Popeye domain containing proteins are essential for stress-mediated modulation of cardiac pacemaking in mice
Alexander Froese, … , Larissa Fabritz, Thomas Brand
Alexander Froese, … , Larissa Fabritz, Thomas Brand
Published February 22, 2012
Citation Information: J Clin Invest. 2012;122(3):1119-1130. https://doi.org/10.1172/JCI59410.
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Research Article

Popeye domain containing proteins are essential for stress-mediated modulation of cardiac pacemaking in mice

Abstract

Cardiac pacemaker cells create rhythmic pulses that control heart rate; pacemaker dysfunction is a prevalent disorder in the elderly, but little is known about the underlying molecular causes. Popeye domain containing (Popdc) genes encode membrane proteins with high expression levels in cardiac myocytes and specifically in the cardiac pacemaking and conduction system. Here, we report the phenotypic analysis of mice deficient in Popdc1 or Popdc2. ECG analysis revealed severe sinus node dysfunction when freely roaming mutant animals were subjected to physical or mental stress. In both mutants, bradyarrhythmia developed in an age-dependent manner. Furthermore, we found that the conserved Popeye domain functioned as a high-affinity cAMP-binding site. Popdc proteins interacted with the potassium channel TREK-1, which led to increased cell surface expression and enhanced current density, both of which were negatively modulated by cAMP. These data indicate that Popdc proteins have an important regulatory function in heart rate dynamics that is mediated, at least in part, through cAMP binding. Mice with mutant Popdc1 and Popdc2 alleles are therefore useful models for the dissection of the mechanisms causing pacemaker dysfunction and could aid in the development of strategies for therapeutic intervention.

Authors

Alexander Froese, Stephanie S. Breher, Christoph Waldeyer, Roland F.R. Schindler, Viacheslav O. Nikolaev, Susanne Rinné, Erhard Wischmeyer, Jan Schlueter, Jan Becher, Subreena Simrick, Franz Vauti, Juliane Kuhtz, Patrick Meister, Sonja Kreissl, Angela Torlopp, Sonja K. Liebig, Sandra Laakmann, Thomas D. Müller, Joachim Neumann, Juliane Stieber, Andreas Ludwig, Sebastian K. Maier, Niels Decher, Hans-Henning Arnold, Paulus Kirchhof, Larissa Fabritz, Thomas Brand

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Figure 5

Interaction of Popdc proteins with the 2-pore channel TREK-1.

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Interaction of Popdc proteins with the 2-pore channel TREK-1. (A) Relati...
(A) Relative current amplitudes of TASK-1 alone or in the presence of Popdc2 were assayed in Xenopus oocytes 48–72 hours after injection (n = 28–31). Error bars in A and C–E are SEM. (B) Example of the measurement of TREK-1–mediated outward current after injection of TREK-1 cRNA alone (gray curve) or in the presence of Popdc1 (black curve) in Xenopus oocytes. (C) Relative current amplitudes of TREK-1 alone or in the presence of Popdc1, Popdc2, or Popdc3 (n = 14–22). *P < 0.05. (D) Relative TREK-1 current amplitudes in the presence or absence of Popdc2. The oocytes were incubated for 48 hours with or without theophylline (n = 17–32). *P < 0.05. (E) Quantification of the relative surface expression of HA-tagged rat TREK-1b in the presence or absence of mouse Popdc2 (n = 27 and 19, respectively). ni, noninjected control oocytes (n = 12). *P < 0.05. (F and G) Immunostaining of Popdc1 (red) or TREK-1 (green) transfected individually (F) or both together (G) into Cos-7 cells. Nuclei were counterstained with DAPI. Scale bars: 10 μm. (H) Example of a GST pulldown experiment using the C terminus of Popdc1 fused to GST and Flag-tagged human TREK-1. GST-E12 and GST proteins were used as controls.