Abstract . How a given protein organizes into a functional complex in health and disease is particularly relevant for membrane proteins that serve as key information entry points for cells. A suitable and highly relevant example is voltage-gated L-type CaV1.2 channels, which play a major role in arterial myocyte function and vascular reactivity. These channels have been shown to gate in unison (i.e. cooperative gating) to amplify Ca2+ influx. At present, however, a comprehensive understanding of mechanisms fostering the induction of CaV1.2 cooperative gating as well as its functional implications in health and disease represent major knowledge gaps. The overall objective of this proposal is to investigate the requirement and physiological consequences whereby phosphorylation of a single amino acid – S1928 – in the C-terminal of vascular CaV1.2 channels promotes dynamic spatial organization of CaV1.2 to facilitate cooperative gating at the surface membrane. To accomplish this goal, we are testing the central hypothesis that CaV1.2 S1928 phosphorylation tunes dynamic channel clustering and cooperative gating, and that this contributes to modulate vascular function in response to elevated extracellular glucose and during diabetes. This hypothesis is formulated on the basis of strong and rigorous preliminary data revealing an unanticipated and remarkable role for S1928 phosphorylation as the culprit for redistribution and assembly of CaV1.2 subunits into superclusters at the surface membrane of arterial myocytes upon elevated glucose and diabetes. CaV1.2 superclusters mediated by S1928 phosphorylation promotes CaV1.2 cooperative gating and Ca2+ influx amplification into arterial myocytes. Key findings that further underscore the significance of our observations is that CaV1.2 S1928 phosphorylation is necessary for activation of prohypertensive signaling pathways, vasoconstriction and altered blood flow upon elevated glucose and during diabetes. Moreover, critical observations have been validated in freshly dissociated human arterial myocytes from nondiabetic and diabetic patients, underscoring the translational relevance. Emerging and innovative concepts that will be explored in this application are the role of S1928 phosphorylation as 1) a rheostat of CaV1.2 function and vascular reactivity and 2) a major risk factor for vascular complications in diabetes. A multiscale contemporary approach that includes innovative microscopy techniques, sophisticated biochemistry, electrophysiology, in silico analysis and unique animal models will be implemented to explore the following aims. Aim 1 is to elucidate the role of S1928 phosphorylation in dynamic CaV1.2 clustering and cooperative gating upon elevated glucose. Aim 2 is to examine the requirement of S1928 phosphorylation to induce CaV1.2 superclustering and cooperative gating in arterial myocytes during diabetes. Results will transform our understanding of how CaV1.2 are organized in arterial myocytes (an...