Department of Pharmacology and Toxicology, School of Pharmacy, University of Kansas, Lawrence, KS 66045, USA.
Int J Neuropsychopharmacol. 2009 Jun;12(5):651-65. doi: 10.1017/S1461145708009590. Epub 2008 Oct 31.
We have previously demonstrated that olanzapine-induced desensitization of 5-HT2A receptor-stimulated phospholipase C (PLC) activity is associated with increases in RGS7 protein levels both in vivo and in cells in culture, and the increase in RGS7 is dependent on activation of the JAK-STAT pathway in cells in culture. In the present study, we found that desensitization of 5-HT2A receptor-stimulated PLC activity induced by olanzapine is dependent on activation of the JAK-STAT pathway. Similar to olanzapine, clozapine-induced desensitization of 5-HT2A receptor signalling is accompanied by increases in RGS7 and activation of JAK2. Treatment with the selective 5-HT2A receptor antagonist MDL 100907 also increased RGS7 protein levels and JAK2 activation. Using a JAK2 inhibitor AG490, we found that clozapine and MDL 100907-induced increases in RGS7 are dependent on activation of the JAK-STAT pathway. Olanzapine, clozapine, and MDL 100907 treatment increased mRNA levels of RGS7. Using a chromatin immunoprecipitation assay we found STAT3 binding to the putative RGS7 promoter region. Taken together, olanzapine-induced activation of the JAK-STAT pathway, and STAT3 binding to the RGS7 gene could underlie the increase in RGS7 mRNA which could subsequently increase protein expression. Furthermore, the increase in RGS7 protein could play a role in the desensitization of 5-HT2A receptor signalling by terminating the activated Galphaq/11 proteins more rapidly. Overall, our data suggest that the complete desensitization of 5-HT2A receptor-stimulated PLC activity by olanzapine, clozapine and MDL 100907 requires activation of the JAK-STAT pathway, which in turn increases RGS7 expression probably by direct transcriptional activity of STAT3.
我们之前的研究表明，奥氮平诱导的 5-HT2A 受体刺激的 PLC 活性脱敏与体内和细胞培养中 RGS7 蛋白水平的增加有关，而细胞培养中 RGS7 的增加依赖于 JAK-STAT 途径的激活。在本研究中，我们发现奥氮平诱导的 5-HT2A 受体刺激的 PLC 活性脱敏依赖于 JAK-STAT 途径的激活。与奥氮平类似，氯氮平诱导的 5-HT2A 受体信号脱敏伴随着 RGS7 的增加和 JAK2 的激活。用选择性 5-HT2A 受体拮抗剂 MDL 100907 处理也增加了 RGS7 蛋白水平和 JAK2 的激活。用 JAK2 抑制剂 AG490 处理，我们发现氯氮平和 MDL 100907 诱导的 RGS7 增加依赖于 JAK-STAT 途径的激活。奥氮平、氯氮平和 MDL 100907 处理增加了 RGS7 的 mRNA 水平。用染色质免疫沉淀试验，我们发现 STAT3 结合到 RGS7 基因的假定启动子区域。综上所述，奥氮平诱导的 JAK-STAT 途径的激活以及 STAT3 结合到 RGS7 基因可能导致 RGS7 mRNA 的增加，从而增加蛋白质的表达。此外，RGS7 蛋白的增加可能通过更迅速地终止激活的 Galphaq/11 蛋白，在 5-HT2A 受体信号脱敏中发挥作用。总的来说，我们的数据表明，奥氮平、氯氮平和 MDL 100907 完全脱敏 5-HT2A 受体刺激的 PLC 活性需要 JAK-STAT 途径的激活，这反过来又通过 STAT3 的直接转录活性增加 RGS7 的表达。
