The present invention provides nucleic acid and polypeptide sequences describing a novel isoform of the .alpha.2.delta. subunit of a voltage gated calcium channel, herein named as .alpha.2.delta.-4. The isolated nucleic acid or polypeptide molecule of the invention can be used in diagnosing and treating a disease or disorder associated with a defective .alpha.2.delta.-4 subunit, such as seizure-related syndromes, anxiety, multiple sclerosis, and the like.