FIGURE 10.

Proposed mechanistic model. Bold lines show direct interactions. Dashed lines show indirect interactions. Our work is consistent with the following simplified mechanistic model. Activation of PLCβ3 downstream of protease-activated receptor 1 (PAR-1) leads to the generation of diacylglycerol (DAG) and inositol 1,4,5-triphosphate (IP₃). IP₃ binds to and activates the endoplasmic reticulum (ER) IP₃ receptors (IP₃Rs), leading to Ca²⁺ release from the internal stores, a rise in cytosolic Ca²⁺ concentration ([Ca²⁺]_i), and the activation of the plasma membrane NCX. Concurrently, associated Na⁺-influx pathways that could be diacylglycerol-sensitive and/or plasma membrane depolarization (V_m) could lead to induction of reverse-mode NCX and Ca²⁺ influx. This Ca²⁺ influx promotes indirectly, via a yet unidentified Ca²⁺-sensitive mechanism, the assembly and subsequent activation of the NADPH oxidase 2 complex, resulting in ROS generation, ERK1/2 activation, and ultimately diminished endothelial barrier function and a pro-angiogenic phenotype. Ca²⁺ uptake via the sarcoendoplasmic reticulum Ca²⁺-ATPase (SERCA) could switch off the Ca²⁺ response. Other associated ionic mechanisms not depicted here for the sake of simplicity, such as mitochondrial Ca²⁺-uptake and/or store operated Ca²⁺ entry could further fine-tune indirectly the degree of NCX activation/reversal impacting on the functional output.