Methods of identifying opioid cyclic peptides
Novel cyclic peptides, cyclic peptide conjugates and compositions containing them for treating neurological diseases in a subject include an Odorranalectin (OL) sequence or modified OL sequence as a scaffold and a biologically active peptide or protein and/or therapeutic agent conjugated thereto. Methods of treatment of neurological diseases are based on intranasal delivery of a cyclic peptide or cyclic peptide conjugate as described herein. Combinatorial libraries that include a plurality of cyclic peptides have also been developed and can be used to screen for a ligand(s) for a receptor of interest.
1. A method of identifying opioid cyclic peptides comprising:
i) providing a combinatorial library comprising a plurality of distinct cyclic peptides of the general Formula II:
(SEQ ID NO: 18)
Tyr-Ala-Ser-Pro-Lys-cyclo-[Cys-Phe-Arg-XXXXX-
Leu-Ala-Cys]-Thr,
wherein each X is an amino acid selected from the group consisting of: D-amino acid, L-amino acid, non-natural synthetic amino acid, naturally occurring amino acid, and a mixture thereof;
ii) screening the plurality of cyclic peptides for binding affinity to μ-opioid receptor (MOR), δ-opioid receptor (DOR), and κ-opioid receptor (KOR) in mammalian cells
using a screening assay to identify any cyclic peptide that has binding affinity for at least one opioid receptor a candidate opioid cyclic peptide; and
iii) testing any candidate opioid cyclic peptide using an in vitro or in vivo functional activity assay for agonist effects on the at least one opioid receptor, wherein
any candidate opioid cyclic peptide that has an affinity for at least one opioid receptor and that has agonist effects on the at least one opioid receptor is an opioid cyclic peptide.
2. The method of claim 1 , wherein the at least one opioid receptor is μ-n opioid receptor (MOR).
3. The method of claim 1 , wherein the combinatorial library is a positional-scanning synthetic combinatorial library.
4. The method of claim 1 , wherein the screening assay comprises a competitive binding assay.
5. The method of claim 1 , wherein the at least one opioid receptor is δ-opioid receptor (DOR).
6. The method of claim 1 , wherein the at least one opioid receptor is κ-opioid receptor (KOR).
7. The method of claim 1 , further comprising step iv) comprising administering an opioid cyclic peptide identified in step iii) to an animal and examining effects of the opioid cyclic peptide on respiration and analgesia in the animal.
8. A method of identifying opioid cyclic peptides comprising:
i) providing a combinatorial library comprising a plurality of distinct cyclic peptides of the general Formula II:
(SEQ ID NO: 18)
Tyr-Ala-Ser-Pro-Lys-cyclo-[Cys-Phe-Arg-XXXXX-Leu-
Ala-Cys]-Thr,
wherein each X is an amino acid selected from the group consisting of: D-amino acid, L-amino acid, non-natural synthetic amino acid, naturally occurring amino acid, and a mixture thereof;
ii) screening the plurality of cyclic peptides for binding affinity to u-opioid receptor (MOR), δ-opioid receptor (DOR), and κ-opioid receptor (KOR) in mammalian cells
using a screening assay to identify any cyclic peptide that has binding affinity for at least one opioid as a candidate opioid cyclic peptide; and
iii) testing any candidate opioid cyclic peptide using an in vitro or in vivo functional activity assay for antagonist effects on the at least one opioid receptor, wherein
any candidate opioid cyclic peptide that has an affinity for at least one opioid receptor and that has antagonist effects on the at least one opioid receptor is an opioid cyclic peptide.
9. The method of claim 8 , wherein the at least one opioid receptor is MOR.
10. The method of claim 8 , wherein the at least one opioid receptor is DOR.
11. The method of claim 8 , wherein the at least one opioid receptor is KOR.
12. The method of claim 8 , wherein the combinatorial library is a positional-scanning synthetic combinatorial library.
13. The method of claim 8 , wherein steps ii) and iii) comprise a competitive binding assay.
14. The method of claim 8 , further comprising step iv) comprising administering an opioid cyclic peptide identified in step iii) to an animal and examining effects of the opioid cyclic peptide on respiration and analgesia in the animal.