Characterisation and expression of β1-, β2- and β3-adrenergic receptors in the fathead minnow (Pimephales promelas)

Abstract

Complimentary DNAs for three beta-adrenergic receptors (βARs) were isolated and characterised in the fathead minnow. The encoded proteins of 402 (β(1)AR), 397 (β(2)AR) and 434 (β(3)AR) amino acids were homologous to other vertebrate βARs, and displayed the characteristic seven transmembrane helices of G Protein-coupled receptors. Motifs and amino acids shown to be important for ligand binding were conserved in the fathead minnow receptors. Quantitative RT-PCR revealed the expression of all receptors to be highest in the heart and lowest in the ovary. However, the β(1)AR was the predominant subtype in the heart (70%), and β(3)AR the predominant subtype in the ovary (53%). In the brain, β(1)AR expression was about 200-fold higher than that of β(2)- and β(3)AR, whereas in the liver, β(2)AR expression was about 20-fold and 100-fold higher than β(3)- and β(1)AR expression, respectively. Receptor gene expression was modulated by exposure to propranolol (0.001-1mg/L) for 21 days, but not in a consistent, concentration-related manner. These results show that the fathead minnow has a beta-adrenergic receptor repertoire similar to that of mammals, with the molecular signatures required for ligand binding. An exogenous ligand, the beta-blocker propranolol, is able to alter the expression profile of these receptors, although the functional relevance of such changes remains to be determined. Characterisation of the molecular targets for beta-blockers in fish will aid informed environmental risk assessments of these drugs, which are known to be present in the aquatic environment.

β3‐AR and the vertebrate heart: a comparative view

“…) and of the fathead minnow ( Pimephales promelas ) (Giltrow et al . ). In fathead minnow, β 3 ‐ARs showed the highest expression in the heart, followed by liver, ovary, brain, gills, red blood cells and adipose tissue (Giltrow et al .…”

“…In fathead minnow, β 3 ‐ARs showed the highest expression in the heart, followed by liver, ovary, brain, gills, red blood cells and adipose tissue (Giltrow et al . ). In amphibians, to the best of our knowledge, only Mazza et al .…”

Receptors rather than signals change in expression in four physiological regulatory networks during evolutionary divergence in threespine stickleback

“…We found that freshwater sticklebacks have higher expression of beta-2 adrenergic receptors (adrb2a) in the brain. These receptors are expressed in a variety of tissues in fish, including the brain [Pimephales promelas (Giltrow et al 2011)], but their role in the central nervous system is less studied. Our results uncover a potential new association between this receptor and stress physiology, and suggest that the functional implication of their higher expression in more aggressive, more active, less social and less reactive fish (Di Poi et al 2014, 2016 should be further studied.…”

Uptake and Effects of the Beta‐Adrenergic Agonist Salbutamol in Fish: Supporting Evidence for the Fish Plasma Model

“…Adrenergic pathways and receptors, particularly beta-adrenergic receptors as the phylogenetic older ones, are conserved in fish (Owen et al 2007;Giltrow et al 2011;Fabbri and Moon 2016). Hence, specific receptor-related effects may occur in fish as postulated by the FPM.…”