Provost P R, Weech P K, Tremblay N M, Marcel Y L, Rassart E
Département des Sciences Biologiques, Université du Québec à Montréal, Canada.
J Lipid Res. 1990 Nov;31(11):2057-65.
We report for the first time the quantification of relative apolipoprotein D (apoD) mRNA concentrations in a wide selection of organs and a detailed characterization of the rabbit protein. ApoD cDNA clones were isolated from a rabbit testis cDNA library by screening with a human apoD cDNA-derived RNA probe. The 912 nucleotide sequence of rabbit apoD cDNA contains a unique reading frame coding for a protein sharing 80% homology with human apoD. The two sequences have two potential asparagine-linked glycosylation sites at the same positions, almost superimposable hydrophobicity plot, and the antigenic proteins show similar charge polymorphism, Mr, and lipoprotein distribution. This high degree of similarity shows that the rabbit system can be used as a model for apoD studies. Moreover, the two consensus sequences of the hydrophobic ligand carrier (alpha 2-microglobulin) family present in human apoD are also found in the rabbit protein and these sequences coincide with the most conserved regions. The distribution of apoD mRNA among rabbit organs was determined by Northern blot and quantitative dot blot analysis. The highest levels of mRNA were found in spleen, adrenal glands, lungs, brain, testis, and kidneys. Moderate or low concentrations were detected in all the other organs tested including liver and small intestine. Thus, our results show that the apoD gene is expressed mainly in peripheral organs, with levels as high as 59-fold that of the liver, unlike other apolipoproteins. We suggest that apoD exerts its main function locally in peripheral organs.
我们首次报道了在多种器官中相对载脂蛋白D（apoD）mRNA浓度的定量分析以及兔蛋白的详细特征。通过用人apoD cDNA衍生的RNA探针筛选，从兔睾丸cDNA文库中分离出apoD cDNA克隆。兔apoD cDNA的912个核苷酸序列包含一个独特的阅读框，编码一种与人类apoD具有80%同源性的蛋白质。这两个序列在相同位置有两个潜在的天冬酰胺连接糖基化位点，疏水图谱几乎重叠，抗原蛋白显示出相似的电荷多态性、相对分子质量（Mr）和脂蛋白分布。这种高度相似性表明兔系统可作为apoD研究的模型。此外，在人类apoD中存在的疏水配体载体（α2-微球蛋白）家族的两个共有序列在兔蛋白中也有发现，且这些序列与最保守区域一致。通过Northern印迹和定量斑点印迹分析确定了apoD mRNA在兔器官中的分布。在脾脏、肾上腺、肺、脑、睾丸和肾脏中发现了最高水平的mRNA。在包括肝脏和小肠在内的所有其他测试器官中检测到中等或低浓度。因此，我们的结果表明，与其他载脂蛋白不同，apoD基因主要在外周器官中表达，其水平高达肝脏的59倍。我们认为apoD在外周器官中发挥其主要局部功能。
