Fig. 1.

Spectral selectivity allows subcellular control over signaling while responses are imaged globally. In this diagrammatic representation, a migratory cell expressing inactive receptors (black) that are sensitive to 445 nm light is activated with a light beam on one side (blue box) resulting in asymmetric activation of the receptors (red). The cell shows a polarized response by extending lamellipodia in the direction of the optical signal. The cell also expresses a fluorescent protein (FP) sensor that is excited at 595 nm and emits at 620 nm indicating the concentration of a second messenger at the extending lamellipodia (pale orange diffuse distribution on the left and dark orange concentrated at the cellular extension on the right). The spectral tuning of a receptor to 445 nm prevents its activation during global imaging using 595 nm light and facilitates visualization response of the cell to subcellular optical activation of signaling.