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 4

The Popeye domain functions as a cyclic nucleotide-binding domain.

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The Popeye domain functions as a cyclic nucleotide-binding domain. (A) S...
(A) Secondary structure of human cAMP-dependent protein kinase type II-β regulatory subunit (PRKAR2B) and structural prediction of the Popeye domain of human POPDC1. Pink rods, α helices; yellow arrows, β strands; pink underlay, PBC. (B) Western blot detection of chick Popdc1 after affinity precipitation of cardiac tissue extracts incubated with cAMP-agarose. Bound Popdc1 protein was eluted with increasing amounts of cAMP. P, pellet; S, supernatant; T, total protein; C, control incubation using ethanolamine-agarose. (C) Western blot of Cos-7 cells transfected with Popdc1, Popdc2, and Popdc3 cDNAs. Shown are total protein and protein bound to cAMP-agarose or ethanolamine (EA) agarose. Brackets denote differentially glycosylated Popdc proteins; asterisks denote nonglycosylated form of Popdc proteins; arrowhead denotes unspecific immunoreactive protein. (D) 3D model of the Popeye domain of human POPDC1. Invariant amino acids are colored red. The cAMP moiety is shown as CPK model. (E) Enlargement of the predicted cAMP binding site. Predicted hydrogen bonds between cAMP and the DSPE and FQVT sequence motifs are shown as dashed lines. (F) Western blot of cAMP-agarose precipitations of Cos-7 cells transfected with cDNAs encoding Popdc1 and Popdc1D200A, Popdc1P202A, Popdc1E203A, or Popdc1V217F mutants. (G) Western blot of cAMP-agarose precipitations of Cos-7 cells transfected with cDNAs encoding Popdc2 or Popdc2D184A mutant. (H) Radioligand binding assay using [3H]-cAMP and recombinant C terminus of Popdc1. Binding was competed with increasing concentrations of free unlabeled cAMP and cGMP, respectively.