Evolution of Calcium Channel Diversity

电压门控钙通道是在许多类型细胞的膜中发现的复杂蛋白质，对许多细胞的功能至关重要。在结构上，它们通常由形成孔隙的α 1亚基和相关的β、γ和α 2/ δ亚基组成。哺乳动物中至少有7个α - 1亚基和6个β亚基，因此钙通道家族在结构和功能上存在着巨大的多样性。该项目将确定高等动物钙通道的结构多样性是否在进化意义上被选择，以实现钙通道的许多不同功能，或者更确切地说，是基因复制和随后的组织特异性或发育性基因分离的“偶然”结果。假设是，在刺胞动物（水母及其近亲）中，最早存在神经系统的动物，钙通道类型很少，但它们可以满足功能齐全的神经系统的需要。如果这一假设是正确的，那么它将证明，钙通道之间的巨大结构多样性并不是神经肌肉系统功能所必需的。本提案的目的1是利用传统的分子克隆技术鉴定水母蓝藻中所有钙通道亚基。目的2是利用免疫组织化学绘制这些亚基在动物生命周期所有阶段的分布，并确定亚基共定位的任何模式。目标#3是在爪蟾的卵母细胞（发育中的卵）中表达克隆的亚基，以及先前克隆的形成孔的alpha1亚基，并表征在目标#2中鉴定的各种亚基组装产生的钙电流类型。本研究将为钙离子通道的演化提供基础信息。

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.