Variant ActRIIB proteins and uses thereof
In certain aspects, the present invention provides compositions and methods for modulating (promoting or inhibiting) growth of red blood cells or a tissue, such as bone, cartilage, muscle, fat, and/or neuronal tissue. The present invention also provides methods of screening compounds that modulate activity of an ActRIIB protein and/or an ActRIIB ligand. The compositions and methods provided herein are useful in treating diseases associated with abnormal activity of an ActRIIB protein and/or an ActRIIB ligand.
1. An isolated ActRIIB polypeptide comprising:
(a) an amino acid sequence that is at least 90% identical to an amino acid sequence that begins at any one of amino acids 20 to 29 of SEQ ID NO: 2 and
(b) ends at any one of amino acids 109 to 134 of SEQ ID NO: 2; and wherein the polypeptide comprises a lysine at the position corresponding to position 82 of SEQ ID NO: 2, wherein the ActRIIB polypeptide maintains inhibition of activin A and GDF11, and demonstrates less potent inhibition of BMP9, compared to a wild-type ActRIIB polypeptide.
2. The polypeptide of claim 1 , wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 29-109 of SEQ ID NO: 2.
3. The polypeptide of claim 1 , wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 20-134 of SEQ ID NO: 2.
4. The polypeptide of claim 1 , wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to amino acids 25-131 of SEQ ID NO: 2.
5. The polypeptide of claim 4 , wherein the ActRIIB polypeptide comprises an amino acid sequence that is at least 90% identical to SEQ ID NO: 53.
6. The polypeptide of claim 1 , wherein the ActRIIB polypeptide is a fusion protein further comprising an Fc polypeptide domain.
7. The polypeptide of claim 6 , wherein the fusion protein further comprises a linker domain positioned between the ActRIIB polypeptide and the Fc polypeptide domain.
8. The polypeptide of claim 7 , wherein the linker domain is selected from the group consisting of TGGG (SEQ ID NO: 265), TGGGG (SEQ ID NO: 263), SGGGG (SEQ ID NO: 264), GGGGS (SEQ ID NO: 267), GGG (SEQ ID NO: 261), GGGG (SEQ ID NO: 262), and SGGG (SEQ ID NO: 266).
9. The polypeptide of claim 7 , wherein the linker domain comprises GGG.
10. The polypeptide of claim 6 , wherein the fusion protein comprises an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 5.
11. The polypeptide of claim 6 , wherein the fusion protein comprises an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 6.
12. The polypeptide of claim 6 , wherein the fusion protein comprises an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 12.
13. The polypeptide of claim 6 , wherein the fusion protein comprises an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 40.
14. The polypeptide of claim 6 , wherein the fusion protein comprises an amino acid sequence that is at least 90% identical to the amino acid sequence of SEQ ID NO: 42.
15. The polypeptide of claim 6 , wherein the fusion protein is encoded by a nucleic acid sequence that is at least 90% identical to the nucleic acid sequence of SEQ ID NO: 41.
16. The polypeptide of claim 1 , wherein the ActRIIB polypeptide is a homodimer protein.
17. The polypeptide of claim 1 , wherein the ActRIIB polypeptide is a heterodimer protein.
18. The polypeptide of claim 17 , wherein the heterodimer comprises a second ActRIIB polypeptide, wherein the first ActRIIB polypeptide comprises a different amino acid sequence compared to the second ActRIIB polypeptide.
19. The polypeptide of claim 18 , wherein the second ActRIIB polypeptide is a wild-type ActRIIB extracellular domain polypeptide.
20. The polypeptide of claim 1 , wherein the ActRIIB polypeptide is glycosylated and has a glycosylation pattern obtainable from expression of the polypeptide in a CHO cell.
21. A pharmaceutical composition comprising the ActRIIB polypeptide of claim 1 , and a pharmaceutically acceptable carrier.