Molecular cloning and characterization of a novel carboxylesterase-like protein that is physiologically present at high concentrations in the urine of domestic cats (Felis catus)
Molecular cloning and characterization of a novel carboxylesterase-like protein that is physiologically present at high concentrations in the urine of domestic cats (Felis catus)
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DOI：
10.1042/bj20021446
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发表时间：
2003-02-15
影响因子：
4.1
通讯作者：
Yamashita, T
中科院分区：
文献类型：
--
作者：
Miyazaki, M;Kamiie, K;Yamashita, T
正常的哺乳动物通常只在尿液中排泄少量的蛋白质，从而避免蛋白质从体内大量泄漏。蛋白尿是肾脏疾病中最常见的异常。然而，健康的家猫（Felis catits）在尿液中排出高浓度（约0.5 mg/ml）的蛋白质。我们研究了健康猫蛋白尿的可能原因，发现了一种70 kDa的糖蛋白，它作为猫尿中的主要尿蛋白排泄，与性别无关。为了阐明该蛋白的生化功能和排泄机制，我们从猫肾cDNA文库中克隆了该蛋白的cDNA。推导的氨基酸序列与大鼠肝羧酸酯酶（EC 3.1.1.1）的氨基酸序列同源性为47%，丝氨酸水解酶活性位点和羧酸酯酶特异性序列均保守。因此我们将这种蛋白质命名为cauxin（羧酸酯酶样尿排泄蛋白）。与哺乳动物的羧酸酯酶不同，大多数羧酸酯酶位于各种器官的细胞内，可可生长素特异性地表达于远端小管的上皮细胞中，并有效地分泌到尿液中，这可能是因为它缺乏内质网滞留序列（HDEL）。基于我们的发现，在未成熟的猫肾中不表达，我们得出结论，生长素参与的生理功能是特定的成熟的猫。最近，在人脑和畸胎瘤细胞中发现了类cauxin-like cDNA。这些数据表明，cauxin和cauxin-like人类蛋白被归类为一个新的组羧酸酯酶多基因家族。
Normal mammals generally excrete only small amounts of protein in the urine, thus avoiding major leakage of proteins from the body. Proteinuria is the most commonly recognized abnormality in renal disease. However, healthy domestic cats (Felis catits) excrete proteins at high concentrations (about 0.5 mg/ml) in their urine. We investigated the possible cause of proteinuria in healthy cats, and discovered a 70 kDa glycoprotein, which was excreted as a major urinary protein in cat urine, irrespective of gender. To elucidate the biochemical functions and the excretion mechanism of this protein, we cloned the cDNA for this protein from a cat kidney cDNA library. The deduced amino acid sequence shared 47 % identity with the rat liver carboxylesterase (EC 3.1.1.1), and both the serine hydrolase active site and the carboxylesterase-specific sequence were conserved. Therefore we named this protein cauxin (carboxylesterase-like urinary excreted protein). In contrast to the mammalian carboxylesterases, most of which are localized within the cells of various organs, cauxin was expressed specifically in the epithelial cells of the distal tubules, and was secreted efficiently into the urine, probably because it lacked the endoplasmic reticulum retention sequence (HDEL). Based on our finding that cauxin is not expressed in the immature cat kidney, we conclude that cauxin is involved in physiological functions that are specific for mature cats. Recently, cauxin-like cDNAs were found from human brain and teratocarcinoma cells. These data suggest that cauxin and cauxin-like human proteins are categorized as a novel group of carboxylesterase multigene family.