Multiple epiphyseal dysplasia mutations in MATN3 cause misfolding of the A-domain and prevent secretion of mutant matrilin-3
Multiple epiphyseal dysplasia mutations in MATN3 cause misfolding of the A-domain and prevent secretion of mutant matrilin-3
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DOI：
10.1002/humu.20263
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发表时间：
2005-12-01
期刊：
影响因子：
3.9
通讯作者：
Briggs, MD
中科院分区：
文献类型：
--
作者：
Cotterill, SL;Jackson, GC;Briggs, MD
多发性骨骺发育不良(MED)是一种相对常见的骨骼发育不良，可在儿童时期表现为身材矮小、大关节疼痛和僵硬等不同表型，成年后常进展为早发性骨关节炎。Matrlin-3基因(MATN3)的突变最近被证明是某些形式的常染色体显性遗传性MED的基础。到目前为止，Matrlin-3的所有MED突变都位于单个A结构域，表明它们可能破坏这个重要结构域的结构和/或功能。为了确定MATN3突变对matrlin-3结构和功能的影响，我们在哺乳动物细胞中表达了正常和突变的matrlin-3。野生型(Wt)matrlin-3能有效地分泌到条件培养液中，而突变的matrlin-3则保留并积累在细胞内。此外，当单独检查突变的A-结构域时，它们主要以未折叠的构象存在。免疫共沉淀实验表明，突变的A结构域与ERp72特异相关，ERp72是一种伴侣蛋白，参与介导二硫键的形成。对1例MATN3突变的MED患者的软骨进行光镜检查，发现软骨细胞内有细胞内物质存在，而整个基质看起来正常。在电子显微镜下，光镜下观察到的包涵体似乎是扩张的粗面内质网池，免疫组织化学分析证实残留的蛋白是matrlin-3。综上所述，本文提供的数据表明，MATN3突变引起的MED是突变蛋白在细胞内滞留的结果。Hum Mutat 26(6)，557-565,2005。(C)2005年Wiley-Liss，Inc.
Multiple epiphyseal dysplasia (MED) is a relatively common skeletal dysplasia, that can present in childhood with a variable phenotype of short stature and pain and stiffness in the large joints, and often progresses to early-onset osteoarthritis in adulthood. Mutations in the matrilin-3 gene (MATN3) have recently been shown to underlie some forms of autosomal dominant MED. To date all MED mutations in matrilin-3 cluster in the single A-domain, suggesting that they may disrupt the structure and/or function of this important domain. To determine the effects of MATN3 mutations on the structure and function of matrilin-3 we expressed both normal and mutant matrilin-3 in mammalian cells. Wild,type (wt) matrilin-3 was efficiently secreted into conditioned medium, whereas mutant matrilin-3 was retained and accumulated within the cell. Furthermore, when the mutant A-domains were examined individually, they existed primarily in an unfolded conformation. Co-immunoprecipitation experiments demonstrated that the mutant A,domains were specifically associated with ERp72, a chaperone protein known to be involved in mediating disulfide bond formation. Light microscopy of cartilage from an MED patient with a MATN3 mutation showed the presence of intracellular material within the chondrocytes, whilst the overall matrix appeared normal. On electron micrographs, the inclusions noted at the light microscopy level appeared to be dilated cisternae of rough endoplasmic reticulum and immunohistochemical analysis confirmed that the retained protein was matrilin-3. In summary, the data presented in this paper suggest that MED caused by MATN3 mutations is the result of an intracellular retention of the mutant protein. Hum Mutat 26(6), 557-565, 2005. (c) 2005 Wiley-Liss, Inc.