α1 S1928 Phosphorylation of Ca1.2 Channel Controls Vascular Reactivity and Blood Pressure.

BACKGROUND

Increased vascular Ca1.2 channel function causes enhanced arterial tone during hypertension. This is mediated by elevations in angiotensin II/protein kinase C signaling. Yet, the mechanisms underlying these changes are unclear. We hypothesize that α1 phosphorylation at serine 1928 (S1928) is a key event mediating increased Ca1.2 channel function and vascular reactivity during angiotensin II signaling and hypertension.

METHODS AND RESULTS

The hypothesis was examined in freshly isolated mesenteric arteries and arterial myocytes from control and angiotensin II-infused mice. Specific techniques include superresolution imaging, proximity ligation assay, patch-clamp electrophysiology, Ca imaging, pressure myography, laser speckle imaging, and blood pressure telemetry. Hierarchical "nested" and appropriate parametric or nonparametric test and ANOVAs were used to assess statistical differences. We found that angiotensin II redistributed the Ca1.2 pore-forming α1 subunit into larger clusters. This was correlated with elevated Ca1.2 channel activity and cooperativity, global intracellular Ca and contraction of arterial myocytes, enhanced myogenic tone, and altered blood flow in wild-type mice. These angiotensin II-induced changes were prevented/ameliorated in cells/arteries from S1928 mutated to alanine knockin mice, which contain a negative modulation of the α1 S1928 phosphorylation site. In angiotensin II-induced hypertension, increased α1 clustering, Ca1.2 activity and cooperativity, myogenic tone, and blood pressure in wild-type cells/tissue/mice were averted/reduced in S1928 mutated to alanine samples.

CONCLUSIONS

Results suggest an essential role for α1 S1928 phosphorylation in regulating channel distribution, activity and gating modality, and vascular function during angiotensin II signaling and hypertension. Phosphorylation of this single vascular α1 amino acid could be a risk factor for hypertension that may be targeted for therapeutic intervention.