AQP4 and neuromyelitis optica: Most neurological autoantibodies of proven pathogenic impact, such as antibodies to AQP4 in neuromyelitis optica [34-36], acetylcholine receptor in myasthenia gravis, VGCC in Lambert Eaton syndrome[37], and mGluR1 in paraneoplastic cerebellar degeneration[10] in fact target transmembrane proteins.