Decoding Ca²⁺ signals : a question of timing

Receptor-stimulated Ca²⁺ signals come in several flavors. The Ca²⁺ signals can be decoded linearly or by integration of the response. How the duration of the signal conveyed by cytosolic Ca²⁺ concentration ([Ca²⁺]_i) changes is regulated is not well understood. Liu et al. (Liu, Q., S.A. Walker, D. Gao, J.A. Taylor, Y.-F. Dai, R.S. Arkell, M.D. Bootman, H.L. Roderick, P.J. Cullen, and P.J. Lockyer. 2005. J. Cell Biol. 170:183–190) now report an example of decoding based on the differential regulation of Ras function by two Ca²⁺-sensitive Ras inhibitors: Ca²⁺-promoted Ras activator (CAPRI), which extends the duration of the effect of Ca²⁺ on Ras activity, and Ras GTPase activating-like protein (RASAL), which functions as a linear decoder of the Ca²⁺ signal.