Lissin D V, Gomperts S N, Carroll R C, Christine C W, Kalman D, Kitamura M, Hardy S, Nicoll R A, Malenka R C, von Zastrow M
Department of Psychiatry, University of California, San Francisco, CA 94143, USA.
Proc Natl Acad Sci U S A. 1998 Jun 9;95(12):7097-102. doi: 10.1073/pnas.95.12.7097.
Distinct subtypes of glutamate receptors often are colocalized at individual excitatory synapses in the mammalian brain yet appear to subserve distinct functions. To address whether neuronal activity may differentially regulate the surface expression at synapses of two specific subtypes of ionotropic glutamate receptors we epitope-tagged an AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor subunit (GluR1) and an NMDA (N-methyl-D-aspartate) receptor subunit (NR1) on their extracellular termini and expressed these proteins in cultured hippocampal neurons using recombinant adenoviruses. Both receptor subtypes were appropriately targeted to the synaptic plasma membrane as defined by colocalization with the synaptic vesicle protein synaptophysin. Increasing activity in the network of cultured cells by prolonged blockade of inhibitory synapses with the gamma-aminobutyric acid type A receptor antagonist picrotoxin caused an activity-dependent and NMDA receptor-dependent decrease in surface expression of GluR1, but not NR1, at synapses. Consistent with this observation identical treatment of noninfected cultures decreased the contribution of endogenous AMPA receptors to synaptic currents relative to endogenous NMDA receptors. These results indicate that neuronal activity can differentially regulate the surface expression of AMPA and NMDA receptors at individual synapses.
在哺乳动物大脑中，不同亚型的谷氨酸受体常常共定位在单个兴奋性突触处，但似乎发挥着不同的功能。为了探究神经元活动是否可能以不同方式调节离子型谷氨酸受体的两种特定亚型在突触处的表面表达，我们在其细胞外末端对一个AMPA（α-氨基-3-羟基-5-甲基异恶唑-4-丙酸）受体亚基（GluR1）和一个NMDA（N-甲基-D-天冬氨酸）受体亚基（NR1）进行了表位标记，并使用重组腺病毒在培养的海马神经元中表达这些蛋白质。如通过与突触小泡蛋白突触素共定位所定义的，这两种受体亚型都被正确靶向到突触质膜。用A型γ-氨基丁酸受体拮抗剂印防己毒素长时间阻断抑制性突触，从而增加培养细胞网络中的活性，导致突触处GluR1而非NR1的表面表达出现活性依赖性和NMDA受体依赖性降低。与这一观察结果一致，对未感染培养物进行相同处理会使内源性AMPA受体对突触电流的贡献相对于内源性NMDA受体减少。这些结果表明，神经元活动可以以不同方式调节单个突触处AMPA和NMDA受体的表面表达。
