Conserved expression and functions of PDE4 in rodent and human heart

Abstract

PDE4 isoenzymes are critical in the control of cAMP signaling in rodent cardiac myocytes. Ablation of PDE4 affects multiple key players in excitation–contraction coupling and predisposes mice to the development of heart failure. As little is known about PDE4 in human heart, we explored to what extent cardiac expression and functions of PDE4 are conserved between rodents and humans. We find considerable similarities including comparable amounts of PDE4 activity expressed, expression of the same PDE4 subtypes and splicing variants, anchoring of PDE4 to the same subcellular compartments and macromolecular signaling complexes, and downregulation of PDE4 activity and protein in heart failure. The major difference between the species is a fivefold higher amount of non-PDE4 activity in human hearts compared to rodents. As a consequence, the effect of PDE4 inactivation is different in rodents and humans. PDE4 inhibition leads to increased phosphorylation of virtually all PKA substrates in mouse cardiomyocytes, but increased phosphorylation of only a restricted number of proteins in human cardiomyocytes. Our findings suggest that PDE4s have a similar role in the local regulation of cAMP signaling in rodent and human heart. However, inhibition of PDE4 has ‘global’ effects on cAMP signaling only in rodent hearts, as PDE4 comprises a large fraction of the total cardiac PDE activity in rodents but not in humans. These differences may explain the distinct pharmacological effects of PDE4 inhibition in rodent and human hearts.Electronic supplementary materialThe online version of this article (doi:10.1007/s00395-010-0138-8) contains supplementary material, which is available to authorized users.

Phosphodiesterase 4B in the cardiac L-type Ca2+ channel complex regulates Ca2+ current and protects against ventricular arrhythmias in mice

“…Similar to what was reported earlier in the rat (34), PDE4 activity in the mouse ventricle was due to the expression of PDE4A, PDE4B, and PDE4D variants. The migra- tion on SDS/PAGE of these variants corresponds to long forms, and although only one immunoreactive band was detected in each case, this band may correspond to the comigration of several long forms, as demonstrated earlier for PDE4D (23,24,29).…”

“…IP of PDE4 subtypes was performed as described previously (24). In brief, cell and tissue extracts, prepared as described in "Preparation of protein extracts," were precleared for 1 hour using 50 μl protein G-Sepharose, followed by a second centrifugation at 20,000 g and 4°C for 10 minutes.…”

“…So far, of these genes, most of our knowledge in the heart concerns the PDE4D gene. Long variants of this gene expressed in the heart include the isoforms PDE4D3, PDE4D5, PDE4D8, and PDE4D9 (23,24). PDE4D5, PDE4D8, and PDE4D9 were shown to differentially interact with β 1 -AR and β 2 -AR subtypes in neonatal cardiomyocytes, either directly or by binding to β-arrestin (25)(26)(27).…”

PDE4B mediates local feedback regulation of β1-adrenergic cAMP signaling in a sarcolemmal compartment of cardiac myocytes

“…Here, we show that during bAR stimulation, PKA phosphorylates and activates this PDE4B isoform. Its mobility in SDS/PAGE gels is identical to the PDE4B isoforms identified in the adult mouse, rat and human heart (Abi-Gerges et al, 2009;Richter et al, 2011). Thus, any regulation of this isoform is likely conserved and relevant to human cardiac physiology.…”

“…Of these, PDE4 isoforms are crucial in shaping global cAMP signals arising from b 1 AR and b 2 AR stimulation in cardiac myocytes in rodents and in humans Molina et al, 2012). The PDE4 family is encoded by four genes (PDE4A, PDE4B, PDE4C and PDE4D); however, only PDE4A, PDE4B and PDE4D are expressed in cardiac myocytes Richter et al, 2011). These three genes encode multiple isoforms generated through alternative splicing and use of alternative promoters/transcription start sites (Bender and Beavo, 2006;Jin and Conti, 2002).…”