Discovered is a novel protein and variants thereof whose activity at the NMDA receptor causes an increased efflux of calcium ions through the channel of said receptor. This activity is downregulated by the NR3A subunit of NMDA. Also discovered are the nucleic acid sequences encoding said novel protein and variants thereof. The discovery is useful for the diagnosing of NMDA receptor dysregulation and the treatment of NMDA receptor dysregulation related disorders. In addition, the discovery is useful for the further discovery of modulators affecting the activity of the novel protein and variants thereof at the NMDA receptor.