Synaptic protein S-palmitoylation as a novel mechanism underlying sex-dependent differences in neuronal plasticity

Although sex differences in the brain are prevalent, the knowledge about mechanisms underlying sex-related effects on normal and pathological brain functioning is rather poor. It is known that female and male brains differ in size and connectivity. Moreover, those differences are related to neuronal morphology and activity, synapse molecular organization, synaptic plasticity, and molecular signalling pathways. Among different processes assuring proper synapse function are posttranslational modifications, and among them, S-palmitoylation emerges as a crucial mechanism underlying synaptic integrity. Protein S-palmitoylation (S-PALM) refers to the covalent attachment of palmitic acid (C16:0) to cysteine residue(s) via the formation of a thioester bond. Protein S-PALM is governed by a family of PATs, also known as DHHC proteins. Here we focused on the sex-related functional importance of DHHC7 acyltransferase. Under physiological conditions, DHHC7 emerges of particular interest because it palmitoylates various synaptic proteins involved in the regulation of cellular polarity and proliferation as well as in stress and anxiety-related pathology. Moreover, DHHC7 is responsible for S-PALM of sex steroid receptors. Functionally, S-PALM of these receptors regulates their trafficking to the plasma membrane as well as their rapid responses to sex steroid hormones. Using mass spectrometry-based method PANIMoni we identified sex-dependent differences in the S-palmitoylation of synaptic proteins, potentially involved in the regulation of passive membrane properties and excitability (e.g. potassium voltage-gated channels), synaptic transmission (e.g. subunits of glutamate or kainate receptors, voltage-dependent calcium channels) as well as signalling proteins involved in structural plasticity of dendritic spines (e.g. G-proteins and Rab GTPase). Furthermore, to determine a mechanistic source for sex-dependent changes in protein S-palmitoylation we used synaptoneurosomes from DHHC-7 knock-out -/- (DHHC7 KO) female and male mice. Our data showed sex-dependent action of DHHC-7 acyltransferase. Such discovery will facilitate the development of novel and targeted treatments congruous with biological sex.

尽管大脑中的性别差异普遍存在，但目前学界对性别因素影响正常与病理性大脑功能的潜在机制仍知之甚少。已知雌性与雄性大脑在体积及连接模式上存在差异，且这些差异与神经元形态、活性、突触分子组织、突触可塑性及分子信号通路密切相关。保障突触正常功能的诸多过程中，翻译后修饰发挥着关键作用，其中S-棕榈酰化（S-palmitoylation）已被证实是维持突触完整性的核心机制之一。蛋白质S-棕榈酰化（S-PALM）指通过形成硫酯键，将棕榈酸（C16:0）共价结合至半胱氨酸残基的修饰过程，该修饰由PAT家族酶调控，这类酶又被称为DHHC蛋白。本研究聚焦于DHHC7酰基转移酶的性别相关功能重要性。在生理条件下，DHHC7备受关注，因其可对多种参与细胞极性、增殖调控以及应激与焦虑相关病理过程的突触蛋白进行棕榈酰化修饰。此外，DHHC7还负责性别类固醇受体的S-棕榈酰化修饰。功能层面上，这类受体的S-棕榈酰化修饰可调控其向质膜的转运，以及对性别类固醇激素的快速应答反应。我们借助基于质谱技术的PANIMoni方法，鉴定出突触蛋白的S-棕榈酰化存在性别依赖性差异，这些蛋白可能参与静息膜特性与兴奋性的调控（如电压门控钾通道）、突触传递（如谷氨酸或红藻氨酸受体亚基、电压依赖性钙通道），以及树突棘结构可塑性相关的信号蛋白（如G蛋白与Rab GTP酶）。为明确蛋白质S-棕榈酰化的性别依赖性变化的机制根源，我们使用了DHHC7敲除纯合子（DHHC7 KO）雌性与雄性小鼠的突触神经小体。研究数据表明，DHHC7酰基转移酶的作用存在性别依赖性。这一发现将有助于开发与生物学性别相适配的新型靶向治疗方案。