High-speed fluorescence microscopy of cell signaling

A high-speed fluorescence microscope was constructed to observe the spatio-temporal dynamics of chemical signals within living cells. Typically, the CCD is gated for < 1 microsec. with an similar to 2 msec. duty cycle to create "stop-action" movies of cells. The fluorescence of endogenous substances and/or exogenous labels was observed. We found that chemical signals travel as waves within cells. These include waves of Ca2+, pH, membrane depolarization and metabolites, which were missed in previous studies because they traverse a cell (d similar to 10 mu m) in a time that is much shorter than a typical camera's shutter speed. Not only are these dynamic chemical structures present in cells, but the initiation points, speeds, locations, and shapes vary. These waves underlie cellular processes such as chemotactic orientation, phagolysosome fusion, phagocytosis, transmembrane signaling, adherence, oxidant production, cell migration, and tumor cell killing. Studies of cell-cell interactions show that immune cells are capable of synchronizing their signaling apparatuses, thus cooperating to mediate target cell destruction., By combining high-speed imaging with conventional biological methods, we have identified novel sites for drug discovery based upon perturbations of chemical waves within cells. We propose that chemical waves in cells travel well-defined pathways at specific times to mediate information transduction, processing and distribution - much like a computer chip.