Evolution of Calcium Channel Diversity

IBN 98-08386 Anderson电压门控钙通道是一种复杂的蛋白质，存在于许多类型的细胞膜上，对它们的许多功能至关重要。在结构上，它们通常由形成孔隙的α1亚单位以及相关的β、伽马和α2/三角洲亚单位组成。由于哺乳动物中至少有7种α1亚基和6种β亚基，因此钙通道家族中存在着巨大的结构和功能多样性。该项目将确定高等动物体内钙通道的结构多样性是否在进化意义上被选择来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基因分离的‘偶然’结果。假说是，在现存最早有神经系统的动物--蛇形动物(水母及其近亲)中，钙通道类型很少，但它们可以满足完全功能的神经系统的需要。如果这一假设是正确的，它将认为钙通道之间的巨大结构多样性不是发挥作用的神经肌肉系统所必需的。这项建议的第一个目的是使用常规的分子克隆技术来鉴定水母蓝藻中的所有钙通道亚基。目的#2是利用免疫组织化学技术绘制这些亚基在动物生命周期所有阶段的分布图，并确定这些亚基的任何共存模式。目的#3是在爪蛙卵母细胞(发育中的卵)中表达克隆的亚基和先前克隆的形成孔道的α1亚基，并表征在目的#2中确定的各种亚基组合产生的钙电流类型。

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.