自噬介导的杏仁核区AMPA受体内吞在恐惧消退中的作用及机制研究

Failure of fear extinction leads to anxiety-like psychiatric disorders, such as posttraumatic stress disorder, and drugs which could promote fear extinction may increase the response rate and efficiency of cognitive-behavioral therapy for anxiety-like disorders. It has been reported that the endocytosis of postsynaptic AMPARs and long-term depression (LTD) contributed to the fear extinction. Moreover, autophagy has been proved to play a key role in the endocytosis and degradation of postsynaptic AMPARs during chemical-LTD. In previous research, we found that autophagy in amygdala contributed to fear memory consolidation, furthermore, our preliminary experiments showed that the level of autophagy in amygdala was increased after fear extinction, and pharmacological inhibition of autophagy blocked the LTD of thalamic-lateral transmission and impaired the fear extinction. We then build the hypothesis that autophagy induced by fear extinction may selectively degrade the postsynaptic AMPARs, and thus enhance the LTD and promotes fear extinction. In the current project, we plan to investigate the role of autophagy in fear extinction model by combinations of molecular biological, genetic and behavioral tests, and demonstrate the regulation role of autophagy in the expression of AMPARs and synaptic plasticity using electeophysiological tools. To the end, this study will provide evidence for new strategy and potential drug targets for the treatment of anxiety-like psychiatric disorders.

恐惧记忆难以消退是焦虑类精神疾病的治疗难点，通过药物促进恐惧消退则能提高这类疾病的治疗应答率及疗效。已有研究表明，突触后膜AMPA受体内吞其介导的长时程抑制（LTD）与恐惧记忆消退密切相关，而自噬参与了LTD过程中突触后膜AMPA受体的内吞降解。我们前期研究证实自噬在条件恐惧记忆的巩固过程中发挥重要作用。进一步预实验发现，恐惧消退训练后杏仁核区自噬水平增加，采用药理学方法阻断自噬可抑制杏仁核突触的LTD，损伤恐惧记忆的消退。我们据此推测，恐惧消退训练可诱导自噬增加，自噬激活后通过选择性增加突触后膜AMPA受体的内吞，增强LTD，进而促进恐惧消退。本研究拟采用分子生物学、遗传学与行为学实验等相结合的方法，阐明恐惧消退模型中自噬的变化及作用，并结合电生理技术研究自噬对AMPA受体及突触可塑性的调控作用，探讨外源性诱导自噬易化恐惧消退的可能性，以期为焦虑类精神疾病的药物治疗提供新思路和新策略。

条件性恐惧记忆模型近年来多用于探索恐惧记忆相关精神疾病发病机制和治疗手段，恐惧记忆巩固是创伤后应激障碍（PTSD）症状不易消退的重要原因，近年有研究表明m6A甲基化酶METTL3及识别蛋白YTHDF1敲除后可抑制恐惧记忆，因此本项目通过行为学、脑片膜片钳、免疫组化及多组学研究，探讨了METTL3新型抑制剂STM2457及识别蛋白YTHDF2对恐惧记忆的调控作用及机制，本研究发现STM2457腹腔给药可通过抑制海马及前额皮层m6A修饰水平，降低突触组装及突触可塑性关键分子如BNDF、CAMK2a的RNA水平，损伤长期线索型恐惧记忆；而通过cre-loxp系统条件敲除海马及皮层的YTHDF2，会导致YTHDF2的靶基因mRNA稳定性增强，使海马区兴奋性突触传递增强，进而引起情景型恐惧记忆增强，过表达YTHDF2可逆转恐惧记忆水平。本研究结果揭示了m6A的甲基化酶METTL3及识别蛋白YTHDF2对恐惧记忆的双向调节机制，为研究恐惧记忆的形成及调控机制提供了新的思路，METTL3抑制剂STM2457也可也有望成为PTSD的潜在治疗药物，为后续的药物筛选提供新的方向。