Osaki Tsukasa, Souri Masayoshi, Ozawa Tatsuhiko, Muraguchi Atsushi, Ichinose Akitada
Department of Molecular Patho-Biochemistry and Patho-Biology, Yamagata University School of Medicine, Japan.
The Japanese Collaborative Research Group (JCRG) on Autoimmune Acquired Coagulation Factor Deficiencies supported by the Japanese Ministry of Health, Labor and Welfare (MHLW), Yamagata, Japan.
FEBS Lett. 2023 May;597(9):1275-1289. doi: 10.1002/1873-3468.14606. Epub 2023 Mar 22.
Autoimmune coagulation factor XIII (FXIII) deficiency (AiF13D) is a bleeding disorder caused by anti-FXIII autoantibodies. Recently, we generated human monoclonal antibodies (mAbs) from the peripheral blood of an AiF13D patient and classified them into three groups: FXIII-dissociation inhibitor, FXIII-assembly inhibitor, and non-neutralizing/inhibitory mAbs. However, the epitope region and molecular inhibitory mechanism of each mAb remain unknown. Here, we localized the epitope regions of the representative inhibitory mAbs A69K (dissociation inhibitor) and A78L (assembly inhibitor) to the β-barrel-2 domain and boundary of β-barrel-1&2 domains, respectively, of the FXIII-A subunit, by combining a binding assay using its synthesized peptides and a protease-protection assay. Our findings suggest that A69K inhibits the activation-related conformational changes and dissociation of FXIII and that A78L competitively inhibits FXIII-assembly.
自身免疫性凝血因子 XIII（FXIII）缺乏症（AiF13D）是一种由抗 FXIII 自身抗体引起的出血性疾病。最近，我们从一名 AiF13D 患者的外周血中产生了人单克隆抗体（mAb），并将它们分为三组：FXIII 解离抑制剂、FXIII 组装抑制剂和非中和/抑制性 mAb。然而，每种 mAb 的表位区域和分子抑制机制仍然未知。在这里，我们通过结合使用其合成肽的结合试验和蛋白酶保护试验，将代表性抑制性 mAb A69K（解离抑制剂）和 A78L（组装抑制剂）的表位区域分别定位到 FXIII-A 亚基的β桶-2 结构域和β桶-1&2 结构域的边界。我们的研究结果表明，A69K 抑制 FXIII 的激活相关构象变化和解离，而 A78L 竞争性抑制 FXIII 组装。
