1 Department of Anatomy and Neurobiology, 72054 Virginia Commonwealth University , Richmond, VA, USA.
2 Neuroscience Curriculum, 72054 Virginia Commonwealth University , Richmond, VA, USA.
ASN Neuro. 2017 Nov-Dec;9(6):1759091417745426. doi: 10.1177/1759091417745426.
The axon initial segment (AIS), the domain responsible for action potential initiation and maintenance of neuronal polarity, is targeted for disruption in a variety of central nervous system pathological insults. Previous work in our laboratory implicates oxidative stress as a potential mediator of structural AIS alterations in two separate mouse models of central nervous system inflammation, as these effects were attenuated following reactive oxygen species scavenging and NADPH oxidase-2 ablation. While these studies suggest a role for oxidative stress in modulation of the AIS, the direct effects of reactive oxygen and nitrogen species (ROS/RNS) on the stability of this domain remain unclear. Here, we demonstrate that oxidative stress, as induced through treatment with 3-morpholinosydnonimine (SIN-1), a spontaneous ROS/RNS generator, drives a reversible loss of AIS protein clustering in primary cortical neurons in vitro. Pharmacological inhibition of both voltage-dependent and intracellular calcium (Ca) channels suggests that this mechanism of AIS disruption involves Ca entry specifically through L-type voltage-dependent Ca channels and its release from IP-gated intracellular stores. Furthermore, ROS/RNS-induced AIS disruption is dependent upon activation of calpain, a Ca-activated protease previously shown to drive AIS modulation. Overall, we demonstrate for the first time that oxidative stress, as induced through exogenously applied ROS/RNS, is capable of driving structural alterations in the AIS complex.
轴突起始段（AIS）是负责动作电位起始和神经元极性维持的区域，在各种中枢神经系统病理损伤中都受到干扰。我们实验室的先前工作表明，氧化应激可能是中枢神经系统炎症的两种独立小鼠模型中 AIS 结构改变的潜在介质，因为这些影响在活性氧物质清除和 NADPH 氧化酶-2 消融后减弱。虽然这些研究表明氧化应激在调节 AIS 方面具有作用，但活性氧和氮物质（ROS/RNS）对该区域稳定性的直接影响仍不清楚。在这里，我们证明了通过使用 3-吗啉代丙基脒基丙基脒（SIN-1）处理诱导的氧化应激，一种自发的 ROS/RNS 生成剂，会导致体外原代皮质神经元中 AIS 蛋白聚集的可逆丧失。电压依赖性和细胞内钙（Ca）通道的药理学抑制表明，这种 AIS 破坏机制涉及 Ca 通过 L 型电压依赖性 Ca 通道进入，以及其从 IP 门控细胞内储存库中释放。此外，ROS/RNS 诱导的 AIS 破坏依赖于钙蛋白酶的激活，钙蛋白酶是一种先前被证明可驱动 AIS 调节的 Ca 激活蛋白酶。总体而言，我们首次证明了通过外源性应用 ROS/RNS 诱导的氧化应激能够驱动 AIS 复合物的结构改变。
