Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Department of Pain Clinic, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China.
J Physiol. 2018 Apr 1;596(7):1259-1276. doi: 10.1113/JP275147. Epub 2018 Feb 21.
Shank3 increases the HCN channel surface expression in heterologous expression systems. Shank3 deficiency causes significant reduction in HCN2 expression and I current amplitude in thalamocortical (TC) neurons. Shank3 - but not Shank3 -deficient TC neurons share changes in basic electrical properties which are comparable to those of HCN2-/- TC neurons. HCN channelopathy may critically mediate events downstream from Shank3 deficiency.
SHANK3 is a scaffolding protein that is highly enriched in excitatory synapses. Mutations in the SHANK3 gene have been linked to neuropsychiatric disorders especially the autism spectrum disorders. SHANK3 deficiency is known to cause impairments in synaptic transmission, but its effects on basic neuronal electrical properties that are more localized to the soma and proximal dendrites remain unclear. Here we confirmed that in heterologous expression systems two different mouse Shank3 isoforms, Shank3A and Shank3C, significantly increase the surface expression of the mouse hyperpolarization-activated, cyclic-nucleotide-gated (HCN) channel. In Shank3 knockout mice, which lack exons 13-16 in the Shank3 gene (both Shank3A and Shank3C are removed) and display a severe behavioural phenotype, the expression of HCN2 is reduced to an undetectable level. The thalamocortical (TC) neurons from the ventrobasal (VB) complex of Shank3 mice demonstrate reduced I current amplitude and correspondingly increased input resistance, negatively shifted resting membrane potential, and abnormal spike firing in both tonic and burst modes. Impressively, these changes closely resemble those of HCN2-/- TC neurons but not of the TC neurons from Shank3 mice, which lack exons 4-9 in the Shank3 gene (Shank3C still exists) and demonstrate moderate behavioural phenotypes. Additionally, Shank3 deficiency increases the ratio of excitatory/inhibitory balance in VB neurons but has a limited impact on the electrical properties of connected thalamic reticular (RTN) neurons. These results provide new understanding about the role of HCN channelopathy in mediating detrimental effects downstream from Shank3 deficiency.
Shank3 可增加异源表达系统中 HCN 通道的表面表达。Shank3 缺失导致丘脑皮质（TC）神经元中 HCN2 表达和 I 电流幅度显著减少。Shank3-/-TC 神经元具有相似的基本电生理特性改变，而 Shank3 缺失的 TC 神经元则具有这些改变。HCN 通道病可能在 Shank3 缺失的下游事件中起关键作用。
SHANK3 是一种富含兴奋性突触的支架蛋白。SHANK3 基因的突变与神经精神疾病有关，特别是自闭症谱系障碍。已知 Shank3 缺失会导致突触传递受损，但它对更局限于胞体和近端树突的基本神经元电生理特性的影响尚不清楚。在这里，我们证实两种不同的小鼠 Shank3 异构体 Shank3A 和 Shank3C 在异源表达系统中显著增加了小鼠超极化激活、环核苷酸门控（HCN）通道的表面表达。在 Shank3 基因缺失外显子 13-16（Shank3A 和 Shank3C 均被删除）且表现出严重行为表型的 Shank3 敲除小鼠中，HCN2 的表达减少到无法检测的水平。Shank3 敲除小鼠腹侧基底复合体（VB）的 TC 神经元的 I 电流幅度减小，相应的输入电阻增加，静息膜电位负移，在紧张和爆发模式下的尖峰放电异常。令人印象深刻的是，这些变化与 HCN2-/-TC 神经元非常相似，但与 Shank3 基因缺失外显子 4-9（Shank3C 仍然存在）且表现出中度行为表型的 TC 神经元不同。此外，Shank3 缺失增加了 VB 神经元中兴奋性/抑制性平衡的比值，但对连接的丘脑网状（RTN）神经元的电生理特性影响有限。这些结果为了解 Shank3 缺失下游的 HCN 通道病在介导有害影响中的作用提供了新的认识。
