NUCLEAR-PORE COMPLEX CONTAINS A FAMILY OF GLYCOPROTEINS THAT INCLUDES P62 - GLYCOSYLATION THROUGH A PREVIOUSLY UNIDENTIFIED CELLULAR PATHWAY
NUCLEAR-PORE COMPLEX CONTAINS A FAMILY OF GLYCOPROTEINS THAT INCLUDES P62 - GLYCOSYLATION THROUGH A PREVIOUSLY UNIDENTIFIED CELLULAR PATHWAY
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DOI：
10.1073/pnas.84.21.7552
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发表时间：
1987-11-01
影响因子：
11.1
通讯作者：
BLOBEL, G
中科院分区：
文献类型：
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作者：
DAVIS, LI;BLOBEL, G
我们先前利用一种单克隆抗体（mAb 414）鉴定出一种62 kDa的蛋白质（p62），通过免疫电子显微镜观察，其定位于核孔复合体。我们还表明p62能特异性结合麦胚凝集素。因此，我们提出这种核孔复合体蛋白质可能是一个近期被鉴定的糖蛋白家族的成员，该家族可通过大鼠肝细胞核的体外半乳糖基化进行标记，且含有O -连接的单糖N -乙酰葡糖胺（GlcNAc）残基。为支持这一观点，我们现在表明，由于末端GlcNAc残基的去除，与N -乙酰葡糖胺糖苷酶一起孵育可使p62的分子量降低约3 kDa。此外，利用UDP - [³H]半乳糖和半乳糖基转移酶，p62可在体外进行半乳糖基化。我们还表明，当p62可溶且位于胞质时，大部分GlcNAc残基在合成后的5分钟内添加。因此，GlcNAc的添加在细胞质中进行，且明显不同于内质网和高尔基体的N -连接和O -连接糖基化途径。利用另一种对含核GlcNAc蛋白质具有广泛特异性的单克隆抗体，通过免疫荧光和亚核组分的蛋白质印迹，我们表明这些蛋白质中的一些位于细胞核内部，而其他的很可能位于核孔复合体。
Using a monoclonal antibody (mAb 414), we previously identified a protein of 62 kDa (p62) that was localized to the nuclear pore complex by immunoelectron microscopy. We also showed that p62 binds specifically to wheat germ agglutinin. Therefore, we proposed that this nuclear pore complex protein might be a member of a recently characterized family of glycoproteins that are labeled by in vitro galactosylation of rat liver nuclei and contain O-linked monosaccharide GlcNAc residues. In support of this, we now show that incubation with N-acetylglucosaminidase reduces the molecular mass of p62 by .apprxeq. 3 kDa because of the removal of terminal GlcNAc residues. Moreover, p62 can be galactosylated in vitro by using UDP-[3H]galactose and galactosyltransferase. We also show that most of the GlcNAc residues are added within 5 min of synthesis, when p62 is soluble and cytosolic. Thus, the addition of GlcNAc is carried out in the cytoplasm and is clearly distinct from the N- and O-linked glycosylation pathways of the endoplasmic reticulum and Golgi complex. Using another mAb with a broad specificity for nuclear GlcNAc-containing proteins, we show by immunofluorescence and protein blotting of subnuclear fractions that some of these proteins are in the interior of the nucleus, and others are most likely located in the pore complex.