Open AccessA nonolfactory shark adenosine receptor activates CFTR with unique pharmacology and structural features
Author(s) -
Sumeet Bhanot,
Gabriele Hemminger,
Cole L. Martin,
Stephen G. Aller,
Jeffrey YiLin Forrest
Publication year - 2021
Publication title -
american journal of physiology. cell physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.432
H-Index - 181
eISSN - 1522-1563
pISSN - 0363-6143
DOI - 10.1152/ajpcell.00481.2020
Subject(s) - adenosine , adenosine receptor , cystic fibrosis transmembrane conductance regulator , medicine , chemistry , endocrinology , chloride channel , receptor , agonist , g protein coupled receptor , biology , biochemistry , cystic fibrosis
Adenosine receptors (ADORs) are G protein-coupled purinoceptors that have several functions including regulation of chloride secretion via cystic fibrosis transmembrane conductance regulator (CFTR) in human airway and kidney. We cloned an ADOR from Squalus acanthias (shark) that likely regulates CFTR in the rectal gland. Phylogenic and expression analyses indicate that elasmobranch ADORs are nonolfactory and appear to represent extant predecessors of mammalian ADORs. We therefore designate the shark ADOR as the A 0 receptor. We coexpressed A 0 with CFTR in Xenopus laevis oocytes and characterized the coupling of A 0 to the chloride channel. Two-electrode voltage clamping was performed, and current-voltage ( I-V ) responses were recorded to monitor CFTR status. Only in A 0 - and CFTR-coinjected oocytes did adenosine analogs produce a significant concentration-dependent activation of CFTR consistent with its electrophysiological signature. A pharmacological profile for A 0 was obtained for ADOR agonists and antagonists that differed markedly from all mammalian ADOR subtypes [agonists: R-phenyl-isopropyl adenosine (R-PIA) > S-phenyl-isopropyl adenosine (S-PIA) > CGS21680 > N 6 -cyclopentyladenosine (CPA) > 2-chloroadenosine (2ClAdo) > CV1808 = N 6 -[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine (DPMA) > N -ethyl-carboxyl adenosine (NECA); and antagonists: 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) > PD115199 > 1,3-dimethyl-8-phenylxanthine (8PT) > CGS15943]. Structures of human ADORs permitted a high-confidence homology model of the shark A 0 core that revealed unique structural features of ancestral receptors. We conclude that 1 ) A 0 is a novel and unique adenosine receptor ancestor by functional and structural criteria; 2 ) A 0 likely activates CFTR in vivo, and this receptor activates CFTR in oocytes, indicating an evolutionary coupling between ADORs and chloride secretion; and 3 ) A 0 appears to be a nonolfactory evolutionary ancestor of all four mammalian ADOR subtypes.