Immune or Genetic-Mediated Disruption of CASPR2 Causes Pain Hypersensitivity Due to Enhanced Primary Afferent Excitability

J D K Dawes ,Andreas C Themistocleous,Hanns Ulrich Zeilhofer,Kim I Chisholm,Liam Carroll,Ilaria Cervellini,Angela Vincent,Philippa Pettingill,Jorge Galino,Bethan Lang,Teodora Trendafilova,Damini Tewari,Greg A Weir,Maria Pia Giannoccaro,David A Menassa,Johannes Kühnemund,Stephen B Mcmahon,Andrew J Todd,Camilla Buckley,Anthony H Dickenson,Elior Peles,Noboru Iwagaki,Hendrik Wildner,Jan Walcher,Steven J West,Leslie Jacobson,Akila Shakir,Hannah Kuehn,Gary R Lewin,Ryan Patel,Steven J Middleton,Karolina Werynska,Estér Coutinho ,Maria Isabel Leite ,Alex Clark ,Liam J Peck ,María Gutièrrez‐Mecinas ,Maria Domenica Sanna ,J M Sheridan ,David L.h Bennett

doi:10.1016/j.neuron.2018.01.033

Abstract

SummaryHuman autoantibodies to contactin-associated protein-like 2 (CASPR2) are often associated with neuropathic pain, and CASPR2 mutations have been linked to autism spectrum disorders, in which sensory dysfunction is increasingly recognized. Human CASPR2 autoantibodies, when injected into mice, were peripherally restricted and resulted in mechanical pain-related hypersensitivity in the absence of neural injury. We therefore investigated the mechanism by which CASPR2 modulates nociceptive function. Mice lacking CASPR2 (Cntnap2−/−) demonstrated enhanced pain-related hypersensitivity to noxious mechanical stimuli, heat, and algogens. Both primary afferent excitability and subsequent nociceptive transmission within the dorsal horn were increased in Cntnap2−/− mice. Either immune or genetic-mediated ablation of CASPR2 enhanced the excitability of DRG neurons in a cell-autonomous fashion through regulation of Kv1 channel expression at the soma membrane. This is the first example of passive transfer of an autoimmune peripheral neuropathic pain disorder and demonstrates that CASPR2 has a key role in regulating cell-intrinsic dorsal root ganglion (DRG) neuron excitability.

Highlights

Human autoantibodies to contactin-associated protein-like 2 (CASPR2) are often associated with neuropathic pain, and CASPR2 mutations have been linked to autism spectrum disorders, in which sensory dysfunction is increasingly recognized
Either immune or geneticmediated ablation of CASPR2 enhanced the excitability of dorsal root ganglion (DRG) neurons in a cell-autonomous fashion through regulation of Kv1 channel expression at the soma membrane
This is the first example of passive transfer of an autoimmune peripheral neuropathic pain disorder and demonstrates that CASPR2 has a key role in regulating cell-intrinsic dorsal root ganglion (DRG) neuron excitability

Summary

Methods

IgG purification The IgG fraction was purified from the plasma of both CASPR2-Ab patients and the healthy control using protein G Sepharose beads (Sigma). The plasma was diluted 1:4 with Hartmann’s solution and passed through a column containing the Sepharose beads at a flow rate of $0.5ml/minute. Once the diluted plasma had passed through the column, additional Hartmann’s solution was used to wash the beads to ensure no non-specific proteins were present. Coomassie Plus assay kit (Pierce) was used to determine the protein content of the eluted fractions. Fractions with high protein content were dialysed against Hartmann’s solution, concentrated using polyethylene glycol and filter sterilized. For Patient 1 the purified IgG was concentrated to 15mg/ml, for Patient 2 to 11mg/ml and for healthy control to 15mg/ml and 12.5mg/ml, respectively

Results

Discussion

Conclusion