GRM1 and neuromyelitis optica: In fact, most neurological autoantibodies of proven pathogenic impact, such as antibodies to AQP4 in neuromyelitis optica [35–38], acetylcholine receptor in myasthenia gravis, VGCC in Lambert-Eaton syndrome [39] and mGluR1 in paraneoplastic cerebellar degeneration [40], target cell-surface-expressed proteins.