Liu Xin, Liu Kaiqing, Nie Danyao, Zhang Jing, Zhang Liyun, Liu Xinhua, Wang Jiantao
Shenzhen Eye Hospital, Shenzhen Key Laboratory of Ophthalmology, Affiliated Shenzhen Eye Hospital of Jinan University, Shenzhen, China.
Guangdong Key Laboratory of Systems Biology and Synthetic Biology for Urogenital Tumors, Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen, China.
Front Genet. 2022 Aug 11;13:928683. doi: 10.3389/fgene.2022.928683. eCollection 2022.
Marfan syndrome, an autosomal dominant disorder of connective tissue, is primarily caused by mutations in the fibrillin-1 (FBN1) gene, which encodes the protein fibrillin-1. The protein is composed of epidermal growth factor-like (EGF-like) domains, transforming growth factor beta-binding protein-like (TB) domains, and hybrid (Hyb) domains and is an important component of elastin-related microfibrils in elastic fiber tissue. In this study, we report a cysteine to tyrosine substitution in two different domains of fibrillin-1, both of which cause Marfan syndrome with ocular abnormalities, in two families. Using protease degradation and liquid chromatography-tandem mass spectrometry analyses, we explored the different effects of substitution of cysteine by tyrosine in an EGF-like and a calcium-binding (cb) EGF-like domain on protein stability. The results showed that cysteine mutations in the EGF domain are more likely to result in altered proteolytic sensitivity and thermostability than those in the cbEGF domain. Furthermore, cysteine mutations can lead to new enzymatic sites exposure or hidden canonical cleavage sites. These results indicate the differential clinical phenotypes and molecular pathogenesis of Marfan syndrome caused by cysteine mutations in different fibrillin-1 domains. These results strongly suggest that failure to form disulfide bonds and abnormal proteolysis of fibrillin-1 caused by cysteine mutations may be an important factor underlying the pathogenesis of diseases caused by fibrillin-1 mutations, such as Marfan syndrome.
马凡综合征是一种常染色体显性结缔组织疾病，主要由原纤维蛋白-1（FBN1）基因突变引起，该基因编码原纤维蛋白-1。该蛋白由表皮生长因子样（EGF样）结构域、转化生长因子β结合蛋白样（TB）结构域和杂合（Hyb）结构域组成，是弹性纤维组织中弹性蛋白相关微原纤维的重要组成部分。在本研究中，我们报告了在两个家族中，原纤维蛋白-1的两个不同结构域发生了半胱氨酸到酪氨酸的替换，这两种替换均导致伴有眼部异常的马凡综合征。我们使用蛋白酶降解和液相色谱-串联质谱分析，探究了在一个EGF样结构域和一个钙结合（cb）EGF样结构域中半胱氨酸被酪氨酸替换对蛋白质稳定性的不同影响。结果表明，与cbEGF结构域中的半胱氨酸突变相比，EGF结构域中的半胱氨酸突变更有可能导致蛋白水解敏感性和热稳定性的改变。此外，半胱氨酸突变可导致新的酶切位点暴露或隐藏的典型切割位点。这些结果表明了不同原纤维蛋白-1结构域中的半胱氨酸突变所导致的马凡综合征的不同临床表型和分子发病机制。这些结果有力地表明，半胱氨酸突变导致的原纤维蛋白-1无法形成二硫键和异常蛋白水解可能是由原纤维蛋白-1突变引起的疾病（如马凡综合征）发病机制的一个重要因素。
