vesicles found throughout the cytoplasm, consistent with GDI's key role in Rab cycling between organelles within the cell.
为了研究早期分化的真核生物蓝氏贾第鞭毛虫内膜运输系统的复杂性，我们对参与调节高等真核生物内质网和高尔基体之间囊泡运输的GTP结合蛋白Rab1和Rab2的同源物，以及在Rab蛋白循环中起关键作用的GDI进行了表征。蓝氏贾第鞭毛虫Rab1、2.1和GDI序列在很大程度上类似于酵母和哺乳动物的同源物，分别转录为0.66kb、0.62kb和1.4kb的信使RNA，并在生长和包囊化过程中表达。蛋白质免疫印迹分析在滋养体和包囊化细胞中均检测到约80kDa的丰富Rab/GDI复合物和游离GDI（60kDa）。用抗Rab1抗体进行免疫电子显微镜观察，发现Rab定位于内质网、包囊化分泌囊泡和溶酶体样外周囊泡。GDI与这些结构以及整个细胞质中发现的小囊泡相关，这与GDI在细胞内细胞器之间Rab循环中的关键作用一致。
