The incidence of hypertension, stroke and coronary artery disease increases dramatically in patients with non- insulin dependent type 2 diabetes. Aberrant Ca2+ influx via L-type CaV1.2 channels (LTCCs) leading to enhanced vascular smooth muscle (VSM) contraction, myogenic tone and blood flow/pressure has been implicated in the chain of events contributing to hyperglycemia (HG)-induced vascular complications during diabetes. Yet, the mechanisms involved in this pathological alteration are unclear. We recently discovered exciting new data indicating that anchoring of protein kinase A (PKA) by the scaffolding protein AKAP150 (AKAP79 is the human ortholog) is required for stimulation of LTCC activity and vasoconstriction during HG and diabetes. This contrasts the conventional notion that increases in cAMP/PKA activity leads to VSM relaxation and vasodilation. Thus, the overall goal of this competitive renewal application is to address two fundamental gaps in knowledge raised by our novel observations: 1) could spatial confinement of sarcolemmal cAMP/PKA signals in VSM during HG promote vasoconstriction? and 2) what upstream mechanisms trigger cAMP/PKA signaling during HG/diabetes? Preliminary data indicate that spatially discrete and heterogeneous cAMP/PKA signaling foster LTCC potentiation and VSM contraction during HG/diabetes. We also provide compelling evidence implicating a novel AKAP150-anchored P2Y11 receptor (P2Y11), which is coupled to GS, as an essential component of PKA-mediated CaV1.2 phosphorylation, functional upregulation of channel activity, enhanced Ca2+ influx, activation of calcineurin (CaN)/NFATc3-dependent signaling and vasoconstriction in HG/diabetes. Compelling results reproducing these pathological changes in native human VSM/arteries from non-diabetic and diabetic patients underscore the translational significance of our data. Beyond an unexpected role for GS-coupled P2Y11 signaling in vascular physiology, the pathological induction of compartmentalized adenylyl cyclase (AC)/PKA signaling leading to VSM contraction during HG/diabetes is a highly innovative concept of our model.
Two aims will be investigated to test the central hypothesis that a macromolecular complex involving the P2Y11, AKAP150, AC and PKA underlies CaV1.2 phosphorylation and LTCC-mediated Ca2+ influx in response to HG/diabetes.
Aim 1 will examine the hypothesis that spatially confined AC/PKA signaling stimulates LTCCs to trigger PKA-mediated VSM contraction and vasoconstriction during HG/diabetes.
Aim 2 will investigate the hypothesis that an AKAP150-anchored P2Y11 complex mediates compartmentalized AC/PKA activity, LTCC upregulation and vasoconstriction during HG/diabetes. Methods used to test these hypotheses will include optical techniques developed by our group, super-resolution microscopy, optogenetics, genetically encoded biosensors, state-of-the-art electrophysiology, molecular biology, telemetry and blood flow measurements. Experiments proposed in this transformative/translational study will provide invaluable mechanistic information that could lay the foundation for novel early intervention therapeutic strategies during diabetic vascular dysfunction.
Cardiovascular complications in the USA have reached pandemic proportions fueled in part by rising obesity rates and diabetes. Vascular complications associated with diabetes contribute to hypertension, heart disease and stroke. Here we will carry out careful quantitative studies to understand the role of a novel AKAP-anchored purinergic signal that stimulates PKA-mediated vasoconstriction during diabetes. The results from the proposed work could inform novel therapeutic strategies for early intervention in the treatment of diabetic hypertension.
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