DREADD technology reveals major impact of Gq signalling on cardiac electrophysiology

Abstract

Aims Signalling via Gq-coupled receptors is of profound importance in many cardiac diseases such as hypertrophy and arrhythmia. Nevertheless, owing to their widespread expression and the inability to selectively stimulate such receptors in vivo, their relevance for cardiac function is not well understood. We here use DREADD technology to understand the role of Gq-coupled signalling in vivo in cardiac function. Methods and results We generated a novel transgenic mouse line that expresses a Gq-coupled DREADD (Dq) in striated muscle under the control of the muscle creatine kinase promotor. In vivo injection of the DREADD agonist clozapine-N-oxide (CNO) resulted in a dose-dependent, rapid mortality of the animals. In vivo electrocardiogram data revealed severe cardiac arrhythmias including lack of P waves, atrioventricular block, and ventricular tachycardia. Following Dq activation, electrophysiological malfunction of the heart could be recapitulated in the isolated heart ex vivo. Individual ventricular and atrial myocytes displayed a positive inotropic response and arrhythmogenic events in the absence of altered action potentials. Ventricular tissue sections revealed a strong co-localization of Dq with the principal cardiac connexin CX43. Western blot analysis with phosphor-specific antibodies revealed strong phosphorylation of a PKC-dependent CX43 phosphorylation site following CNO application in vivo. Conclusion Activation of Gq-coupled signalling has a major impact on impulse generation, impulse propagation, and coordinated impulse delivery in the heart. Thus, Gq-coupled signalling does not only modulate the myocytes’ Ca2+ handling but also directly alters the heart’s electrophysiological properties such as intercellular communication. This study greatly advances our understanding of the plethora of modulatory influences of Gq signalling on the heart in vivo.

Suppression of β1-Adrenoceptor Autoantibodies is Involved in the Antiarrhythmic Effects of Omega-3 Fatty Acids in Male and Female Hypertensive Rats

“…Taken together, it appears that cardiac β1-AR (G q -coupled receptors) might be involved in the regulation of Cx43 mediated electrical communication and are probably a critical factor in the maintenance of regular myocardial conduction [35,39], while the desensitization of β1-AR in association with the production of β1-AA may be crucial in the formation of an arrhythmogenic substrate involving aberrant Cx43 signaling as indicates our study. More attention should be paid to this issue when realizing that G q -coupled receptors interact with Cx43 at the intercalated disc [39] as well as likely contributing to the occurrence of G q -dependent arrhythmias.…”

In vivo cardiopulmonary impact of skeletal M3Dq DREADD expression: a pilot study

“…Rrs and Crs responses (averaged over 240 s) were recorded at 10-min intervals for 1-h post CNO injection. The dosage of CNO utilized was based on previous observations of mortality in mice expressing a Gq-linked designer G-protein coupled receptor selectively in striated muscle (heart and SKM) (Kaiser et al 2018 ).…”

Cardiovascular Research at the frontier of biomedical science

“…This includes knowledge of the differential regulation of neuronal sodium channels in the failing human myocardium, and an enhanced understanding of G proteincoupled receptors in the heart using designer receptors solely activated by designer drugs (DREADD) technology. 35,36 One perhaps historically under-recognized aspect of cardiovascular biology is the effects of the coronary microvasculature, implicated in ischaemic heart disease. In March 2020, this burgeoning and fascinating topic was thoroughly explored in a Cardiovascular Research Spotlight Issue on Coronary microvascular dysfunction: examining the basic, translational, and clinical aspects of this emerging area.…”