Trafficking of the plasma membrane gamma-aminobutyric acid transporter GAT1. Size and rates of an acutely recycling pool.
Trafficking of the plasma membrane gamma-aminobutyric acid transporter GAT1. Size and rates of an acutely recycling pool.
复制标题
DOI：
10.1074/jbc.m500381200
复制
发表时间：
2005-03
期刊：
影响因子：
--
通讯作者：
Dan Wang;M. Quick
中科院分区：
文献类型：
--
作者：
Dan Wang;M. Quick
质膜神经递质转运体在神经元中快速往返于细胞表面。这种贩运可能在调节神经元信号传导方面很重要。这种管制将视贩运运输者的数目及其贩运率而定。在本研究中，我们在皮质神经元中定义了内源性γ -氨基丁酸转运体（GAT1）的急性循环池，其约占细胞总GAT1的三分之一。该池的动力学分析估计胞吐和内吞的时间常数分别为1.6和0.9分钟，因此大约三分之一的回收池是停留在基态的质膜。最近的证据表明GAT1底物、第二信使和相互作用蛋白调节GAT1的运输。这些触发器可以通过改变贩运率或改变回收池的大小来起作用。在本研究中，我们研究了三种GAT1调制器。钙耗竭通过减小循环池大小而降低GAT1表面表达。蔗糖通过阻断网格蛋白和动力蛋白依赖的内吞作用增加了GAT1表面的表达，但它不改变循环池的大小。蛋白激酶C通过增加胞吞率降低表面GAT1表达，但不改变胞吐率或循环池大小。根据皮质钮扣中GAT1分子的估计，目前的数据表明，大约有1000个转运蛋白组成急性再循环池，其中300个转运蛋白处于基础状态，每秒有5个转运蛋白插入质膜。这种插入可能代表了一个含有转运蛋白的囊泡的融合。
Plasma membrane neurotransmitter transporters rapidly traffic to and from the cell surface in neurons. This trafficking may be important in regulating neuronal signaling. Such regulation will be subject to the number of trafficking transporters and their trafficking rates. In the present study, we define an acutely recycling pool of endogenous gamma-aminobutyric acid transporters (GAT1) in cortical neurons that comprises approximately one-third of total cellular GAT1. Kinetic analysis of this pool estimates exocytosis and endocytosis time constants of 1.6 and 0.9 min, respectively, and thus approximately one-third of the recycling pool is plasma membrane resident in the basal state. Recent evidence shows that GAT1 substrates, second messengers, and interacting proteins regulate GAT1 trafficking. These triggers could act by altering trafficking rates or by changing the recycling pool size. In the present study we examine three GAT1 modulators. Calcium depletion decreases GAT1 surface expression by diminishing the recycling pool size. Sucrose increases GAT1 surface expression by blocking clathrin- and dynamin-dependent endocytosis, but it does not change the recycling pool size. Protein kinase C decreases surface GAT1 expression by increasing the endocytosis rate, but it does not change the exocytosis rate or the recycling pool size. Based upon estimates of GAT1 molecules in cortical boutons, the present data suggest that approximately 1000 transporters comprise the acutely recycling pool, of which 300 are on the surface in the basal state, and five transporters insert into the plasma membrane every second. This insertion could represent the fusion of one transporter-containing vesicle.