Habib Margarita, Wiessler Anna-Lena, Fischer Patrik, Niesner Michele, Selcho Mareike, Abrante Ligia, Werner Christian, Sodmann Annemarie, Koch Maximilian, Zare Abdolhossein, Prüss Harald, Dargvainiene Justina, Lewerenz Jan, Handreka Robert, Körtvelyessy Peter, Reinhold Dirk, Thaler Franziska S, Pitarokoili Kalliopi, Kittel Robert J, Briese Michael, Sendtner Michael, Rittner Heike, Leypoldt Frank, Sommer Claudia, Blum Robert, Doppler Kathrin, Villmann Carmen
Institute for Clinical Neurobiology, University Hospital Wuerzburg, Germany.
Department of Neurology, University Hospital Wuerzburg, Germany.
Neurol Neuroimmunol Neuroinflamm. 2025 Jul;12(4):e200423. doi: 10.1212/NXI.0000000000200423. Epub 2025 Jun 25.
Patients with autoantibodies (aAbs) against the contactin-associated protein-like 2 (CASPR2) suffer from a variety of clinical syndromes including neuropathic pain. CASPR2 is an adhesion protein of the neurexin family and part of the voltage-gated potassium channel complex (VGKC complex) in dorsal root ganglia (DRG) neurons. The pathologic mechanisms following the binding of CASPR2 aAbs and their association with pain are only partially understood. CASPR2 aAbs are mainly of the IgG4 subclass; however, previous studies have neglected subclass-dependent effects.
We investigated 49 subclassified patient serum samples positive for CASPR2 aAbs combining superresolution lattice structural illumination microscopy (SIM) and functional readouts by calcium imaging and electrophysiologic recordings on cultured DRG neurons. CASPR2-positive patient sera subclassified in IgG4 together with at least 1 other IgG subclass (IgGX) and patients with only IgG4 were further subdivided into the pain and no pain groups.
A decrease of CASPR2 expression along the axons after exposure to CASPR2 aAbs was observed for all patient groups except the group without pain and IgG4. Moreover, binding of CASPR2 aAbs from patients with pain increased the distance between CASPR2 and associated potassium channels along DRG axons determined by SIM microscopy. CASPR2 aAbs of patients with pain significantly increased overall neuronal excitability of cultured DRG neurons as measured by calcium imaging. Patch-clamp recordings revealed significantly decreased current amplitudes of voltage-gated potassium (Kv) channels after incubation with all 4 CASPR2 aAb subclassifications with the most prominent effect of serum samples harboring IgG4 aAbs only. Replacement of patient aAbs by healthy control serum rescued Kv channel function to normal levels suggesting that the affected potassium channel function is due to structural blockage and disrupted interactions within the VGKC complex. The last might also be rescued on novel protein synthesis and membrane trafficking of CASPR2.
IgG4 aAbs seem to be the major modifier of potassium channel function. The DRG hyperexcitability is primarily due to impaired Kv channel conductance as a consequence of CASPR2 aAb binding. However, additional unidentified signal pathways contribute to this process in patients with neuropathic pain.
抗接触蛋白相关蛋白样2（CASPR2）自身抗体（aAbs）的患者患有多种临床综合征，包括神经性疼痛。CASPR2是神经连接蛋白家族的一种粘附蛋白，是背根神经节（DRG）神经元中电压门控钾通道复合物（VGKC复合物）的一部分。CASPR2自身抗体结合后的病理机制及其与疼痛的关联仅得到部分理解。CASPR2自身抗体主要为IgG4亚类；然而，以往研究忽略了亚类依赖性效应。
我们通过超分辨率晶格结构照明显微镜（SIM）以及对培养的DRG神经元进行钙成像和电生理记录的功能读数，研究了49份CASPR2自身抗体阳性的亚分类患者血清样本。IgG4与至少1种其他IgG亚类（IgGX）一起亚分类的CASPR2阳性患者血清以及仅患有IgG4的患者被进一步细分为疼痛组和无疼痛组。
除无疼痛且为IgG4的组外，所有患者组在暴露于CASPR2自身抗体后均观察到沿轴突的CASPR2表达减少。此外，通过SIM显微镜测定，疼痛患者的CASPR2自身抗体结合增加了沿DRG轴突的CASPR2与相关钾通道之间的距离。通过钙成像测量，疼痛患者的CASPR2自身抗体显著增加了培养的DRG神经元的整体神经元兴奋性。膜片钳记录显示，与所有4种CASPR2自身抗体亚分类孵育后，电压门控钾（Kv）通道的电流幅度显著降低，其中仅含有IgG4自身抗体的血清样本影响最为显著。用健康对照血清替代患者自身抗体可将Kv通道功能恢复至正常水平，表明受影响的钾通道功能是由于结构阻塞和VGKC复合物内相互作用中断所致。后者也可能通过CASPR2的新蛋白质合成和膜转运得到挽救。
IgG4自身抗体似乎是钾通道功能的主要调节因子。DRG兴奋性过高主要是由于CASPR2自身抗体结合导致Kv通道电导受损。然而，在神经性疼痛患者中，其他未明确的信号通路也参与了这一过程。
