Picower Institute for Learning and Memory, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Neurosci. 2013 Jul 17;33(29):12122-35. doi: 10.1523/JNEUROSCI.0131-13.2013.
Activity of glycogen synthase kinase-3β (GSK-3β) is required for long-term depression (LTD) via molecular mechanisms that are incompletely understood. Here, we report that PSD-95, a major scaffold protein of the postsynaptic density (PSD) that promotes synaptic strength, is phosphorylated on threonine-19 (T19) by GSK-3β. In cultured rat hippocampal neurons, phosphorylation of T19 increases rapidly with chemical LTD and is attenuated by pharmacologic or genetic suppression of GSK-3β. In organotypic rat hippocampal slices, we find that a nonphosphorylatable PSD-95 mutant (T19A) tagged with photoactivatable green fluorescent protein (PAGFP) shows enhanced stability in dendritic spines versus wild-type PSD-95, whereas the phosphomimetic mutant (PSD-95-T19D) is more readily dispersed. Further, overexpression of PSD-95-T19A, but not WT-PSD-95, impairs AMPA receptor internalization and the induction of LTD. These data indicate that phosphorylation on T19 by GSK-3β destabilizes PSD-95 within the PSD and is a critical step for AMPA receptor mobilization and LTD.
糖原合酶激酶-3β（GSK-3β）的活性通过分子机制对于长时程抑制（LTD）是必需的，但这些机制尚不完全清楚。在这里，我们报告 PSD-95，即突触后密度（PSD）的主要支架蛋白，可促进突触强度，其第 19 位苏氨酸（T19）可被 GSK-3β磷酸化。在培养的大鼠海马神经元中，T19 的磷酸化作用随着化学 LTD 迅速增加，并可通过 GSK-3β 的药理学或遗传学抑制而减弱。在器官型大鼠海马切片中，我们发现，被光活化绿色荧光蛋白（PAGFP）标记的非磷酸化 PSD-95 突变体（T19A）与野生型 PSD-95 相比，在树突棘中显示出增强的稳定性，而磷酸模拟突变体（PSD-95-T19D）则更容易分散。此外，PSD-95-T19A 的过表达，而不是 WT-PSD-95，会损害 AMPA 受体内化和 LTD 的诱导。这些数据表明，GSK-3β 对 T19 的磷酸化作用使 PSD-95 在 PSD 内不稳定，并且是 AMPA 受体动员和 LTD 的关键步骤。
