A metabolic reaction–diffusion model for PKCα translocation via PIP₂ hydrolysis in an endothelial cell

Hydrolysis of the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP₂) at the cell membrane induces the release of inositol 1,4,5-trisphosphate (IP₃) into the cytoplasm and diffusion of diacylglycerol (DAG) through the membrane, respectively. Release of IP₃ subsequently increases Ca²⁺ levels in the cytoplasm, which results in activation of protein kinase C α (PKCα) by Ca²⁺ and DAG, and finally the translocation of PKCα from the cytoplasm to the membrane. In this study, we developed a metabolic reaction–diffusion framework to simulate PKCα translocation via PIP₂ hydrolysis in an endothelial cell. A three-dimensional cell model, divided into membrane and cytoplasm domains, was reconstructed from confocal microscopy images. The associated metabolic reactions were divided into their corresponding domain; PIP₂ hydrolysis at the membrane domain resulted in DAG diffusion at the membrane domain and IP₃ release into the cytoplasm domain. In the cytoplasm domain, Ca²⁺ was released from the endoplasmic reticulum, and IP₃, Ca²⁺, and PKCα diffused through the cytoplasm. PKCα bound Ca²⁺ at, and diffused through, the cytoplasm, and was finally activated by binding with DAG at the membrane. Using our model, we analyzed IP₃ and DAG dynamics, Ca²⁺ waves, and PKCα translocation in response to a microscopic stimulus. We found a qualitative agreement between our simulation results and our experimental results obtained by live-cell imaging. Interestingly, our results suggest that PKCα translocation is dominated by DAG dynamics. This three-dimensional reaction–diffusion mathematical framework could be used to investigate the link between PKCα activation in a cell and cell function.