Brain insulin receptor causes activity-dependent current suppression in the olfactory bulb through multiple phosphorylation of Kv1.3
Brain insulin receptor causes activity-dependent current suppression in the olfactory bulb through multiple phosphorylation of Kv1.3
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DOI：
10.1152/jn.2000.83.4.2332
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发表时间：
2000-04-01
影响因子：
2.5
通讯作者：
Simmen, JA
中科院分区：
文献类型：
--
作者：
Fadool, DA;Tucker, K;Simmen, JA
胰岛素和胰岛素受体（IR）激酶在离散的脑区域中大量存在，但CNS中的胰岛素信号传导尚不清楚。因为它是已知的，最高的脑胰岛素结合亲和力，胰岛素受体密度，和IR激酶活性定位于嗅球，我们试图探索在大脑的这个区域的IR激酶的下游底物，以更好地阐明胰岛素信号在中枢神经系统中的功能。首先，我们证明了IR是出生后和发育中表达的高度可塑性嗅球（OB）的特定层。ELISA检测证实胰岛素存在于发育和成人OB中。血浆胰岛素水平高于OB中发现的水平，这可能表明存在差异性胰岛素库。然而，嗅球胰岛素水平似乎不是静态的，而是在禁食72小时后升高15倍。通过传统的全细胞和单通道膜片钳记录技术研究了胰岛素对培养的OB神经元的急性应用诱导外向电流抑制。OB神经元的调节仅限于电流大小; IR激酶激活不调节失活或失活的电流动力学。瞬时转染人胚肾细胞克隆Kv1.3离子通道，其中携带这些神经元中的外向电流的大部分，揭示了电流抑制的Kv1.3通道的多个酪氨酸磷酸化的结果。通道中Y到F的单点突变或IR中激酶结构域的缺失阻断了胰岛素诱导的Kv1.3的调节和磷酸化。OB神经元的Kv1.3电流的神经调节是活动依赖性的，并且在出生后第1天单侧鼻孔阻塞诱导的气味/感觉剥夺20天后被消除。IR激酶，但不是Kv1.3表达下调OB同侧闭塞，证明在冷冻切片的右（对照）和左（感官剥夺）OB免疫标记抗体针对这些蛋白质，分别。总的来说，这些数据支持这样的假设，即激素胰岛素在大脑中充当多功能分子：CNS中的IR信号传导可以在发育期间充当传统的生长因子，在能量代谢期间被改变，并且同时通过电压门控离子通道的磷酸化来调节电活动。
Insulin and insulin receptor (IR) kinase are found in abundance in discrete brain regions yet insulin signaling in the CNS is not understood. Because it is known that the highest brain insulin-binding affinities, insulin-receptor density, and IR kinase activity are localized to the olfactory bulb, we sought to explore the downstream substrates for IR kinase in this region of the brain to better elucidate the function of insulin signaling in the CNS. First, we demonstrate that IR is postnatally and developmentally expressed in specific lamina of the highly plastic olfactory bulb (OB). ELISA testing confirms that insulin is present in the developing and adult OB. Plasma insulin levels are elevated above that found in the OB, which perhaps suggests a differential insulin pool. Olfactory bulb insulin levels appear not to be static, however, but are elevated as much as 15-fold after a 72-h fasting period. Bath application of insulin to cultured OB neurons acutely induces outward current suppression as studied by the use of traditional whole-cell and single-channel patch-clamp recording techniques. Modulation of OB neurons is restricted to current magnitude; IR kinase activation does not modulate current kinetics of inactivation or deactivation. Transient transfection of human embryonic kidney cells with cloned Kv1.3 ion channel, which carries a large proportion of the outward current in these neurons, revealed that current suppression was the result of multiple tyrosine phosphorylation of Kv1.3 channel. Y to F single-point mutations in the channel or deletion of the kinase domain in IR blocks insulin-induced modulation and phosphorylation of Kv1.3. Neuromodulation of Kv1.3 current in OB neurons is activity dependent and is eliminated after 20 days of odor/sensory deprivation induced by unilateral naris occlusion at postnatal day 1. IR kinase but not Kv1.3 expression is downregulated in the OB ipsilateral to the occlusion, as demonstrated in cryosections of right (control) and left (sensory-deprived) OB immunolabeled with antibodies directed against these proteins, respectively. Collectively, these data support the hypothesis that the hormone insulin acts as a multiply functioning molecule in the brain: IR signaling in the CNS could act as a traditional growth factor during development, be altered during energy metabolism, and simultaneously function to modulate electrical activity via phosphorylation of voltage-gated ion channels.