Komada M, Kitamura N
Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan.
Biochem Biophys Res Commun. 2001 Mar;281(5):1065-9. doi: 10.1006/bbrc.2001.4441.
The molecular mechanisms of endocytosis and exocytosis are not yet fully understood. Hrs and Hbp, two tightly associated proteins in eukaryotic cells, have been implicated in these cellular processes. Hrs is homologous to Vps27p, an endosomal protein required for vacuolar and endocytic trafficking in yeast. Hrs is localized to early endosomes and is required for the normal morphology of early endosomes in mammalian cells. Hrs also associates with proteins implicated in endocytosis and exocytosis such as SNAP-25 and Eps15. Hrs treatment inhibits neurotransmitter release in permeabilized neuronal cells and its overexpression inhibits internalization of transferrin. Overexpression of dominant-negative Hbp mutants inhibits ligand-induced downregulation of growth factor/receptor complexes and immunoglobulin E receptor-triggered degranulation of secretory granules in mast cells. These observations suggest an important role for the Hrs/Hbp protein complex in vesicular trafficking during endocytosis and exocytosis.
内吞作用和外排作用的分子机制尚未完全明确。Hrs和Hbp是真核细胞中紧密相关的两种蛋白质，它们与这些细胞过程有关。Hrs与Vps27p同源，Vps27p是酵母中液泡和内吞运输所需的一种内体蛋白。Hrs定位于早期内体，是哺乳动物细胞早期内体正常形态所必需的。Hrs还与参与内吞作用和外排作用的蛋白质相关，如SNAP - 25和Eps15。Hrs处理可抑制通透化神经元细胞中神经递质的释放，其过表达可抑制转铁蛋白的内化。显性负性Hbp突变体的过表达可抑制配体诱导的生长因子/受体复合物的下调以及肥大细胞中免疫球蛋白E受体触发的分泌颗粒脱颗粒。这些观察结果表明Hrs/Hbp蛋白复合物在内吞作用和外排作用期间的囊泡运输中起重要作用。
