GPCR-dependent biasing of GIRK channel signaling dynamics by RGS6 in mouse sinoatrial nodal cells

Allison Anderson, Ikuo Masuho, Ezequiel Marron Fernandez De Velasco, Atsushi Nakano, Lutz Birnbaumer, Lutz Birnbaumer, Kirill A. Martemyanov, Kevin Wickman

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


How G protein-coupled receptors (GPCRs) evoke specific biological outcomes while utilizing a limited array of G proteins and effectors is poorly understood, particularly in native cell systems. Here, we examined signaling evoked by muscarinic (M 2R) and adenosine (A 1R) receptor activation in the mouse sinoatrial node (SAN), the cardiac pacemaker. M 2R and A 1R activate a shared pool of cardiac G protein-gated inwardly rectifying K + (GIRK) channels in SAN cells from adult mice, but A 1R-GIRK responses are smaller and slower than M 2R-GIRK responses. Recordings from mice lacking Regulator of G protein Signaling 6 (RGS6) revealed that RGS6 exerts a GPCR-dependent influence on GIRK-dependent signaling in SAN cells, suppressing M 2R-GIRK coupling efficiency and kinetics and A 1R-GIRK signaling amplitude. Fast kinetic bioluminescence resonance energy transfer assays in transfected HEK cells showed that RGS6 prefers Gα o over Gα i as a substrate for its catalytic activity and that M 2R signals preferentially via Gα o, while A 1R does not discriminate between inhibitory G protein isoforms. The impact of atrial/SAN-selective ablation of Gα o or Gα i2 was consistent with these findings. Gα i2 ablation had minimal impact on M 2R-GIRK and A 1R-GIRK signaling in SAN cells. In contrast, Gα o ablation decreased the amplitude and slowed the kinetics of M 2R-GIRK responses, while enhancing the sensitivity and prolonging the deactivation rate of A 1R-GIRK signaling. Collectively, our data show that differences in GPCR-G protein coupling preferences, and the Gα o substrate preference of RGS6, shape A 1R- and M 2R-GIRK signaling dynamics in mouse SAN cells.

Original languageEnglish (US)
Pages (from-to)14522-14531
Number of pages10
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number25
StatePublished - Jun 23 2020

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Dr. C. David Weaver and Dr. Corey Hopkins for providing ML297, Nickolas Skamangas for technical support, and Hannah Oberle and Mehrsa Zahiremami for exceptional care of the mouse colony. This work was supported by NIH Grants HL105550 (to K.W. and K.A.M.), R21 HL124503 (to A.N.), and F31 HL139090 (A.A.) and by NIH Intramural Research Program Project Grant Z01-ES-101643 (to L.B.).

Publisher Copyright:
© 2020 National Academy of Sciences. All rights reserved.


  • Adenosine
  • G protein
  • Heart rate
  • Kir3
  • Muscarinic
  • Heart Rate/physiology
  • Action Potentials/physiology
  • Isolated Heart Preparation
  • RGS Proteins/genetics
  • Humans
  • Sinoatrial Node/cytology
  • Mice, Knockout
  • Signal Transduction/physiology
  • Receptor, Adenosine A1/metabolism
  • Animals
  • HEK293 Cells
  • Receptor, Muscarinic M2/metabolism
  • Receptors, G-Protein-Coupled/metabolism
  • Mice
  • Primary Cell Culture
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels/genetics

PubMed: MeSH publication types

  • Research Support, N.I.H., Intramural
  • Journal Article
  • Research Support, N.I.H., Extramural


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