Shank3 is a synaptic scaffolding protein that assists in tethering and organizing structural proteins and glutamatergic receptors in the postsynaptic density of excitatory synapses. The localization of Shank3 at excitatory synapses and the formation of stable Shank3 complexes is regulated by the binding of zinc to the C-terminal sterile-alpha-motif (SAM) domain of Shank3. Mutations in the SAM domain of Shank3 result in altered synaptic function and morphology, and disruption of zinc in synapses that express Shank3 leads to a reduction of postsynaptic proteins important for synaptic structure and function. This suggests that zinc supports the localization of postsynaptic proteins via Shank3. Many regions of the brain are highly enriched with free zinc inside glutamatergic vesicles at presynaptic terminals. At these synapses, zinc transporter 3 (ZnT3) moves zinc into vesicles where it is co-released with glutamate. Alterations in ZnT3 are implicated in multiple neurodevelopmental disorders, and ZnT3 knock-out (KO) mice—which lack synaptic zinc—show behavioral deficits associated with autism spectrum disorder and schizophrenia. Here we show that male and female ZnT3 KO mice have smaller dendritic spines and miniature excitatory postsynaptic current amplitudes than wildtype (WT) mice in the auditory cortex. Additionally, spine size deficits in ZnT3 KO mice are restricted to synapses that express Shank3. In WT mice, synapses that express both Shank3 and ZnT3 have larger spines compared to synapses that express Shank3 but not ZnT3. Together these findings suggest a mechanism whereby presynaptic ZnT3-dependent zinc supports postsynaptic structure and function via Shank3 in a synapse-specific manner.

Shank3 是一种突触支架蛋白，有助于在兴奋性突触的突触后密度中束缚和组织结构蛋白和谷氨酸受体。 Shank3 在兴奋性突触的定位和稳定 Shank3 复合物的形成是通过锌与 Shank3 的 C 端不育 α 基序 (SAM) 结构域的结合来调节的。 Shank3 的 SAM 结构域突变会导致突触功能和形态发生改变，表达 Shank3 的突触中锌的破坏会导致对突触结构和功能很重要的突触后蛋白减少。这表明锌通过 Shank3 支持突触后蛋白的定位。大脑的许多区域在突触前末端的谷氨酸能小泡内富含游离锌。在这些突触处，锌转运蛋白 3 (ZnT3) 将锌转移到囊泡中，并与谷氨酸共同释放。 ZnT3 的改变与多种神经发育障碍有关，而缺乏突触锌的 ZnT3 敲除 (KO) 小鼠表现出与自闭症谱系障碍和精神分裂症相关的行为缺陷。在这里，我们发现雄性和雌性 ZnT3 KO 小鼠在听觉皮层中比野生型 (WT) 小鼠具有更小的树突棘和微型兴奋性突触后电流振幅。此外，ZnT3 KO 小鼠的脊柱大小缺陷仅限于表达 Shank3 的突触。在 WT 小鼠中，与表达 Shank3 但不表达 ZnT3 的突触相比，表达 Shank3 和 ZnT3 的突触具有更大的刺。这些发现共同表明了一种机制，即突触前 ZnT3 依赖性锌通过 Shank3 以突触特异性方式支持突触后结构和功能。