Peptides having reduced toxicity that stimulate cholesterol efflux
The present invention provides a family of non-naturally occurring polypeptides having cholesterol efflux activity that parallels that of full-length apolipoproteins (e.g., Apo AI and Apo E), and having high selectivity for ABCA1 that parallels that of full-length apolipoproteins. Further, the peptides of the invention have little or no toxicity when administered at therapeutic and higher doses. The invention also provides compositions comprising such polypeptides, methods of identifying, screening and synthesizing such polypeptides, and methods of treating, preventing or diagnosing diseases and disorders associated with dyslipidemia, hypercholesterolemia, or inflammation; or diseases involving abnormal glucose metabolism, e.g., diabetes, metabolic syndrome; or Alzheimer's Disease or frontotemporal dementia.
1. An isolated polypeptide having cholesterol efflux activity, the polypeptide comprising an amino acid sequence that is an amphipathic α-helix that has a non-polar surface and a polar surface, wherein the polar surface comprises charged and uncharged amino acid residues at the lipid-water interface, wherein the amino acid sequence:
has at least 60% identity to SEQ ID NO:1; and
has a citrulline, or an uncharged analog of citrulline that maintains a salt-bridge configuration in the α-helix, at at least one of the three positions 3, 14, and 23 as determined with reference to SEQ ID NO:1;
comprises a hydrophobic amino acid at positions 2, 6, 9, 10, 13, 16, 17, 20, and 24 as determined with reference to SEQ ID NO:1; and
comprises an acidic amino acid residue at positions 1, 7, 8, 15, 18, and 19 as determined with reference to SEQ ID NO:1.
2. The isolated polypeptide of claim 1 , wherein the amino acid sequence comprises an uncharged amino acid at a second of the three positions 3, 14, and 23.
3. The isolated polypeptide of claim 1 , wherein the amino acid sequence comprises an uncharged amino acid at the second and third of the three positions 3, 14, and 23.
4. The isolated polypeptide of claim 1 , wherein the α-helix amino acid sequence is 24 amino acid in length and further comprises a position 25 and 26, wherein position 25 is K or N and position 26 is S or Y.
5. The isolated polypeptide of claim 1 , wherein the amino acid sequence has Q, N, L, V, I, or A at at least one position 3, 14, or 23.
6. The isolated polypeptide of claim 5 , wherein the amino acid sequence has Q or N at at least one position 3, 14, or 23.
7. The isolated polypeptide of claim 1 , wherein the amino acid sequence comprises an amino acid residue at two of positions 3, 14, and 23 that are independently selected from Q, N, L, V, I, or A.
8. The isolated polypeptide of claim 1 , wherein the amino acid sequence comprises R or K at at least one of positions 3, 14, and 23.
9. The isolated polypeptide of claim 1 , wherein four, five, six, seven, or all eight of residues at positions 2, 6, 10, 13, 16, 17, 20, and 24 are aliphatic amino acids.
10. The isolated polypeptide of claim 9 , wherein the aliphatic amino acid is selected from the group consisting of L, V, A, and I.
11. The isolated polypeptide of claim 9 , wherein the residue at position 10, 13, 16, and 20 is selected from the group consisting of L, I, and V.
12. The isolated polypeptide of claim 1 , wherein the polypeptide further comprises a protecting group.
13. The isolated polypeptide of claim 1 , wherein the peptide comprises enantiomeric “D” amino acids.
14. A composition comprising a polypeptide of claim 1 and a pharmaceutically acceptable carrier.
15. The isolated polypeptide of claim 12 , wherein the protecting group is selected from the group consisting of acetyl (Ac), amide, 3 to 20 carbon alkyl groups, Fmoc, t-butoxycarbonyl (Tboc), 9-fluoreneacetyl group, 1-fluorenecarboxylic group, 9-fluorenecarboxylic group, 9-fluorenone-1-carboxylic group, benzyloxycarbonyl, xanthyl (Xan), trityl (Trt), 4-methyltrityl (Mtt), 4-methoxytrityl (Mmt), 4-methoxy-2,3,6-trimethyl-benzenesulphonyl (Mtr), mesitylene-2-sulphonyl (Mts), 4,4-dimethoxybenzhydryl (Mbh), tosyl (Tos), 2,2,5,7,8-pentamethyl chroman-6-sulphonyl (Pmc), 4-methylbenzyl (MeBzl), 4-methoxybenzyl (MeOBzl), benzyloxy (BzlO), benzyl (Bzl), benzoyl (Bz), 3-nitro-2-pyridinesulphenyl (Npys), 1-(4,4-dimethyl-2,6-dioxocyclohexylidene)ethyl (Dde), 2,6-dichlorobenzyl (2,6-DiCl-Bzl), 2-chlorobenzyloxycarbonyl (2-Cl-Z), 2-bromobenzyloxycarbonyl (2-Br-Z), benzyloxymethyl (Bom), cyclohexyloxy (cHxO), t-butoxymethyl (Bum), t-butoxy (tBuO), t-butyl (tBu), and trifluoroacetyl (TFA).
16. The isolated polypeptide of claim 12 , wherein the protecting group is coupled to the amino or carboxy terminus.
17. The isolated polypeptide of claim 12 , wherein the polypeptide comprises a first protecting group coupled to the amino terminus and a second protecting group coupled to the carboxyl terminus.
18. The isolated polypeptide of claim 17 , wherein the first protecting group is a protecting group selected from the group consisting of acetyl, propionyl, and a 3 to 20 carbon alkyl.
19. The isolated polypeptide of claim 18 , wherein the first protecting group is an acetyl.
20. The isolated polypeptide of claim 17 , wherein the second protecting group is an amide.
21. The isolated polypeptide of claim 1 , wherein the peptide comprises enantiomeric amino acids that are a mixture of “L” amino acids and “D” amino acids.
22. A retro-inverso or a retro-enantio analog of a polypeptide having cholesterol efflux activity, wherein the polypeptide comprises an amino acid sequence that is an amphipathic α-helix that has a non-polar surface and a polar surface, wherein the polar surface comprises charged and uncharged amino acid residues at the lipid-water interface, wherein the amino acid sequence:
has at least 60% identity to SEQ ID NO:1, and
has a citrulline, or an uncharged analog of citrulline that maintains a salt-bridge configuration in the α-helix, at at least one of the three positions 3, 14, and 23 as determined with reference to SEQ ID NO:1;
comprises a hydrophobic amino acid at positions 2, 6, 9, 10, 13, 16, 17, 20, and 24 as determined with reference to SEQ ID NO:1, and
comprises an acidic amino acid residue at positions 1, 7, 8, 15, 18, and 19 as determined with reference to SEQ ID NO:1.
23. A composition comprising a polypeptide of claim 1 complexed with a lipid.