RP4: Synaptic regulation of GABAA receptor turnover

GABAA受体（GABAAR）在神经元中经历广泛的内吞作用，随后再循环至表面膜或蛋白质降解。网格蛋白依赖的内吞作用似乎是启动受体内化的主要机制。网格蛋白接头蛋白2（clathrin-adaptor protein 2，AP 2）通过μ2亚基与GABAAR结合。PKA以及PKC依赖性磷酸化调节GABAAR的表面稳定性。不同的GABAAR结合蛋白参与调节内化受体的命运。例如，亨廷顿蛋白相关蛋白（HAP 1）与GABAAR β亚基结合，HAP 1过表达抑制GABAAR降解，从而增加受体再循环。类似地，Plic-1似乎调节受体周转并促进GABAAR在神经元表面membranes.In第一个FG 885资助期间的积累，我们的结果增加了一个新的球员控制突触GABAAR周转系统。泛素特异性蛋白酶Usp 14似乎调节携带单/寡泛素标记的含α1亚基的GABAAR。基因敲低Usp 14产生共济失调表型，表现为广泛的GABAAR重新分布到神经元表面。这些影响是可逆的，需要催化蛋白酶活性的Usp 14 enzymes.Recent数据从我们的实验室确定了两个肌动蛋白为基础的肌球蛋白马达蛋白，与铝亚基含有GABAARs。myoV的性质，代表一个顺行电机，以及性质myoVI逆行方向移动，表明这两个因素可能是驱动程序，介导GABAAR质膜和膜下囊泡室之间的重新分配。与AMPA型谷氨酸受体的周转类似，拟议的项目旨在研究GABAAR-肌球蛋白相互作用的机制。由于抑制性突触的性质，主要位于树突轴，而不是在区域限制的脊柱头舱，我们希望确定的主要机制，神经递质受体营业额不同于营业额机制兴奋性突触。

GABAA receptors (GABAARs) undergo extensive endocytosis in neurons followed by either recycling to the surface membrane or protein degradation. Clathrin-dependent endocytosis appears to be the major mechanism that initiates receptor internalization. The clathrin-adaptor protein 2 (AP2) associates with GABAARs via the μ2 subunit. PKA as well as PKC-dependent phosphorylation regulate the surface stability of GABAARs. Different GABAAR binding proteins participate in the regulation of internalized receptor fate. For instance, the Huntingtin-associated protein (HAP1) binds to GABAAR β subunits and HAP1 overexpression inhibits GABAAR degradation, thereby increasing receptor recycling. Similarly, Plic-1 appears to regulate receptor turnover and facilitates GABAAR accumulation at neuronal surface membranes.In the first FG885 funding period, our results added a new player to the system controlling synaptic GABAAR turnover. The ubiquitin-specific protease Usp14 appears to regulate α1 subunit-containing GABAARs that carry a mono-/oligo-ubiquitin label. Genetic knockdown of Usp14 generates an ataxia phenotype, represented by an extensive GABAAR redistribution to the neuron surface. These effects are reversible and require the catalytic protease activity of Usp14 enzymes.Recent data from our laboratory identified two actin-based myosin motor proteins that associate with al subunit-containing GABAARs. The nature of myoV, representing an anterograde motor, as well as the nature of myoVI moving in retrograde directions, suggests that both factors might be the drivers that mediate GABAAR redistribution between plasma membrane and submembrane vesicle compartments. In analogy to the turnover of AMPA-type glutamate receptors, the proposed project aims to study the mechanisms of GABAAR-myosin interactions. Due to the nature of inhibitory synapses that mainly locate at dendrite shafts, rather than at the regionally restricted spine head compartments, we expect to identify principal mechanisms of neurotransmitter receptor turnover that differ from turnover mechanisms at excitatory synapses.