Can we see PIP ₃ and hydrogen peroxide with a single probe?

A genetically encoded sensor for parallel measurements of phosphatidylinositol 3-kinase activity and hydrogen peroxide (H ₂O ₂) levels (termed PIP-SHOW) was developed. Upon elevation of local phosphatidylinositol 3,4,5-trisphosphate (PIP ₃) concentration, the sensor translocates from the cytosol to the plasma membrane, while a ratiometric excitation change rapidly and simultaneously reports changes in the concentration of H ₂O ₂. The dynamics of PIP ₃ and H ₂O ₂ generation were monitored in platelet-derived growth factor-stimulated fibroblasts and in T-lymphocytes after formation of an immunological synapse. We suggest that PIP-SHOW can serve as a prototype for many fluorescent sensors with combined readouts.