INFORMATION PROCESSING BY CALCIUM-ACTIVATED K+ CHANNELS

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Ion channels underlie all electrical signaling in the nervous system and so are the fundamental computational units of neural information processing. To understand learning and memory at the cellular and molecular level, the complex molecular networks that converge to modulate ion channels must be elucidated. In this study, the Ca2+-activated potassium (KCa) channel will be used as a model system to examine how the gating of ion channels is modified by the combinatorial action of multiple protein kinases, Ca2+, and voltage. KCa channels are of special relevance to mechanisms of plasticity as they provide a link between a neurons internal Ca2+ concentration and its membrane voltage. The amino acid sequences of cloned KCa channels reveal a rich potential for complex regulation; there are multiple consensus sites for ATP and at least five different types of protein kinase. The three specific aims that will be pursued using Drosophila and human KCa channels expressed in mammalian cell lines and Xenopus oocytes are: 1) to characterize the channel's voltage- and calcium-dependence 2) to identify the effects of individual protein kinases on channel gating and 3) to describe the interaction of multiple protein kinases acting on a single channel. A panel of five kinases will be applied to the channel individually and in various combinations and the resultant patterns of gating kinetics will be characterized using patch-clamp recording. Thus, while a single protein kinase may have a particular effect on the channel, new gating properties may emerge from the combinatorial action of multiple kinases. In addition, the order, number, and position of phosphate groups transferred by the kinases may have specific effects on channel gating. In this way, a single channel molecule could integrate and even store metabolic information.