GABA-A receptor plasticity: regulation by hypoxia

描述（由申请人提供）：我们的长期目标是了解GABAA受体（一种五聚体配体门控离子通道）的可塑性如何参与维持CNS功能。拟议的研究将测试的假设，两个GABAA受体亚基的表达变化，？6、？4、参与介导对缺氧的反应。在以往的研究中，我们发现，持续低压缺氧选择性触发新生？6亚基mRNA和蛋白质的表达和增加？4、？亚基mRNA水平在脑桥，脑干区域参与维持稳态。诱导？6的表达是值得注意的，因为该亚基通常仅在出生后的小脑中发现。更重要的是，？6或？4、在其他脑区，与？在介导对基础水平GABA的应答的突触外GABAA受体中，即，紧张性抑制探讨GABAA受体可塑性在持续缺氧反应中的作用，对野生型和？6或？4亚单位缺陷小鼠提出：1）确定如何持续低压缺氧改变GABAA受体亚单位mRNA表达的小鼠脑干保持在控制或缺氧条件下使用qRT-PCR; 2）定位细胞表达？6、？4亚基多肽，并确定是否在亚基水平的变化改变受体数量在脑干持续缺氧后，使用免疫组化和生物化学方法;和3）确定的重要性？4或？图6使用全身体积描记术的GABAA受体亚单位表达对持续缺氧的缓解反应。这些研究的结果将开始确定用于适应缺氧的分子机制，缺氧是一种在高海拔和包括慢性阻塞性肺病在内的几种病理条件下发生的生理压力。具体而言，拟议的研究将提供深入了解GABAA受体可塑性的贡献。我们的发现将为旨在了解维持大脑功能的回路的研究奠定基础。确定参与对持续缺氧反应的分子机制是创造新的治疗方法以对抗各种可能危及生命的疾病的重要第一步。 成熟的大脑适应环境压力的能力是生存所必需的。我们最近的研究结果提高了GABAA受体的可塑性的可能性，它介导的行动，在大脑中的主要抑制性神经递质，参与介导适应缺氧。缺氧是一种压力，发生在许多生理和病理条件，包括生活在高海拔和慢性阻塞性肺病。我们提出的研究的目标是证明特定GABAA受体亚基表达的变化是适应缺氧所必需的。确定参与对缺氧反应的分子机制是创造新的治疗方法以对抗各种可能危及生命的情况的重要第一步。

DESCRIPTION (provided by applicant): Our long term goal is to understand how plasticity of the GABAA receptor, a pentameric ligand-gated ion channel, participates in maintaining CNS function. The proposed studies will test the hypothesis that changes in expression of two GABAA receptor subunits, ?6 and ?4, participate in mediating the response to reduced oxygen. In previous studies on adult rats we found that sustained hypobaric hypoxia selectively triggers de novo ?6 subunit mRNA and protein expression and increases ?4 and ? subunit mRNA levels in the pons, a brainstem region involved in maintaining homeostasis. Induction of ?6 expression is notable because this subunit normally is found only in the postnatal cerebellum. More importantly, ?6 or ?4, in other brain regions, coassemble with ? in extrasynaptic GABAA receptors that mediate the response to basal levels of GABA, i.e., tonic inhibition. To investigate the role of GABAA receptor plasticity in the response to sustained hypoxia, molecular, histological, and physiologic studies on wild-type and ?6 or ?4 subunit-deficient mice are proposed to: 1) Determine how sustained hypobaric hypoxia alters GABAA receptor subunit mRNA expression in the brainstem of mice maintained in control or hypoxic conditions using qRT-PCR; 2) Locate cells that express the ?6 and ?4 subunit polypeptides and determine whether changes in subunit levels alter receptor number in the brainstem following sustained hypoxia using immunohistochemical and biochemical approaches; and 3) Determine the importance of ?4 or ?6 GABAA receptor subunit expression for the ventilatory response to sustained hypoxia using whole-body plethysmography. Findings from these studies will begin to define molecular mechanisms used in adapting to reduced oxygen, a stress that occurs physiologically at high altitude and in several pathological conditions, including chronic obstructive pulmonary diseases. Specifically, the proposed studies will provide insight into the contribution of GABAA receptor plasticity. Our findings will lay the groundwork for studies aimed at understanding the circuitry involved in maintaining brain function. Identifying the molecular machinery involved in the response to sustained hypoxia is an essential first step for creating novel therapeutic approaches to combat a variety of potentially life-threatening conditions. PUBLIC HEALTH RELEVANCE The ability of the mature brain to adapt to environmental stress is required for survival. Our recent findings raise the possibility that plasticity of the GABAA receptor, which mediates the actions of the major inhibitory neurotransmitter in the brain, participates in mediating adaptation to hypoxia. Oxygen deprivation is a stress that occurs during many physiological and pathological conditions, including life at high altitude and chronic obstructive pulmonary diseases. The goal of our proposed studies is to demonstrate that changes in the expression of specific GABAA receptor subunits are required for adaptation to hypoxia. Identifying the molecular machinery involved in the response to hypoxia is an essential first step for creating novel therapeutic approaches to combat a variety of potentially life-threatening situations.