Peptide P518 GPCR Assays
Background of P518 Receptor
As we all know, peptide P518 is consistent with 26RFa, a novel RFamide-related peptide. Studies revealed that these RFamide peptides play compelling roles in neuroendocrine, behavioral, and autonomic functions. Furthermore, peptide P518 is widely distributed in many tissues and organs. It is mainly expressed in different brain regions, thyroid and parathyroid glands, coronary arteries, colon, large intestine, testis, bladder, and prostate. The high affinity of P518 for GPR103 suggested that P518 may be the endogenous ligand of GPR103.
Distribution and Functions of GPR103
GPR103 (also known as SP9155 and AQ27) is a Gαi/o and Gαq protein-coupled receptor originally cloned from a human brain cDNA library. GPR103 is actively expressed in the brain, heart, kidney, retina, and testis. Several findings suggest that GPR103 is closely related to the regulation of bone formation in mammals.
Signaling of GPR103
The GPR103 receptor is coupled to different proteins and is involved in multiple signaling pathways.
| Receptor | Gene | Mechanism | Agonists | Antagonists |
| GPR103 Receptor | QRFPR |
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Published Data
| Paper Title |
Anxiolytic effect of the GPR103 receptor agonist peptide P550 (homolog of neuropeptide 26RFa) in mice. Involvement of neurotransmitters |
| Journal |
Peptides |
| Published | 2016 |
| Abstract | GPR103 is an orphan receptor with a single encoding gene in humans, while two isoforms exist in rodents, termed GPR103A and GPR103B, respectively. 43RFa and 26RFa bind both isoforms with analogous affinity. GPR103 is present in multiple brain regions, including paraventricular and magnocellular hypothalamic nuclei, striatum, lateral septum (LS), medial supramapillary nuclei, and rodent brainstem. The GPR103/43RFa/26RFa system is closely associated with multiple physiological functions, including bone formation, lipogenesis, food intake, energy homeostasis, insulin secretion, blood pressure, and motor activity. However, the function of GPR103 receptors in anxiety is currently unknown. |
| Result |
The first aim of this study was to reveal the role of the GPR103 receptor in anxiety behavior. Mice were processed with the peptide P550, which has approximate activity at the GPR103 receptor as the neuropeptide 26RFa. Anxiety behavior was studied by the elevated plus maze paradigm. Another aim of this study was to explain the potential neurotransmission. Therefore, mice were processed with specific antagonists of different receptors. The results showed that peptide P550 reduces anxiety behavior in mice in the test. Furthermore, it is worth noting that the study also suggested that GABAA-ergic as well as α- and β-adrenergic transmissions are implicated in this effect, while 5-hydroxytryptamine 1 & 5-hydroxytryptamine 2 serotonergic as well as D2, D3, D4 dopaminergic mechanisms may not be involved in the process.
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Fig.1 The anxiolytic action of P550 in the elevated plus maze. (Palotai, 2016)
Reference
- Palotai, M.; Telegdy, G. Anxiolytic effect of the GPR103 receptor agonist peptide P550 (homolog of neuropeptide 26RFa) in mice. Involvement of neurotransmitters. Peptides. 2016; 82: 20-25.
