The role of serine proteases in synaptic plasticity of mouse visual cortex

感觉体验通过未知的过程在出生后早期重新连接大脑1)我们在视觉皮质的第2/3层发现了单眼剥夺(MD)的强大解剖后果，对应于在轴突输入发生任何变化之前迅速的、功能性的反应丧失。锥体细胞顶端树突上的突起在睁开眼睛后稳步增加，但在生理关键期经过短暂的MD后，通过竞争机制暂时消失。相反，组织型纤溶酶原激活剂(TPA)对蛋白质的分解作用随着年龄的增长而下降，只有在幼龄小鼠中，MD才会增加。靶向阻断tPA释放或谷氨酸脱羧酶(GAD65)对tPA上游调节的作用可防止伴有关键期可塑性的药物抢救的MD所致的脊柱丢失。2)通过感觉剥夺、兴奋性皮质内或丘脑皮质轴突终末和…来探索相应的快速和局部突触前细化囊泡型谷氨酸转运体(VGlut)1和vGlut2分别在BZ区有更多的表达。在CP期间，短暂单眼剥夺(4dMD)后，vGlut2在第IV层附近的免疫反应减弱。有趣的是，与4dMD相比，TTX注射的对侧BZ对闭眼的所有层的这两个信号都低于同侧BZ，这导致了更强的功能漂移和树突的快速细化。这些结果表明，兴奋性输入的快速和局部功能丧失可能与经验依赖的竞争修剪树突棘有关。3)我们研究了tPA对细胞外基质(ECM)的特定作用。在成年野生型(WT)和tPA KO小鼠中，与紫藤凝集素(WFA)结合的神经周围神经网络正常出现，主要位于双眼区(BZ)的IVN层。4)我们探索了tPA介导的小鼠视皮层蛋白分解的潜在底物。活性酶纤溶酶以剂量和时间依赖的方式观察到胞外蛋白的有限降解。较少

Sensory experience physically rewires the brain in early postnatal life through unknown processes.1) We identified a robust anatomical consequence of monocular deprivation (MD) in layer 2/3 of visual cortex that corresponds to the rapid, functional loss of responsiveness preceding any changes in axonal input. Protrusions on pyramidal cell apical dendrites increased steadily after eye-opening, but were transiently lost through competitive mechanisms after brief MD during the physiological critical period. Proteolysis by tissue-type plasminogen activator (tPA) conversely declined with age and increased upon MD only in young mice. Targeted disruption of tPA release or its upstream regulation by glutamic acid decarboxylase (GAD65) prevented spine loss by MD that was pharmacologically rescued concomitant with critical period plasticity.2) To explore correspondingly rapid and local pre-synaptic refinements by sensory deprivation, excitatory intracortical or thalamocortical axon terminals wer … More e visualized in the BZ by vesicular glutamate transporters (vGlut)1 and vGlut2, respectively. The immunoreactivity of vGlut2 decreased around layer IV by brief monocular deprivation (4dMD) during the CP. Interestingly, both signals in all layers were lower in the contralateral BZ to the closed eye than that in the ipsilateral BZ by TTX injections, that induces stronger effect in functional shifts and rapid dendritic refinement compared to 4dMD. These results suggest that rapid and local functional loss of excitatory inputs may correlate with dendritic spine pruning by experience-dependent competition.3) We examined a specific role for tPA upon the extracellular matrix (ECM). Perineuronal nets bound to wisteria floribunda agglutinin (WFA) appeared normally in adult wild-type (WT) and tPA KO mice, primarily in layer IVN of the binocular zone (BZ).4) We explored potential substrates for tPA-mediated proteolysis in mouse visual cortex. Limited proteolysis of extracellular proteins was observed in a dose-and time-dependent manner by active enzyme plasmin. Less