IBN 98-08386 ANDERSON Voltage-gated calcium channels are complex proteins found in the membranes of many types of cell that are essential for many of their functions. Structurally, they usually consist of a pore- forming alpha1 subunit, and associated beta, gamma, and alpha2/delta subunits. Because there are at least 7 varieties of alpha1 subunit in mammals, and 6 beta subunits, there is enormous structural and functional diversity within the calcium channel family. The project will determine whether the structural diversity of calcium channels in higher animals has been selected, in the evolutionary sense, to fulfill the many different functions of calcium channels, or rather is an 'accidental' consequence of gene duplication and subsequent tissue-specific or developmental gene isolation. The hypothesis is that in cnidarians (jelly fish and their relatives), the earliest existing animals to have a nervous system, there are very few calcium channel types, but that they can meet the needs of a fully functional nervous system. If this hypothesis is correct, it would argue that enormous structural diversity among calcium channels is not required for a functioning neuromuscular system. Aim #1 of this proposal is to identify all calcium channel subunits in the jellyfish Cyanea using conventional molecular cloning techniques. Aim #2 is to map the distribution of those subunits in all stages of the animal's life cycle using immunohistochemistry, and to identify any patterns of co-localization of the subunits. Aim #3 is to express the cloned subunits in oocytes (developing eggs) from the clawed- frog Xenopus together with the previously cloned pore-forming alpha1 subunit and to characterize the types of calcium currents produced by the various subunit assemblies identified during Aim #2. The proposed research will provide fundamental information about the evolution of calcium channels.
