Division of Molecular Internal Medicine, Department of Internal Medicine II, University Hospital Würzburg, Röntgenring 11, 97070 Würzburg, Germany.
J Biol Chem. 2013 May 10;288(19):13455-66. doi: 10.1074/jbc.M112.435917. Epub 2013 Mar 26.
Fn14 is a therapeutic target in various diseases.
Anti-Fn14 antibodies activate the alternative NFκB pathway but not other Fn14-related activities induced by soluble or membrane-bound TWEAK. FcγR-bound anti-Fn14 antibodies, however, activate the full spectrum of Fn14-associated activities.
Anti-Fn14 antibodies elicit agonistic activities differing from those of the natural Fn14 ligand TWEAK.
These findings influence the rationale of designing Fn14-targeted therapies. The Fn14-specific monoclonal antibodies PDL192 and P4A8, which are under consideration in clinical trials, showed no agonistic activity with respect to IL8 production and cell death induction. However, oligomerization with protein G or binding to Fcγ receptors converted both anti-Fn14 antibodies into potent agonists. TNF-like weak inducer of apoptosis (TWEAK), the ligand of Fn14, occurs naturally in two forms with partly different signaling capabilities, as a membrane-bound ligand and as a soluble trimeric molecule. Although membrane TWEAK strongly triggers all Fn14-associated pathways, soluble TWEAK predominately triggers the alternative nuclear factor κB (NFκB) pathway and enhances TNF-induced cell death but has only a poor effect on the classical NFκB pathway and chemokine production. Thus, the oligomerized and FcγR-bound anti-Fn14 mAbs mimicked the activity of membrane TWEAK. Notably, both anti-Fn14 antibodies significantly triggered p100 processing, the hallmark of the alternative NFκB pathway, and therefore resembled soluble TWEAK. In contrast to the latter, however, the anti-Fn14s showed no effect on TNF receptor 1-induced cell death and P4A8 even blocked the corresponding TWEAK response. Thus, we showed that Fn14 antibodies display an alternative NFκB pathway-specific agonistic activity but fail to phenocopy other activities of soluble TWEAK, whereas oligomerized or FcγR-bound Fn14 antibodies fully mimic the activity of membrane TWEAK. In view of the trivalent nature of the TWEAK-Fn14 interaction, this suggests that the alternative NFκB pathway is uniquely responsive already to Fn14 dimerization enabling antibodies to elicit an unnatural response pattern distinct from that of the naturally occurring Fn14 ligands.
Fn14 是各种疾病的治疗靶点。
抗 Fn14 抗体激活替代 NFκB 途径，但不激活可溶性或膜结合 TWEAK 诱导的其他 Fn14 相关活性。然而，FcγR 结合的抗 Fn14 抗体激活了与 Fn14 相关的所有活性。
抗 Fn14 抗体引起的激动活性与天然 Fn14 配体 TWEAK 不同。
这些发现影响了设计针对 Fn14 的治疗方法的原理。正在临床试验中考虑的 Fn14 特异性单克隆抗体 PDL192 和 P4A8 对 IL8 产生和细胞死亡诱导没有表现出激动活性。然而，与蛋白 G 寡聚化或与 Fcγ 受体结合将两种抗 Fn14 抗体转化为有效的激动剂。TNF 样凋亡弱诱导剂（TWEAK）是 Fn14 的配体，以两种部分不同信号转导能力的形式自然存在，作为膜结合配体和可溶性三聚体分子。虽然膜 TWEAK 强烈触发所有 Fn14 相关途径，但可溶性 TWEAK 主要触发替代核因子 κB（NFκB）途径并增强 TNF 诱导的细胞死亡，但对经典 NFκB 途径和趋化因子产生仅有较差的影响。因此，寡聚化和 Fcγ 受体结合的抗 Fn14 mAb 模拟了膜 TWEAK 的活性。值得注意的是，两种抗 Fn14 抗体都显著触发了替代 NFκB 途径的标志性 p100 加工，因此类似于可溶性 TWEAK。然而，与后者不同的是，抗 Fn14 对 TNF 受体 1 诱导的细胞死亡没有影响，而 P4A8 甚至阻断了相应的 TWEAK 反应。因此，我们表明 Fn14 抗体显示替代 NFκB 途径特异性激动活性，但不能模拟可溶性 TWEAK 的其他活性，而寡聚化或 Fcγ 受体结合的 Fn14 抗体完全模拟膜 TWEAK 的活性。鉴于 TWEAK-Fn14 相互作用的三价性质，这表明替代 NFκB 途径已经对 Fn14 二聚化有反应性，从而使抗体能够引起与天然存在的 Fn14 配体不同的不自然反应模式。
