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Pharmacological Characterisation of PACAP‐responsive Receptors Reveals Signalling Bias and Probe‐dependent Antagonism
Author(s) -
Tasma Zoe,
Hay Debbie,
Walker Christopher
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.02181
Subject(s) - receptor , vasoactive intestinal peptide , g protein coupled receptor , adenylate kinase , neuropeptide , microbiology and biotechnology , signal transduction , pituitary adenylate cyclase activating peptide , g protein , chemistry , biology , endocrinology , biochemistry
Pituitary adenylate cyclase‐activating peptide (PACAP) is a neuropeptide which exists in two biologically active forms; PACAP‐27 and PACAP‐38. PACAP is widely expressed in the brain and periphery where it is involved in many physiological processes including pain, inflammation, stress and anxiety. PACAP potently activates three different G protein‐coupled receptors (GPCRs); the PAC 1 receptor, the VPAC 1 receptor and VPAC 2 receptor. The VPAC receptors are co‐receptors for PACAP and vasoactive intestinal peptide (VIP). The PAC 1 receptor has several known splice variants in the N‐terminal domain, which include the PAC 1n receptor (full N‐terminus) and the PAC 1s receptor (21 amino acid N‐terminal deletion). To develop therapeutics targeting the PACAP system, it is essential to understand how these receptors signal and how this signalling is inhibited. Here we pharmacologically characterised the signalling capabilities of PACAP‐responsive receptors and how these responses were blocked by antagonists. The pharmacology of the human PAC 1n , PAC 1s , VPAC 1 , VPAC 2 receptors were examined in transfected Cos7 cells. Using concentration‐response curves, the ability of PACAP and related peptides to stimulate cAMP, IP 1 , pAkt, pERK and pCREB responses were measured. Signalling bias was then quantified. The ability of multiple antagonists to block PACAP‐38, PACAP‐27 or VIP‐induced cAMP responses at PACAP‐responsive receptors was then determined. PACAP‐responsive receptors stimulated activation of all signalling molecules measured. However, only limited signalling bias was observed. For example, VIP was 4‐fold biased towards cAMP production over IP 1 production at the PAC 1n receptor. Interestingly, the PAC 1n and PAC 1s receptors displayed distinct pharmacology. At the PAC 1s receptor, VIP was found to be 20‐fold more potent than at the PAC 1n receptor. Probe‐ or agonist‐dependent antagonism was observed at the PAC 1n and PAC 1s receptors. Both VIP and PACAP‐27 were more potently antagonised than PACAP‐38 by the antagonists PACAP 6–38 and M65. The distinct pharmacological profile displayed by the PAC 1s receptor, suggests that it can act as a dual receptor for VIP and PACAP under specific conditions. Furthermore, differences in antagonist pharmacology at PACAP‐responsive receptors suggests the effectiveness of blocking a signalling pathway can be influenced by which endogenous agonist is present. These effects have potential implications for the development and effectiveness of drugs targeting the PAC 1 receptor. Support or Funding Information This research is supported by grants from the Royal Society of New Zealand Marsden Fund (RSNZ) and the Health Research Council of New Zealand (HRC).