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 domain containing (POPDC) 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 POPDC proteins exist in complexes with members of the PDE4 family in cardiac myocytes. 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 modulates cycle length of spontaneous Ca 2+ transients firing in intact mouse sinoatrial nodes.

Differential Effects of Mutations of Popeye Domain Containing Proteins on Heteromeric Interaction and Membrane Trafficking

“…58,59 Indeed, POPDC1 has been shown to form functionally important interactions with cAMP pathway proteins such as PDE4, AC9, and TREK-1 in the heart, the disruption of which may impact calcium transients, β-adrenergic signalling, and ion channel function. 12,13 Such an effect could explain the cardiac arrhythmias which have been observed in many patients carrying BVES or POPDC2 variants 11,14,17–21 and may also be responsible for the muscular dystrophy phenotype associated with POPDC mutations, although the link to cAMP signalling has not yet been established in the case of skeletal muscle. However, POPDC1 and POPDC2 have been reported to interact with a number of proteins linked to sarcolemmal stability or repair such as dystrophin, 11 dysferlin, 11 Xin-related protein 1, 45 annexin A5, 45 anoctamin 5, 43 and caveolin-3.…”

“…Recently, a binding site for PDE4 was mapped to the b3-strand of POPDC1. 12 By analogy, we hypothesize that the V183F mutation may potentially affect a binding site for an unknown interaction partner, which is essential for skeletal muscle but dispensable for the heart. Given the orientation of V183 into the core of the Popeye domain this would require the mutation to cause allosteric alterations to the protein.…”

“…10,11 POPDC proteins function as a novel class of cAMP effector proteins 3 and interactions with other proteins involved in cAMP signalling such as phosphodiesterase 4 (PDE4) and adenylyl cyclase 9 (AC9) have recently been described. 12,13…”

“…10,11 POPDC proteins function as a novel class of cAMP effector proteins 3 and interactions with other proteins involved in cAMP signalling such as phosphodiesterase 4 (PDE4) and adenylyl cyclase 9 (AC9) have recently been described. 12,13 A sizable number of patients who carry pathogenic variants in POPDC genes have been identified and suffer from heart and/or muscle disease. 11,[14][15][16][17] Patients carrying BVES mutations develop a recessive form of limb-girdle muscular dystrophy (LGMDR25), with most patients also suffering from cardiac arrhythmia (sinus bradycardia, sinus tachycardia, or atrioventricular (AV)-block).…”

POPDC1 scaffolds a complex of adenylyl cyclase 9 and the potassium channel TREK‐1 in heart

“…Recently, an interaction of POPDC1 and PDE4 isoforms has been described (Tibbo et al, 2022). A cell-permeable peptide that disrupts the POPDC1:PDE4 complex caused a reduction in the cycle length of spontaneous Ca 2+ transients in mouse SA nodes.…”