| 1. |
- Haugaard-Kedström, Linda M., et al.
(författare)
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Design, synthesis, and characterization of a single-chain peptide antagonist for the relaxin-3 receptor RXFP3
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 133:13, s. 4965-4974
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Tidskriftsartikel (refereegranskat)abstract
- Relaxin-3 is a two-chain disulfide-rich peptide that is the ancestral member of the relaxin peptide family and, together with its G protein-coupled receptor RXFP3, is highly expressed in the brain. Strong evolutionary conservation of relaxin-3 suggests a critical biological function and recent studies have demonstrated modulation of sensory, neuroendocrine, metabolic, and cognitive systems. However, detailed studies of central relaxin-3-RXFP3 signaling have until now been severely hampered by the lack of a readily available high-affinity antagonist for RXFP3. Previous studies have utilized a complex two-chain chimeric relaxin peptide, R3(B Delta 23-27)R/I5, in which a truncated relaxin-3 B-chain carrying an additional C-terminal Arg residue was combined with the insulin-like peptide S (INSL5) A-chain. In this study we demonstrate that, by replacing the native Cys in this truncated relaxin-3 B-chain with Ser, a single-chain linear peptide of 23 amino acids that retains high-affinity antagonism for RXFP3 can be achieved. In vivo studies demonstrate that this peptide, R3 B1-22R, antagonized relaxin-3/RXFP3 induced increases in feeding in rats after intracerebroventricular injection. Thus, R3 B1-22R represents an excellent tool for biological studies probing relaxin pharmacology and a lead molecule for the development of synthetically tractable, single-chain RXFP3 modulators for clinical use.
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| 2. |
- Hossain, M. Akhter, et al.
(författare)
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Synthesis, conformation, and activity of human insulin-like peptide 5 (INSL5)
- 2008
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 9:11, s. 1816-1822
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Tidskriftsartikel (refereegranskat)abstract
- Insulin-like peptide 5 (INSL5) was first identified through searches of the expressed sequence tags (EST) databases. Primary sequence analysis showed it to be a prepropeptide that was predicted to be processed in vivo to yield a two-chain sequence (A and B) that contained the insulin-like disulfide cross-links. The high affinity interaction between INSL5 and the receptor RXFP4 (GPCR142) coupled with their apparent coevolution and partially overlapping tissue expression patterns strongly suggest that INSL5 is an endogenous ligand for RXFP4. Given that the primary function of the INSL5–RXFP4 pair remains unknown, an effective means of producing sufficient quantities of this peptide and its analogues is needed to systematically investigate its structural and biological properties. A combination of solid-phase peptide synthesis methods together with regioselective disulfide bond formation were used to obtain INSL5. Both chains were unusually resistant to standard synthesis protocols and required highly optimized conditions for their acquisition. In particular, the use of a strong tertiary amidine, DBU, as Nα-deprotection base was required for the successful assembly of the B chain; this highlights the need to consider incomplete deprotection rather than acylation as a cause of failed synthesis. Following sequential disulfide bond formation and chain combination, the resulting synthetic INSL5, which was obtained in good overall yield, was shown to possess a similar secondary structure to human relaxin-3 (H3 relaxin). The peptide was able to inhibit cAMP activity in SK-N-MC cells that expressed the human RXFP4 receptor with a similar activity to H3 relaxin. In contrast, it had no activity on the human RXFP3 receptor. Synthetic INSL5 demonstrates equivalent activity to the recombinant-derived peptide, and will be an important tool for the determination of its biological function.
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| 3. |
- Hossain, M. Akhter, et al.
(författare)
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The structural and functional role of the B-chain C-terminal arginine in the relaxin-3 peptide antagonist, R3(B Delta 23-27)R/I5.
- 2009
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Ingår i: Chemical Biology and Drug Design. - : Wiley. - 1747-0277 .- 1747-0285. ; 73:1, s. 46-52
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Tidskriftsartikel (refereegranskat)abstract
- Relaxin-3, a member of the insulin superfamily, is involved in regulating stress and feeding behavior. It is highly expressed in the brain and is the endogenous ligand for the receptor RXFP3. As relaxin-3 also interacts with the relaxin receptor RXFP1, selective agonists and antagonists are crucial for studying the physiological function(s) of the relaxin-3/RXFP3 pair. The analog R3(B Delta 23-27)R/I5, in which a C-terminally truncated human relaxin-3 (H3) B-chain is combined with the INSL5 A-chain, is a potent selective RXFP3 antagonist and has an Arg residue remaining on the B-chain C-terminus as a consequence of the recombinant protein production process. To investigate the role of this residue in the RXFP3 receptor binding and activation, the analogs R3(B Delta 23-27)R/I5 and R3(B Delta 23-27)R containing the B-chain C-terminal Arg as well as R3(B Delta 23-27)/I5 and R3(B Delta 23-27), both lacking the Arg, were chemically assembled and their secondary structure and receptor activity assessed. The peptides generally had a similar conformation but those with the extra Arg residue displayed a significantly increased affinity for the RXFP3. Interestingly, in contrast to R3(B Delta 23-27)R and R3(B Delta 23-27)R/I5, the peptide R3(B Delta 23-27) is a weak agonist. This suggests that the C-terminal Arg, although increasing the affinity, alters the manner in which the peptide binds to the receptor and thereby prevents activation, giving R3(B Delta 23-27)R/I5 its potent antagonistic activity.
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