Secreted soluble α2δ-2, α2δ-3 or α2δ-4 calcium channel subunit polypeptides and screening assays using same

A purified or isolated nucleic acid encoding a secreted soluble calcium channel subunit polypeptide that binds gabapentin wherein the sequence of said nucleic acid sequence encodes:

• a polypeptide consisting of from amino-acid 1 to between amino-acids 1047 and 1062 of SEQ ID NO:20, or
• from amino-acid 1 to between amino-acids 1004 and 1019 of SEQ ID NO:22.

A purified or isolated nucleotide sequence encoding a secreted soluble calcium channel subunit polypeptide wherein said sequence consists of the sequence of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:13, SEQ ID NO:14, or SEQ ID NO:15.

A purified or isolated nucleic acid consisting of a nucleic acid that encodes a polypeptide tag fused to a calcium channel subunit polypeptide consisting of:

• from amino-acid 1 to between amino-acids 1027 and 1062 of SEQ ID NO:20, or
• from amino-acid 1 to between amino-acids 984 and 1019 of SEQ ID NO:22.

A purified or isolated nucleic acid consisting of a nucleic acid that encodes a polypeptide tag fused to a calcium channel subunit polypeptide consisting of from amino-acid 1 to between amino-acids 1047 and 1062 of SEQ ID NO:20, or

• from amino-acid 1 to between amino-acids 1004 and 1019 of SEQ ID NO:22.

A purified or isolated nucleotide sequence consisting of a nucleic acid that encodes a polypeptide tag fused to a nucleic acid encoding a calcium channel subunit polypeptide selected from the group consisting of the nucleic acid sequences of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:13, SEQ ID NO:14, and SEQ ID NO:15.