Department of Pathology, The University of Alabama at Birmingham, Birmingham, AL, USA.
Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA.
FASEB J. 2020 Dec;34(12):15687-15700. doi: 10.1096/fj.202000341R. Epub 2020 Oct 13.
Extracellular trafficking of tumor necrosis factor receptor superfamily (TNFRSF) is tightly regulated, disruption of which triggers various autoinflammatory disorders, including TNF receptor-associated periodic syndrome (TRAPS). Here, we provide thus far unraveled molecular basis of noncysteine mutations in TNFR1 ectodomain where loss of an aromatic moiety in cysteine-rich domain (CRD) 2 results in TRAPS disease-associated phenotype. Our study characterized that a missense mutation on phenylalanine residue located in CRD2 (TNFR1 ) causes a delay in TNFR1 transport to cell membrane, leading to sustained receptor responsiveness and downstream NF-κB activation, characteristic of clinical manifestation of a prolonged fever. By creating and characterizing identical mutations on structurally conserved ectodomains of osteoprotegerin (OPG) and decoy receptor 3, other two secreted forms of TNFRSF, we further identified that a conserved aromatic residue at the A1 submodule of CRD2 (A1CRD2) confers structural integrity of ectodomain where aromatic sidechain deletion increases thermal instability, interfering with efficient posttranslational modification and subsequent receptor secretion. Interestingly, our functional analyses indicated that this particular noncysteine mutation is not associated with either protein misfolding or loss of function. Finally, by using a synthetic agonist, we demonstrated gain-of-function of the trafficking defect, suggesting the possibility of rescuing affected pathology in related disorders. Given the structural and topological similarities present in the ectodomains of TNFRSF members, our findings provide mechanistic insights of defects in subcellular trafficking of TNF receptors, reported in various TNFRSF-associated diseases.
肿瘤坏死因子受体超家族（TNFRSF）的细胞外运输受到严格调控，其运输过程的破坏会引发各种自身炎症性疾病，包括肿瘤坏死因子受体相关周期性综合征（TRAPS）。在这里，我们提供了迄今为止已阐明的 TNFRSF 细胞外结构域中非半胱氨酸突变的分子基础，其中富含半胱氨酸结构域（CRD）2 中芳香族部分的缺失导致 TRAPS 疾病相关表型。我们的研究表明，位于 CRD2 上的苯丙氨酸残基上的错义突变（TNFR1）导致 TNFR1 向细胞膜的转运延迟，导致受体持续响应和下游 NF-κB 激活，这是发热时间延长的临床表现特征。通过在骨保护素（OPG）和诱饵受体 3 的结构保守细胞外结构域上创建和表征相同的突变，这两种其他分泌形式的 TNFRSF，我们进一步确定 CRD2 的 A1 亚结构域（A1CRD2）上的保守芳香族残基赋予了细胞外结构域的结构完整性，其中芳香族侧链的缺失增加了热不稳定性，干扰了有效的翻译后修饰和随后的受体分泌。有趣的是，我们的功能分析表明，这种特殊的非半胱氨酸突变与蛋白质错误折叠或功能丧失无关。最后，通过使用合成激动剂，我们证明了运输缺陷的功能获得，这表明在相关疾病中有可能挽救受影响的病理。鉴于 TNFRSF 成员的细胞外结构域存在结构和拓扑相似性，我们的发现为各种 TNFRSF 相关疾病中 TNF 受体亚细胞运输缺陷提供了机制见解。
