Williams Siân E, Reed Anita A C, Galvanovskis Juris, Antignac Corinne, Goodship Tim, Karet Fiona E, Kotanko Peter, Lhotta Karl, Morinière Vincent, Williams Paul, Wong William, Rorsman Patrik, Thakker Rajesh V
Academic Endocrine Unit, Churchill Hospital, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Headington, Oxford OX3 7LJ, UK.
Hum Mol Genet. 2009 Aug 15;18(16):2963-74. doi: 10.1093/hmg/ddp235. Epub 2009 May 22.
Familial juvenile hyperuricaemic nephropathy (FJHN), an autosomal dominant disorder, is caused by mutations in the UMOD gene, which encodes Uromodulin, a glycosylphosphatidylinositol-anchored protein that is expressed in the thick ascending limb of the loop of Henle and excreted in the urine. Uromodulin contains three epidermal growth factor (EGF)-like domains, a cysteine-rich region which includes a domain of eight cysteines and a zona pellucida (ZP) domain. Over 90% of UMOD mutations are missense, and 62% alter a cysteine residue, implicating a role for protein misfolding in the disease. We investigated 20 northern European FJHN probands for UMOD mutations. Wild-type and mutant Uromodulins were functionally studied by expression in HeLa cells and by the use of western blot analysis and confocal microscopy. Six different UMOD missense mutations (Cys32Trp, Arg185Gly, Asp196Asn, Cys217Trp, Cys223Arg and Gly488Arg) were identified. Patients with UMOD mutations were phenotypically similar to those without UMOD mutations. The mutant Uromodulins had significantly delayed maturation, retention in the endoplasmic reticulum (ER) and reduced expression at the plasma membrane. However, Gly488Arg, which is the only mutation we identified in the ZP domain, was found to be associated with milder in vitro abnormalities and to be the only mutant Uromodulin detected in conditioned medium from transfected cells, indicating that the severity of the mutant phenotypes may depend on their location within the protein. Thus, FJHN-causing Uromodulin mutants are retained in the ER, with impaired intracellular maturation and trafficking, thereby indicating mechanisms whereby Uromodulin mutants may cause the phenotype of FJHN.
家族性青少年高尿酸血症肾病（FJHN）是一种常染色体显性疾病，由UMOD基因突变引起，该基因编码尿调节蛋白，这是一种糖基磷脂酰肌醇锚定蛋白，在髓袢升支粗段表达并随尿液排出。尿调节蛋白包含三个表皮生长因子（EGF）样结构域、一个富含半胱氨酸的区域（包括一个由八个半胱氨酸组成的结构域）和一个透明带（ZP）结构域。超过90%的UMOD突变是错义突变，62%的突变改变了半胱氨酸残基，这表明蛋白质错误折叠在该疾病中起作用。我们对20名北欧FJHN先证者进行了UMOD基因突变检测。通过在HeLa细胞中表达、使用蛋白质印迹分析和共聚焦显微镜对野生型和突变型尿调节蛋白进行了功能研究。鉴定出六种不同的UMOD错义突变（Cys32Trp、Arg185Gly、Asp196Asn、Cys217Trp、Cys223Arg和Gly488Arg）。携带UMOD突变的患者在表型上与未携带UMOD突变的患者相似。突变型尿调节蛋白的成熟明显延迟，滞留在内质网（ER）中，并且在质膜上的表达减少。然而，Gly488Arg是我们在ZP结构域中鉴定出的唯一突变，发现它与体外较轻的异常有关，并且是在转染细胞的条件培养基中检测到的唯一突变型尿调节蛋白，这表明突变表型的严重程度可能取决于它们在蛋白质中的位置。因此，导致FJHN的尿调节蛋白突变体滞留在内质网中，细胞内成熟和运输受损，从而揭示了尿调节蛋白突变体可能导致FJHN表型的机制。
