GRM1 and aceruloplasminemia: On the other hand, antibodies directed against the neural cell surface or synaptic proteins (such as P/Q-type voltage-gated calcium channels (VGCCs) and metabotropic glutamate receptor 1 (mGluR1) antibodies), are thought to have a direct pathogenic role as they link to surface receptors, causing blockage and internalization, which ultimately results in cerebellar ataxia [38].