González Marco I, Bannerman Peter G, Robinson Michael B
Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia 19104-4318, USA.
J Neurosci. 2003 Jul 2;23(13):5589-93. doi: 10.1523/JNEUROSCI.23-13-05589.2003.
Sodium-dependent transporters clear extracellular glutamate in the mammalian CNS. Activation of protein kinase C (PKC) rapidly increases the activity of the neuronal glutamate transporter EAAC1 (excitatory amino acid carrier-1). This effect is associated with redistribution of EAAC1 to the cell membrane and appears to be dependent on a particular PKC subtype, PKCalpha. In the present study, we sought to determine whether this specificity for regulation of EAAC1 is associated with the formation of EAAC1-PKCalpha complexes. In C6 glioma cells, activation of PKC with phorbol 12-myristate 13-acetate (PMA) induced formation of EAAC1-PKCalpha complexes but did not induce formation of complexes with PKCdelta, a PKC not thought to regulate EAAC1. Formation of these complexes was blocked by inhibitors of PKC. Confocal microscopy revealed that PMA caused EAAC1 and PKCalpha to colocalize in clusters at or near the cell surface. The EAAC1-PKCalpha complexes were also observed in rat brain synaptosomes, demonstrating that this interaction is not restricted to C6 cells. These data demonstrate that EAAC1 and PKCalpha interact in a PKC-dependent manner that is associated with EAAC1 redistribution. Although PKC activation has been implicated in the regulation of many different neurotransmitter transporters, this study provides the first example of an interaction between a neurotransmitter transporter and PKC. PKCalpha also forms complexes with GluR2 (glutamate receptor subunit 2) and causes a reduction in the levels of GluR2-containing AMPA receptors at the plasma membrane. Together, these data suggest that PKCalpha may simultaneously trigger the redistribution of EAAC1 and glutamate receptors.
钠依赖性转运体清除哺乳动物中枢神经系统中的细胞外谷氨酸。蛋白激酶C(PKC)的激活迅速增加神经元谷氨酸转运体EAAC1(兴奋性氨基酸载体1)的活性。这种效应与EAAC1向细胞膜的重新分布有关,并且似乎依赖于特定的PKC亚型PKCalpha。在本研究中,我们试图确定对EAAC1调节的这种特异性是否与EAAC1-PKCalpha复合物的形成有关。在C6胶质瘤细胞中,用佛波酯12-肉豆蔻酸酯13-乙酸酯(PMA)激活PKC诱导了EAAC1-PKCalpha复合物的形成,但未诱导与PKCdelta(一种不认为调节EAAC1的PKC)形成复合物。这些复合物的形成被PKC抑制剂阻断。共聚焦显微镜显示,PMA导致EAAC1和PKCalpha在细胞表面或其附近共定位成簇。在大鼠脑突触体中也观察到了EAAC1-PKCalpha复合物,表明这种相互作用不限于C6细胞。这些数据表明,EAAC1和PKCalpha以PKC依赖性方式相互作用,这与EAAC1的重新分布有关。虽然PKC激活与许多不同神经递质转运体的调节有关,但本研究提供了神经递质转运体与PKC之间相互作用的第一个例子。PKCalpha还与GluR2(谷氨酸受体亚基2)形成复合物,并导致质膜上含GluR2的AMPA受体水平降低。总之,这些数据表明PKCalpha可能同时触发EAAC1和谷氨酸受体的重新分布。