The activity of prolactin releasing peptide correlates with its helicity

Abstract

The prolactin releasing peptide (PrRP) is involved in regulating food intake and body weight homeostasis, but molecular details on the activation of the PrRP receptor remain unclear. C-terminal segments of PrRP with 20 (PrRP20) and 13 (PrRP8-20) amino acids, respectively, have been suggested to be fully active. The data presented herein indicate this is true for the wildtype receptor only; a 5-10-fold loss of activity was found for PrRP8-20 compared to PrRP20 at two extracellular loop mutants of the receptor. To gain insight into the secondary structure of PrRP, we used CD spectroscopy performed in TFE and SDS. Additionally, previously reported NMR data, combined with ROSETTANMR, were employed to determine the structure of amidated PrRP20. The structural ensemble agrees with the spectroscopic data for the full-length peptide, which exists in an equilibrium between α- and 310-helix. We demonstrate that PrRP8-20’s reduced propensity to form an α-helix correlates with its reduced biological activity on mutant receptors. Further, distinct amino acid replacements in PrRP significantly decrease affinity and activity but have no influence on the secondary structure of the peptide. We conclude that formation of a primarily α-helical C-terminal region of PrRP is critical for receptor activation.

Prolactin-Releasing Peptide: Physiological and Pharmacological Properties

“…Two isoforms of PrRP with either 20 or 31 amino acids sharing identical C-termini showed comparable in vitro and in vivo activity [1]. Several SAR studies with PrRP analogs were performed [31,56,57,58]. No study about selective antagonists of PrRP has been published yet, but in 2010, Otsuka Pharmaceuticals patented nonpeptide heterocyclic antagonists derived from tetrahydropyridol [4,3-d]pyrimidinone developed for stress-related diseases (reviewed in [59]).…”

“…DeLuca et al performed a structural study based on NMR and CD spectroscopy, where they determined the α-helical conformation in trifluoroethanol of the C-terminal sequence of PrRP20 [57]. Shorter PrRP20 analogs, PrRP(4–20), PrRP13 (PrRP(8–20)), and heptapeptide PrRP(14–20), decreased the stability of the helical segment and their biological activity was reduced.…”

“…Shorter PrRP20 analogs, PrRP(4–20), PrRP13 (PrRP(8–20)), and heptapeptide PrRP(14–20), decreased the stability of the helical segment and their biological activity was reduced. Therefore, this stable C-terminal α-helical structure facilitates ligand recognition by the receptor and enables its activation [57].…”

Integrating Solid-State NMR and Computational Modeling to Investigate the Structure and Dynamics of Membrane-Associated Ghrelin

“…The authors’ models were supported by CD data collected in water, dodecylphosphocholine micelles, SDS micelles, and TFE. For both forms of ghrelin, the helicity increased significantly in SDS micelles and TFE [ 23 ] A similar trend was observed for the prolactin releasing peptide (PrRP), another peptide that plays a role in food intake and body weight homeostasis [ 85 ]. In the case of PrRP, it was demonstrated that the peptide likely exists in a conformational equilibrium between α- and 3 10 -helix, and the helical propensity of the peptide is essential for its ability to activate the PrRP receptor, another GPCR.…”

The Structural Basis of Peptide Binding at Class A G Protein-Coupled Receptors

“…Several peptide hormones have been examined to understand their structure via NMR or CD in solution. These include motilin [ 146 ], prolactin-releasing peptide [ 147 , 148 ], vasopressin [ 149 ], relaxin [ 150 , 151 ], and somatostatin analogues [ 152 , 153 , 154 , 155 ]. In contrast, relatively few examples of peptides exist, which are studied in both their solution and bound states.…”