Phosphodiesterase Type 4 anchoring regulates cAMP signaling to Popeye domain-containing proteins

Abstract

Cyclic AMP is a ubiquitous second messenger used to transduce intracellular signals from a variety of Gs-coupled receptors. Compartmentalisation of protein intermediates within the cAMP signaling pathway underpins receptor-specific responses. The cAMP effector proteins protein-kinase A and EPAC are found in complexes that also contain phosphodiesterases whose presence ensures a coordinated cellular response to receptor activation events. Popeye proteins are the most recent class of cAMP effectors to be identified and have crucial roles in cardiac pacemaking and conduction. We report the first observation that Popeye proteins exist in complexes with members of the PDE4 family in cardiac myocytes thus restricting cAMP signaling. We show that POPDC1 preferentially binds the PDE4A sub-family via a specificity motif in the PDE4 UCR1 region and that PDE4s bind to the Popeye domain of POPDC1 in a region known to be susceptible to a mutation that causes human disease. Using a cell-permeable disruptor peptide that displaces the POPDC1-PDE4 complex we show that PDE4 activity localized to POPDC1 is essential to maintain action potential duration in beating cardiac myocytes.

Popeye Domain-Containing Protein 1 Scaffolds a Complex of Adenylyl Cyclase 9 and the Two-Pore-Domain Potassium Channel TREK-1 in Heart

“…It is unlikely that the impaired regulation of TREK-1 alone is sufficient to explain the strong phenotype of the Popdc1 and -2 null mutants, particularly when compared to phenotypes of Kcnk2 or Adcy9 deletions in mice. Recently, an interaction of POPDC1 and PDE4 isoforms have been described ( 54 ). A cell-permeable peptide that disrupts the POPDC1:PDE4 complex caused a reduction in cycle length of spontaneous Ca 2+ transients in mouse SA nodes.…”

The Role of POPDC Proteins in Cardiac Pacemaking and Conduction

“…A recent study by Tibbo et al (2020) showed that POPDC1 proteins, similar to other cAMP effectors, also form a complex with PDE4s, particularly and preferably with the PDE4A isoform [111]. The study concluded that POPDC1-PDE4A complex formation serves as a protective measure, which prevents inappropriate cAMP binding to the Popeye domain under basal conditions.…”

“…The study concluded that POPDC1-PDE4A complex formation serves as a protective measure, which prevents inappropriate cAMP binding to the Popeye domain under basal conditions. Experimentally orchestrated disruption of PDE4 and POPDC1 interaction resulted in a decreased interaction between POPDC1 and TREK1 as well as causing a prolongation of AP duration in isolated ventricular myocytes [111].…”

“…While the precise molecular interactions still need to be worked out, the protein complex in which POPDC proteins are probably working to modulate action potential duration is gradually emerging. TREK-1 binds to the proximal part of the Popeye domain and binding may be adjacent or overlapping with that of PDE4 [29,111]. Thus, probably, these three proteins are in a common complex.…”

“…Currently, there is no evidence for a prolongation of the QRS complex in the mouse, while in zebrafish popdc1 morphants, a reduction in action potential duration has been described [143]. Significantly, action potential prolongation was observed in rabbit ventricular myocytes when the interaction of PDE4A and POPDC1 was blocked by a peptide [111]. These findings indicate that it is probably important to choose the right animal model to find evidence for a functional link between POPDC1 mutations and QT interval and QRS duration.…”