Protein that enhances expression of potassium channels on cell surfaces and nucleic acids that encode the same

The present invention provides polynucleotides that encode a protein, designated herein as K+ Channel Associated Protein or "KChAP". It has been determined that expressing polynucleotides that encode KChAP in host cells, along with polynucleotides that encode the Kv.alpha. channel subunit Kv 2.1, the Kv.alpha. channel subunit Kv 2.2, the Kv.alpha. channel subunit Kv 1.3, or the Kv.alpha. channel subunit Kv 4.3, increases the number of Kv2.1, Kv 2.2, Kv1.3 or Kv4.3 channels, respectively, in the plasma membrane of such cells. The present invention also relates to a method of making cells that have increased numbers of Kv channels on the plasma membranes thereof and to a method of using such cells as model systems for studying the effect of pharmacological agents on Kv channels, particularly on Kv2.1, Kv 2.2, Kv 1.3, and Kv 4.3 channels. The present invention also relates to the protein KChAP.

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What is claimed is:

1. An isolated polynucleotide comprising a nucleotide sequence encoding a KChAP protein which binds to Kv.alpha. subunits and increases number of Kv channels in transfectedcell or a nucleotide sequence complementary to a nucleotide sequence encoding said KChAP protein, wherein said KChAP protein comprises an amino acid sequence which is at least 95% identical to SEQ ID NO: 2 or SEQ ID NO: 4.

2. The polynucleotide of claim 1 wherein said sequence encodes a protein selected from the group consisting of a human KChAP protein comprising an amino acid sequence which is at least 95% identical to SEQ ID NO: 4 and a rat KChAP proteincomprising an amino acid sequence which is at-least 95% identical to SEO ID NO:2.

3. An isolated polynucleotide comprising a nucleotide sequence encoding a protein selected from the group consisting of a rat KChAP protein which binds to Kv.alpha. subunits and increases number of Kv channels in transfected cell comprising anamino acid sequence which is at least 95% identical to SEQ ID NO:2, a human KChAP protein which binds to Kv.alpha. subunits and increases number of Kv channels in transfected cell comprising an amino acid sequence which at least 95% identical to SEQ IDNO: 4; and a variant of said rat and said human KChAP proteins, said variant comprising the amino acid sequence of SEQ ID NO: 6.

4. The polynucleotide of claim 1 wherein said nucleotide sequence encodes a KChAP protein comprising an amino acid sequence selected from the group consisting of:

(a) the amino acid sequence of SEQ ID NO: 2;

(b) the amino acid sequence of SEQ ID NO: 4; and

(c) the amino acid sequence of SEQ ID NO: 6.

5. The polynucleotide of claim 3 wherein the nucleotide sequence encodes a rat KChAP protein comprising the amino acid sequence of SEQ ID NO: 2or an allelic variant thereof.

6. The polynucleotide of claim 3 wherein the nucleotide sequence encodes a human KCHAP protein comprising the amino acid sequence of SEQ ID NO: 4, or an allelic variant thereof.

7. The polynucleotide of claim 1 wherein said polynucleotide comprises a nucleotide sequence selected from the group consisting of:

a) a sequence which is at least 95% identical to the nucleotide sequence of SEQ ID NO:1;

b) a sequence complementary to the nucleotide sequence of SEQ ID NO: 1;

c) a sequence which is at least 95% identical to the nucleotide sequence of SEQ ID NO:3; and

d) a sequence complementary to the nucleotide sequence of SEQ ID NO: 3.

8. The polynucleotide of claim 1 wherein said KCHAP protein binds to the N-termini of the Kv.alpha. subunits Kv2.1, Kv2.2, Kv1.3, and Kv4.3 and to the C-terminus of Kv.beta.1.2 and wherein said KChAP protein comprises a Kva.alpha./Kv.beta. binding domain which comprises the amino acid sequence of SEQ ID NO: 10.

9. The polynucleotide of claim 8 wherein said protein further comprises a C terminal domain which comprises the amino acid sequence of SEQ ID NO: 11.

10. A host cell comprising a polynucleotide encoding a KChAP protein, which binds to Kv.alpha. subunits and increases number of Kv channels in transfected cell said KChAP protein comprising an amino acid sequence which is at least 95% identicalto SEO ID NO: 4 or SEO ID. NO:2, and a polynucleotide encoding an exogenous Kv.alpha. subunit.

11. The host cell of claim 10 wherein the Kv.alpha. subunit is selected from the group consisting of Kv2.1, Kv2.2, Kv1.3 and Kv4.3.

12. A host cell comprising an expression vector comprising a nucleic acid sequence which encodes a rat KChAP protein which binds to Kv.alpha. subunits and increases number of Kv channels in transfected cell, wherein said protein comprises anamino acid sequence which is at least 95% identical to the amino acid sequence of SEQ ID NO:2 or the amino acid sequence of SEQ ID NO:4.

13. The polynucleotide of claim 7 wherein the polynucleotide comprises the sequence of SEQ ID NO: 1 or the sequence of SEQ ID NO:3.