Aim: TRPV4-C1 heteromeric channels contribute to store-operated Ca(2+) entry in vascular endothelial cells. However, the negative regulation of these channels is not fully understood. This study was conducted to investigate the inhibitory effect of PKG1α on TRPV4-C1 heteromeric channels.
Methods: Immuno-fluorescence resonance energy transfer (FRET) was used to explore the spatial proximity of PKG1α and TRPC1. Phosphorylation of endogenous TRPC1 was tested by phosphorylation assay. [Ca(2+)]i transients and cation current in MAECs were assessed with Fura-2 fluorescence and whole-cell recording, respectively. In addition, rat mesenteric arteries segments were prepared, and vascular relaxation was examined with wire myography.
Results: In immuno-FRET experiments, after exposure of these cells to 8-Br-cGMP, more PKG1α was observed in the plasma membrane, and PKG1α and TRPC1 were observed to be in closer proximity. TAT-TRPC1(S172) and TAT-TRPC1(T313) peptide fragments, which contain the PKG targeted residues Ser172 and Thr313, respectively, were introduced into isolated endothelial cells to abrogate the translocation of PKG1α. Furthermore, a phosphorylation assay demonstrated that PKG directly phosphorylates TRPC1 at Ser172 and Thr313 in endothelial cells. In addition, PKG activator 8-Br-cGMP markedly reduced the magnitude of the 4αPDD-induced and 11,12-EET-induced [Ca(2+)]i transients, the cation current and vascular relaxation.
Conclusion: This study uncovers a novel mechanism by which PKG negatively regulates endothelial heteromeric TRPV4-C1 channels through increasing the spatial proximity of TRPV4-C1 to PKG1α via translocation and through phosphorylating Ser172 and Thr313 of TRPC1.