Dose-Dependent Responses to Calcium

Dynamic changes in signaling mechanisms may encode specific information critical to cellular regulation. Deciphering these messages requires sophisticated measurements of key signaling molecules in living cells. Teruel and Meyer present a method that allows measurement of calcium-dependent translocation of fluorescently tagged protein kinase Cγ (PKCγ) to the cell membrane in many single, living rat basophilic leukemia cells grown on glass microscope slides. The enzyme showed two distinct modes of response. When calcium was released from internal stores, there was transient movement of PKCγ to the cell surface for only a few seconds. However, signals that caused entry of extracellular calcium caused a persistent translocation of the enzyme to the cell surface that lasted for more than half a minute. Cells showed primarily the former response to low doses of platelet activation factor, and the latter response to larger doses. The results help explain how a common messenger like calcium can control discrete cellular responses. M. N. Teruel, T. Meyer, Parallel single-cell monitoring of receptor-triggered membrane translocation of a calcium-sensing protein module. Science 295, 1910-1912 (2002). [Abstract] [Full Text]