Fluorescent biosensor imaging meets deterministic mathematical modelling: quantitative investigation of signalling compartmentalization

Cells execute specific responses to diverse environmental cues by encoding information in distinctly compartmentalized biochemical signalling reactions. Genetically encoded fluorescent biosensors enable the spatial and temporal monitoring of signalling events in live cells. Temporal and spatiotemporal computational models can be used to interpret biosensor experiments in complex biochemical networks and to explore hypotheses that are difficult to test experimentally. In this review, we first provide brief discussions of the experimental toolkit of fluorescent biosensors as well as computational basics with a focus on temporal and spatiotemporal deterministic models. We then describe how we used this combined approach to identify and investigate a protein kinase A (PKA) - cAMP - Ca2+ oscillatory circuit in MIN6 & beta; cells, a mouse pancreatic & beta; cell system. We describe the application of this combined approach to interrogate how this oscillatory circuit is differentially regulated in a nano-compartment formed at the plasma membrane by the scaffolding protein A kinase anchoring protein 79/150. We leveraged both temporal and spatiotemporal deterministic models to identify the key regulators of this oscillatory circuit, which we confirmed with further experiments. The powerful approach of combining live-cell biosensor imaging with quantitative modelling, as discussed here, should find widespread use in the investigation of spatiotemporal regulation of cell signalling.image Abstract figure legend Complex cross-regulation between cAMP, protein kinase A and calcium in & beta; cells leads to coordinated oscillatory behaviour, which can be measured in individual cells using genetically encoded fluorescent biosensors. Furthermore, subcellular targeting of genetically encoded fluorescent biosensors enables the detection of compartment-specific, coordinated oscillations of signalling components in cells. The underlying mechanisms behind the coordinated oscillations can be investigated using temporal (ordinary differential equation) and spatiotemporal (partial differential equation) computational models. This figure was made using Biorender.com.image

Automated summary

Cells respond to environmental cues by encoding information in compartmentalized biochemical signaling reactions. Genetically encoded fluorescent biosensors enable the monitoring of signaling events in live cells. Temporal and spatiotemporal computational models can be used to interpret biosensor experiments and explore hypotheses difficult to test experimentally.