The interaction of Synapsin 2a and Synaptogyrin-3 regulates fear extinction in mice
Xi-Ya Shen, … , Ling-Qiang Zhu, Dan Liu
Xi-Ya Shen, … , Ling-Qiang Zhu, Dan Liu
Published January 4, 2024
Citation Information: J Clin Invest. 2024;134(4):e172802. https://doi.org/10.1172/JCI172802.
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Research Article Neuroscience

The interaction of Synapsin 2a and Synaptogyrin-3 regulates fear extinction in mice

Abstract

The mechanisms behind a lack of efficient fear extinction in some individuals are unclear. Here, by employing a principal components analysis–based approach, we differentiated the mice into extinction-resistant and susceptible groups. We determined that elevated synapsin 2a (Syn2a) in the infralimbic cortex (IL) to basolateral amygdala (BLA) circuit disrupted presynaptic orchestration, leading to an excitatory/inhibitory imbalance in the BLA region and causing extinction resistance. Overexpression or silencing of Syn2a levels in IL neurons replicated or alleviated behavioral, electrophysiological, and biochemical phenotypes in resistant mice. We further identified that the proline-rich domain H in the C-terminus of Syn2a was indispensable for the interaction with synaptogyrin-3 (Syngr3) and demonstrated that disrupting this interaction restored extinction impairments. Molecular docking revealed that ritonavir, an FDA-approved HIV drug, could disrupt Syn2a-Syngr3 binding and rescue fear extinction behavior in Syn2a-elevated mice. In summary, the aberrant elevation of Syn2a expression and its interaction with Syngr3 at the presynaptic site were crucial in fear extinction resistance, suggesting a potential therapeutic avenue for related disorders.

Authors

Xi-Ya Shen, Juan Zhang, He-Zhou Huang, Shao-Dan Li, Ling Zhou, Shi-Ping Wu, Cheng Tang, Xian Huang, Zhi-Qiang Liu, Zi-Yuan Guo, Xiang Li, Heng-Ye Man, You-Ming Lu, Ling-Qiang Zhu, Dan Liu

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Figure 5

Syn2a blocked the presynaptic vesicle releasing via its H domain.

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Syn2a blocked the presynaptic vesicle releasing via its H domain. (A) Th...
(A) The presynaptic fraction of mPFC homogenates was prepared and then immunoprecipitated by using anti-VAMP2. The pellets were then subjected for immunoblot with the antibodies of anti-Syntaxin, anti-SNAP25 and anti-Syn2a. The representative blots (left) and the quantitative analysis (right) were shown (n = 3 per group). (B) Graphic diagram illustrating the differences in protein domains among WT Syn2b, Syn2a, and 2 Syn2a mutants. (C) Average freezing response for all trials during fear acquisition, extinction retrieval, and extinction of control, AAV-Syn2a, AAV-Syn2a-ΔH, and AAV-Syn2a-ΔE groups in mice. (D and E) Freezing response during the extinction training (D) and testing sessions (E) of control, AAV-Syn2a, AAV-Syn2a-ΔH, and AAV-Syn2a-ΔE groups in mice (n = 6–7 per group). (F) Paired-pulse ratios recorded from sEPSC amplitudes. (G–I) The primary cortical neurons were transfected with EGFP-C1, EGFP-Syn2a, EGFP-Syn2a-ΔH, or EGFP-Syn2a-ΔE plasmid at DIV 7. Then the FM4-64 releasing experiment was performed with a time-series based procedure at DIV 14. The representative confocal images (G) were shown. Pre: before the 90 mM KCl stimulation; Post: after the 90 mM KCl stimulation; pseudo color images indicate the change in FM4-64 fluorescent values (post–pre). Scale bar: 100 μm. The kinetics of FM4-64 fluorescence recorded from approximately 20 seconds before to approximately100 seconds after K+ stimulation are shown in H. The single-exponential decay functions were fitted to the diagrams with fluorescence intensity changes of FM4-64 analyzed by Image J software (left) and the time constant τ (right) were analyzed (I) (n = 3 independent experiments). Statistical analyses among multiple groups were conducted using 1-way (D, E, F, and I) or 2-way (A and C) ANOVA followed by Bonferroni post hoc tests. *P < 0.05, **P < 0.01, and ***P < 0.001. Values are presented as mean ± SEM.