Fiedler K, Lafont F, Parton R G, Simons K
Cell Biology Programme, European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
J Cell Biol. 1995 Mar;128(6):1043-53. doi: 10.1083/jcb.128.6.1043.
The sorting of apical and basolateral proteins into vesicular carriers takes place in the trans-Golgi network (TGN) in MDCK cells. We have previously analyzed the protein composition of immunoisolated apical and basolateral transport vesicles and have now identified a component that is highly enriched in apical vesicles. Isolation of the encoding cDNA revealed that this protein, annexin XIIIb, is a new isoform of the epithelial specific annexin XIII sub-family which includes the previously described intestine-specific annexin (annexin XIIIa; Wice, B. M., and J. I. Gordon. 1992. J. Cell Biol. 116:405-422). Annexin XIIIb differs from annexin XIIIa in that it contains a unique insert of 41 amino acids in the NH2 terminus and is exclusively expressed in dog intestine and kidney. Immunofluorescence microscopy demonstrated that annexin XIIIb was localized to the apical plasma membrane and underlying punctate structures. Since annexins have been suggested to play a role in membrane-membrane interactions in exocytosis and endocytosis, we investigated whether annexin XIIIb is involved in delivery to the apical cell surface. To this aim we used permeabilized MDCK cells and a cytosol-dependent in vitro transport assay. Antibodies specific for annexin XIIIb significantly inhibited the transport of influenza virus hemagglutinin from the TGN to the apical plasma membrane while the transport of vesicular stomatitis virus glycoprotein to the basolateral cell surface was unaffected. We propose that annexin XIIIb plays a role in vesicular transport to the apical plasma membrane in MDCK cells.
在MDCK细胞中，顶端和基底外侧蛋白被分选到囊泡载体的过程发生在反式高尔基体网络（TGN）中。我们之前分析了免疫分离的顶端和基底外侧运输囊泡的蛋白质组成，现在鉴定出一种在顶端囊泡中高度富集的成分。对编码cDNA的分离显示，这种蛋白质，即膜联蛋白XIIIb，是上皮特异性膜联蛋白XIII亚家族的一种新亚型，该亚家族包括先前描述的肠道特异性膜联蛋白（膜联蛋白XIIIa；Wice, B. M., 和J. I. Gordon. 1992. J. Cell Biol. 116:405 - 422）。膜联蛋白XIIIb与膜联蛋白XIIIa的不同之处在于，它在NH2末端含有一个独特的41个氨基酸的插入序列，并且仅在犬类肠道和肾脏中表达。免疫荧光显微镜检查表明，膜联蛋白XIIIb定位于顶端质膜和下面的点状结构。由于膜联蛋白被认为在胞吐作用和胞吞作用的膜 - 膜相互作用中发挥作用，我们研究了膜联蛋白XIIIb是否参与向顶端细胞表面的转运。为此，我们使用了通透的MDCK细胞和一种依赖胞质溶胶的体外转运测定法。针对膜联蛋白XIIIb的特异性抗体显著抑制了流感病毒血凝素从TGN向顶端质膜的转运，而水疱性口炎病毒糖蛋白向基底外侧细胞表面的转运则不受影响。我们提出，膜联蛋白XIIIb在MDCK细胞中向顶端质膜的囊泡转运中发挥作用。
