Involvement of PDE2 in a Localized Regulation of the L-Type Ca2+ Channels by Progesterone

Abstract

We have demonstrated that a nitric oxide production induced by stimulation of progesterone (P4) receptor suppresses cAMP-stimulated L-type Ca2+ currents (ICa,L) through an increase in cytosolic cGMP, which may be related to the sex difference of QT intervals and risks of arrhythmia. We here seek the underlying mechanisms on the regulation of ICa,L in patch-clamped guinea pig ventricular myocytes. An external application of P4 (100 nM) suppressed ICa,L about 30 % (100 nM P4; 58±4 %, n=13, without P4 (time control); 84±2 %, n=5). In the presence of a specific PDE2 inhibitor, EHNA (30 μM), P4 suppressed ICa,L to 84±5 % (n=7), which is the same extent with the time control. Pharmacological studies revealed that hydrolysis of cAMP by a cGMP-stimulated phosphodiesterase (PDE2) involves in the P4-induced ICa,L suppression. However the underlying mechanisms of the ICa,L suppression remain to be solved. Thus, we employed sucrose density gradient fractionation experiments to examine localization of the molecules in this system, which is dependent of lipid-raft composition. We found that substantial fraction of CaV1.2 and PDE2 clustered in caveolae fractions, but PDE3 clustered in extra-caveolae fractions. Furthermore, a proximity ligation assay (Olink) revealed that CaV1.2 interacted both with PDE2 and PDE3, but there was no interaction between PDE2 and PDE3. These results suggest that PDE2 and the L-type Ca2+ channel co-localizes at the caveolae for the non-genomic regulation of ICa,L by P4.