Barbiero Valentina S, Giambelli Roberto, Musazzi Laura, Tiraboschi Ettore, Tardito Daniela, Perez Jorge, Drago Filippo, Racagni Giorgio, Popoli Maurizio
Department of Pharmacological Sciences and Center of Excellence on Neurodegenerative Diseases, Center of Neuropharmacology, University of Milano, Milano, Italy.
Neuropsychopharmacology. 2007 Dec;32(12):2511-9. doi: 10.1038/sj.npp.1301378. Epub 2007 Mar 14.
Changes in synaptic plasticity are involved in pathophysiology of depression and in the mechanism of antidepressants. Ca(2+)/calmodulin (CaM) kinase II, a protein kinase involved in synaptic plasticity, has been previously shown to be a target of antidepressants. We previously found that antidepressants activate the kinase in hippocampal neuronal cell bodies by increasing phosphorylation at Thr(286), reduce the kinase phosphorylation in synaptic membranes, and in turn its phosphorylation-dependent interaction with syntaxin-1 and the release of glutamate from hippocampal synaptosomes. Here, we investigated the chronic effect of different antidepressants (fluoxetine, desipramine, and reboxetine) on the expression and function of the kinase in distinct subcellular compartments in order to dissect the different kinase pools affected. Acute treatments did not induce any change in the kinase. In total tissue extracts chronic drug treatments induced activation of the kinase; in hippocampus (HC), but not in prefrontal/frontal cortex, this was partially accounted for by increased Thr(286) phosphorylation, suggesting the involvement of different mechanisms of activation. In synaptosomes, all drugs reduced the kinase phosphorylation, particularly in HC where, upon fractionation of the synaptosomal particulate into synaptic vesicles and membranes, we found that the drugs induced a redistribution and differential activation of the kinase between membranes and vesicles. Furthermore, a large decrease in the level and phosphorylation of synapsin I located at synaptic membranes was consistent with the observed decrease of CaM kinase II. Overall, antidepressants induce a complex pattern of modifications in distinct subcellular compartments; at presynaptic level, these changes are in line with a dampening of glutamate release.
突触可塑性的变化与抑郁症的病理生理学及抗抑郁药的作用机制有关。钙/钙调蛋白（CaM）激酶II是一种参与突触可塑性的蛋白激酶，先前已被证明是抗抑郁药的作用靶点。我们之前发现，抗抑郁药通过增加苏氨酸（Thr）286位点的磷酸化来激活海马神经元细胞体中的该激酶，降低突触膜中该激酶的磷酸化水平，进而减少其与 syntaxin-1的磷酸化依赖性相互作用以及海马突触体中谷氨酸的释放。在此，我们研究了不同抗抑郁药（氟西汀、地昔帕明和瑞波西汀）对不同亚细胞区室中该激酶表达和功能的慢性影响，以剖析受影响的不同激酶池。急性处理未引起该激酶的任何变化。在全组织提取物中，慢性药物处理可诱导该激酶的激活；在海马体（HC）中，但在前额叶/额叶皮质中未出现这种情况，这部分是由于Thr286磷酸化增加所致，提示涉及不同的激活机制。在突触体中，所有药物均降低了该激酶的磷酸化水平，尤其是在HC中，当将突触体颗粒分离为突触小泡和突触膜时，我们发现药物诱导了该激酶在膜和小泡之间的重新分布和差异激活。此外，位于突触膜上的突触素I的水平和磷酸化大幅降低与观察到的CaM激酶II的减少一致。总体而言，抗抑郁药在不同亚细胞区室中诱导出复杂的修饰模式；在突触前水平，这些变化与谷氨酸释放的减弱一致。
