Biological And Biochemical Characterization Of Sigma Rec

该项目描述了Sigma-1受体(Sig-1R)的生化和药理学特性。SIG-1R是位于内质网(ER)的一种跨膜蛋白，与神经类固醇和某些抗抑郁药结合。抗抑郁药通过脑源性神经营养因子(BDNF)发挥作用，但确切的分子机制尚不清楚。脑源性神经营养因子可通过磷脂酶-γ(PLC-γ)/肌醇1，4，5-三磷酸(IP3)/钙离子途径增强培养的皮质神经元兴奋性谷氨酸能传递。因此，我们首先研究了抗抑郁药对BDNF信号转导途径的可能影响。此外，由于我们发现PLC-γ/IP3/Ca~(2+)通路受SIG-1R的调节，因此我们研究了抗抑郁药刺激的BDNF信号是否受SIG-1R的调节。我们发现，丙咪嗪或氟伏沙明可增强BDNF刺激的PLC-γ激活和随之而来的细胞内钙离子([Ca+]i)的升高，BDNF诱导的谷氨酸释放也增强。此外，丙咪嗪预处理后，PLC-γ与TrkB(脑源性神经营养因子受体)的相互作用增强。有趣的是，BD1047，一个强大的SIG-1R拮抗剂，阻断了丙咪嗪对BDNF诱导的PLC-γ激活和谷氨酸释放的依赖增强。相反，过度表达Sig-1R本身，在没有抗抑郁药预处理的情况下，增强了BDNF诱导的PLC-伽马激活和谷氨酸释放。这些结果表明，抗抑郁药预处理通过Sig-1R选择性地增强PLC-Gamma/IP3/Ca~(2+)通路上的BDNF信号，并且Sig-1R在BDNF信号转导导致谷氨酸释放中起重要作用。因此，我们的研究结果提示，抗抑郁药物可能通过增强SIG-1R的过度表达来增强BDNF信号，从而发挥其临床作用。

This project delineates biochemical and pharmacological properties of sigma-1 receptors (Sig-1R). Sig-1R are one-transmembrane proteins at the endoplasmic reticulum (ER) that bind neurosteroids and certain antidepressants. Antidepressants have been known to exert their actions via brain-derived neurotrophic factor (BDNF) but the exact molecular mechanism remains unknown. BDNF can reinforce excitatory glutamatergic transmission in cultured cortical neurons via the phospholipase-gamma (PLC-gamma)/inositol 1,4,5-trisphosphate (IP3)/Ca2+ pathway. Therefore, the possible effects of pretreatment with antidepressants on the BDNF signaling through the PLC-gamma)/IP3/Ca2+ pathway was examined first. Furthermore, because the PLC-gamma/IP3/Ca2+ pathway is shown by us to be regulated by Sig-1R, we examined whether the BDNF signaling stimulated by antidepressants is modulated by Sig-1R. We found that the BDNF-stimulated PLC-gamma activation and the ensued increase in intracellular Ca2+ ([Ca2+]i) were potentiated by pretreatment with imipramine or fluvoxamine, so was the BDNF-induced glutamate release. Furthermore, enhancement of the interaction between PLC-gamma and TrkB (receptor for BDNF) after imipramine pretreatment was observed. Interestingly, BD1047, a potent Sig-1R antagonist, blocked the imipramine-dependent potentiation on the BDNF-induced PLC-gamma activation and glutamate release. In contrast, overexpression of Sig-1R per se, without antidepressant pretreatment, enhances BDNF-induced PLC-gamma activation and glutamate release. These results suggest that antidepressant pretreatment selectively enhance the BDNF signaling on the PLC-gamma/IP3/Ca2+ pathway via Sig-1R, and that Sig-1R plays an important role in BDNF signaling leading to glutamate release. Thus, our results suggest that antidepressants may exert their clinical effects by potentiating BDNF signaling via the overexpression of Sig-1R.