Adaptive evolution of voltage-gated sodium channels: The first 800 million years
Adaptive evolution of voltage-gated sodium channels: The first 800 million years
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DOI：
10.1073/pnas.1201884109
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发表时间：
2012-06-26
影响因子：
11.1
通讯作者：
Zakon, Harold H.
中科院分区：
文献类型：
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作者：
Zakon, Harold H.
电压门控Na+渗透（Nav）通道形成动物电兴奋性的基础。Nav通道是从Ca2+通道进化而来的，存在于领鞭毛虫和动物的共同祖先中，尽管该通道可能对Na+和Ca2+都是可渗透的。因此，像许多其他神经元通道和受体一样，Nav通道早于神经元。无脊椎动物拥有两个Nav通道（Nav1和Nav2），而脊椎动物的Nav通道属于Nav1家族。大约500 Mya在早期脊索动物的导航通道演变的基序，使他们能够集群在轴突的初始段，50万年后，随着髓鞘的演变，导航通道“资本化”这个属性和集群节点的Ranvier。传导速度的增强沿着颌骨的进化，可能使早期有颚类成为凶猛的捕食者，成为海洋中的优势脊椎动物。后来在脊椎动物进化中，Nav通道基因家族在四足动物和硬骨鱼类中平行扩展（类似于9至10个基因在脊椎动物中，8个基因在硬骨鱼类中）。这种扩张发生在泥盆纪晚期灭绝期间或之后，当时硬骨鱼和四足动物各自在各自的栖息地中多样化，并且与两组中端脑核数量的增加相吻合。Nav通道的扩展可能允许更复杂的神经计算和Nav通道动力学与钾通道动力学的定制以增强能量节省。导航通道显示出适应性序列进化，以增加通信信号（电鱼）的多样性，防止致命的导航通道毒素（蛇，蝾螈，河豚，昆虫），并在专门的栖息地（裸鼹鼠）。
Voltage-gated Na+-permeable (Nav) channels form the basis for electrical excitability in animals. Nav channels evolved from Ca2+ channels and were present in the common ancestor of choanoflagellates and animals, although this channel was likely permeable to both Na+ and Ca2+. Thus, like many other neuronal channels and receptors, Nav channels predated neurons. Invertebrates possess two Nav channels (Nav1 and Nav2), whereas vertebrate Nav channels are of the Nav1 family. Approximately 500 Mya in early chordates Nav channels evolved a motif that allowed them to cluster at axon initial segments, 50 million years later with the evolution of myelin, Nav channels "capitalized" on this property and clustered at nodes of Ranvier. The enhancement of conduction velocity along with the evolution of jaws likely made early gnathostomes fierce predators and the dominant vertebrates in the ocean. Later in vertebrate evolution, the Nav channel gene family expanded in parallel in tetrapods and teleosts (similar to 9 to 10 genes in amniotes, 8 in teleosts). This expansion occurred during or after the late Devonian extinction, when teleosts and tetrapods each diversified in their respective habitats, and coincided with an increase in the number of telencephalic nuclei in both groups. The expansion of Nav channels may have allowed for more sophisticated neural computation and tailoring of Nav channel kinetics with potassium channel kinetics to enhance energy savings. Nav channels show adaptive sequence evolution for increasing diversity in communication signals (electric fish), in protection against lethal Nav channel toxins (snakes, newts, pufferfish, insects), and in specialized habitats (naked mole rats).