Inda Maria Carmen, DeFelipe Javier, Muñoz Alberto
Departamento de Biología Celular, Universidad Complutense de Madrid, Jose Antonio Novais 2, 28040 Madrid, Spain.
Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2920-5. doi: 10.1073/pnas.0511197103. Epub 2006 Feb 10.
The axon initial segment (AIS) of pyramidal cells is a critical region for the generation of action potentials and for the control of pyramidal cell activity. Here we show that Na+ and K+ voltage-gated channels, together with other molecules involved in the localization of ion channels, are distributed asymmetrically in the AIS of pyramidal cells situated in the human temporal neocortex. There is a high density of Na+ channels distributed along the length of the AIS together with the associated proteins spectrin betaIV and ankyrin G. In contrast, Kv1.2 channels are associated with the adhesion molecule Caspr2, and they are mostly localized to the distal region of the AIS. In general, the distal region of the AIS is targeted by the GABAergic axon terminals of chandelier cells, whereas the proximal region is innervated, mostly by other types of GABAergic interneurons. We suggest that this molecular segregation and the consequent regional specialization of the GABAergic input to the AIS of pyramidal cells may have important functional implications for the control of pyramidal cell activity.
锥体细胞的轴突起始段（AIS）是动作电位产生以及锥体细胞活动控制的关键区域。在此我们表明，钠和钾电压门控通道，连同其他参与离子通道定位的分子，在位于人类颞叶新皮质的锥体细胞的AIS中呈不对称分布。沿AIS长度分布着高密度的钠通道，以及相关蛋白血影蛋白βIV和锚蛋白G。相比之下，Kv1.2通道与粘附分子接触蛋白相关蛋白2（Caspr2）相关，且它们大多定位于AIS的远端区域。一般而言，AIS的远端区域是吊灯细胞的GABA能轴突终末的靶点，而近端区域主要由其他类型的GABA能中间神经元支配。我们认为，这种分子分隔以及由此导致的锥体细胞AIS的GABA能输入的区域特化可能对锥体细胞活动的控制具有重要的功能意义。
