Aberrant binding of mutant HSP47 affects posttranslational modification of type I collagen and leads to osteogenesis imperfecta.
Aberrant binding of mutant HSP47 affects posttranslational modification of type I collagen and leads to osteogenesis imperfecta.
复制标题
突变型HSP 47的异常结合影响I型胶原蛋白的翻译后修饰并导致骨生成抑制。
DOI：
10.1371/journal.pgen.1009339
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发表时间：
2021-03
期刊：
影响因子：
4.5
通讯作者：
Malfait F
中科院分区：
文献类型：
--
作者：
Syx D;Ishikawa Y;Gebauer J;Boudko SP;Guillemyn B;Van Damme T;D'hondt S;Symoens S;Nampoothiri S;Gould DB;Baumann U;Bächinger HP;Malfait F
热休克蛋白47（HSP 47）是由SERPINH 1基因编码的一种分子伴侣，对胶原蛋白的正确折叠至关重要。我们报告了一个纯合子p。（R222 S）取代HSP 47在儿童严重骨生成障碍导致早期死亡。p.R222是位于HSP 47的胶原相互作用表面内的高度保守的残基。结合测定显示HSP 47-R222 S对I型胶原的亲和力显著降低。这种改变的相互作用导致由真皮成纤维细胞产生的I型前胶原的翻译后过度修饰，如质谱所示，赖氨酸和脯氨酸残基的糖基化和/或羟基化增加。由于我们还观察到正常的细胞内折叠和分泌速率的I型前胶原，这种过度修饰不能解释为长期暴露的前胶原分子的修饰羟基和糖基转移酶，如常见的其他类型的OI。我们在Western印迹和RT-qPCR上发现了参与前胶原修饰和折叠的几种分子伴侣和酶的显著上调。此外，我们发现，在明胶琼脂糖凝胶下拉试验中，HSP 47-R222 S与未折叠的I型胶原蛋白链的结合不平衡导致其他分子伴侣和修饰酶的结合增加。该分子系综与I型前胶原的表达和结合的升高提示了HSP 47-R222 S的异常结合的补偿机制，最终导致I型前胶原链的过度修饰。总之，这些结果说明了HSP 47的重要性，适当的翻译后修饰，并提供深入了解的分子病理机制的p。HSP 47的R222 S改变导致严重的OI表型。热休克蛋白47（HSP 47）是胶原蛋白正确折叠所必需的。我们报告了一个纯合子p。（R222 S）取代HSP 47在儿童严重成骨发育不良。高度保守的p.R222残基位于胶原蛋白相互作用表面内，并且HSP 47-R222 S显示出对I型胶原蛋白的显著降低的亲和力。这种改变的相互作用导致I型前胶原的翻译后过度修饰。与其他类型的OI相反，这种过度修饰不是由前胶原长时间暴露于修饰酶引起的，因为I型前胶原的细胞内折叠速率似乎是正常的。我们发现几种分子伴侣和胶原蛋白修饰酶的显著上调，以及这些分子中的几种在异常HSP 47-R222 S结合后与未折叠的I型胶原蛋白链的结合增加。这表明了一种补偿机制异常HSP 47-R222 S结合，最终导致过度修饰的I型前胶原链，并强调了HSP 47的重要性，适当的翻译后修饰。
Heat shock protein 47 (HSP47), encoded by the SERPINH1 gene, is a molecular chaperone essential for correct folding of collagens. We report a homozygous p.(R222S) substitution in HSP47 in a child with severe osteogenesis imperfecta leading to early demise. p.R222 is a highly conserved residue located within the collagen interacting surface of HSP47. Binding assays show a significantly reduced affinity of HSP47-R222S for type I collagen. This altered interaction leads to posttranslational overmodification of type I procollagen produced by dermal fibroblasts, with increased glycosylation and/or hydroxylation of lysine and proline residues as shown by mass spectrometry. Since we also observed a normal intracellular folding and secretion rate of type I procollagen, this overmodification cannot be explained by prolonged exposure of the procollagen molecules to the modifying hydroxyl- and glycosyltransferases, as is commonly observed in other types of OI. We found significant upregulation of several molecular chaperones and enzymes involved in procollagen modification and folding on Western blot and RT-qPCR. In addition, we showed that an imbalance in binding of HSP47-R222S to unfolded type I collagen chains in a gelatin sepharose pulldown assay results in increased binding of other chaperones and modifying enzymes. The elevated expression and binding of this molecular ensemble to type I procollagen suggests a compensatory mechanism for the aberrant binding of HSP47-R222S, eventually leading to overmodification of type I procollagen chains. Together, these results illustrate the importance of HSP47 for proper posttranslational modification and provide insights into the molecular pathomechanisms of the p.(R222S) alteration in HSP47, which leads to a severe OI phenotype. Heat shock protein 47 (HSP47) is essential for correct collagen folding. We report a homozygous p.(R222S) substitution in HSP47 in a child with severe osteogenesis imperfecta. The highly conserved p.R222 residue is located within the collagen interacting surface and HSP47-R222S shows a significantly reduced affinity for type I collagen. This altered interaction leads to posttranslational overmodification of type I procollagen. In contrast to other types of OI, this overmodification is not caused by prolonged exposure of procollagen to modifying enzymes, since the intracellular folding rate of type I procollagen appears to be normal. We show significant upregulation of several molecular chaperones and collagen-modifying enzymes and increased binding of several of these molecules to unfolded type I collagen chains upon abnormal HSP47-R222S binding. This suggests a compensatory mechanism for aberrant HSP47-R222S binding, eventually leading to overmodification of type I procollagen chains, and underscores the importance of HSP47 for proper posttranslational modification.