Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
Acta Histochem Cytochem. 2012 Dec 26;45(6):317-23. doi: 10.1267/ahc.12014. Epub 2012 Nov 3.
Rab20 is a member of the Rab GTPase family, but its implication in macropinocytosis is unclear. We examined the spatiotemporal localization of Rab20 in RAW264 macrophages by the live-cell imaging of fluorescent protein-fused Rab20. It was shown that Rab20 was transiently associated with macropinosomal membranes. During the early stage of macropinosome formation, Rab20 was slightly localized on the circular ruffles (macropinocytic cups), the precursor forms of macropinosomes, and was increasingly recruited to the newly formed macropinosomes. Although Rab20 was colocalized with Rab5 and Rab21 on macropinosomal membranes, the association of Rab20 with macropinosomes persisted even after the dissociations of Rab5 and Rab21 from macropinosomal membranes. Rab20 was then colocalized with Rab7 and Lamp1, late endosomal/lysosomal markers, on macropinosomes for a while. Our data indicate that Rab20 is a novel component of macropinocytic pathway and functions at long-standing stages from early to late macropinosome maturation.
Rab20 是 Rab GTPase 家族的成员，但它在胞吞作用中的作用尚不清楚。我们通过荧光蛋白融合 Rab20 的活细胞成像来检测 RAW264 巨噬细胞中 Rab20 的时空定位。结果表明，Rab20 与大胞饮泡（胞饮杯）的质膜短暂相关，大胞饮泡是大胞饮作用的前体形式，并且越来越多地募集到新形成的大胞饮泡。尽管 Rab20 与 Rab5 和 Rab21 在大胞饮泡的质膜上共定位，但 Rab20 与大胞饮泡的结合在 Rab5 和 Rab21 从大胞饮泡的质膜解离后仍然存在。随后，Rab20 与晚期内体/溶酶体标志物 Rab7 和 Lamp1 共定位在大胞饮泡上一段时间。我们的数据表明，Rab20 是大胞饮作用途径的一个新组成部分，在大胞饮泡从早期到晚期成熟的长期阶段发挥作用。
