Nagano F, Orita S, Sasaki T, Naito A, Sakaguchi G, Maeda M, Watanabe T, Kominami E, Uchiyama Y, Takai Y
Department of Molecular Biology and Biochemistry, University Medical School, Suita, Japan.
J Biol Chem. 1998 Nov 13;273(46):30065-8. doi: 10.1074/jbc.273.46.30065.
Doc2 has one Munc13-interacting domain at the N-terminal region and two C2-like domains interacting with Ca2+ and phospholipid at the C-terminal region. Doc2 consists of two isoforms, Doc2alpha and -beta. Doc2alpha is specifically expressed in neuronal cells and implicated in Ca2+-dependent neurotransmitter release, whereas Doc2beta is ubiquitously expressed and its function is unknown. We show here that both Doc2alpha and -beta interact with rat tctex-1, a light chain of cytoplasmic dynein, in both cell-free and intact cell systems. Overexpression of the N-terminal fragment of Doc2 containing the tctex-1-interacting domain induces changes in the intracellular localization of cation-independent mannose 6-phosphate receptor and its ligand, cathepsin D, which are transported from trans-Golgi network to late endosomes. Overexpression of the C-terminal fragment containing two C2-like domains shows the similar effect, but to a lesser extent, whereas overexpression of full-length Doc2 or the C-terminal fragment of rabphilin3 containing two C2-like domains does not show this effect. Because dynein is a minus-end-directed microtubule-based motor protein, these results suggest that Doc2, especially Doc2beta, plays a role in dynein-dependent intracellular vesicle transport.
Doc2在其N端区域有一个与Munc13相互作用的结构域，在C端区域有两个与Ca2+和磷脂相互作用的C2样结构域。Doc2由两种亚型组成，即Doc2α和Doc2β。Doc2α在神经元细胞中特异性表达，并参与Ca2+依赖的神经递质释放，而Doc2β在全身广泛表达，其功能尚不清楚。我们在此表明，在无细胞和完整细胞系统中，Doc2α和Doc2β均与大鼠tctex-1（一种胞质动力蛋白轻链）相互作用。包含与tctex-1相互作用结构域的Doc2 N端片段的过表达会诱导非依赖阳离子的甘露糖6-磷酸受体及其配体组织蛋白酶D的细胞内定位发生变化，它们从反式高尔基体网络转运至晚期内体。包含两个C2样结构域的C端片段的过表达显示出类似的效果，但程度较小，而全长Doc2或包含两个C2样结构域的rabphilin3 C端片段的过表达则未显示出这种效果。由于动力蛋白是一种基于微管的负端定向运动蛋白，这些结果表明Doc2，尤其是Doc2β，在动力蛋白依赖的细胞内囊泡运输中发挥作用。
