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S-Palmitoylation of Synaptic Proteins as a Novel Mechanism Underlying Sex-Dependent Differences in Neuronal Plasticity.

ABSTRACT: 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, synaptic plasticity, and molecular signaling pathways. Among different processes assuring proper synapse functions are posttranslational modifications, and among them, S-palmitoylation (S-PALM) emerges as a crucial mechanism regulating synaptic integrity. Protein S-PALM is governed by a family of palmitoyl acyltransferases, also known as DHHC proteins. Here we focused on the sex-related functional importance of DHHC7 acyltransferase because of its S-PALM action over different synaptic proteins as well as sex steroid receptors. Using the mass spectrometry-based PANIMoni method, we identified sex-dependent differences in the S-PALM of synaptic proteins potentially involved in the regulation of membrane excitability and synaptic transmission as well as in the signaling of proteins involved in the structural plasticity of dendritic spines. To determine a mechanistic source for obtained sex-dependent changes in protein S-PALM, we analyzed synaptoneurosomes isolated from DHHC7-/- (DHHC7KO) female and male mice. Our data showed sex-dependent action of DHHC7 acyltransferase. Furthermore, we revealed that different S-PALM proteins control the same biological processes in male and female synapses.

SUBMITTER: Zareba-Koziol M

PROVIDER: S-EPMC8230572 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description: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.

Project description:Donnai-Barrow syndrome, a genetic disorder associated to LRP2 (low-density lipoprotein receptor 2/megalin) mutations, is characterized by unexplained neurological symptoms and intellectual deficits. Megalin is a multifunctional endocytic clearance cell-surface receptor, mostly described in epithelial cells. This receptor is also expressed in the CNS, mainly in neurons, being involved in neurite outgrowth and neuroprotective mechanisms. Yet, the mechanisms involved in the regulation of megalin in the CNS are poorly understood. Using transthyretin knockout mice, a megalin ligand, we found that transthyretin positively regulates neuronal megalin levels in different CNS areas, particularly in the hippocampus. Transthyretin is even able to rescue megalin downregulation in transthyretin knockout hippocampal neuronal cultures, in a positive feedback mechanism via megalin. Importantly, transthyretin activates a regulated intracellular proteolysis mechanism of neuronal megalin, producing an intracellular domain, which is translocated to the nucleus, unveiling megalin C-terminal as a potential transcription factor, able to regulate gene expression. We unveil that neuronal megalin reduction affects physiological neuronal activity, leading to decreased neurite number, length and branching, and increasing neuronal susceptibility to a toxic insult. Finally, we unravel a new unexpected role of megalin in synaptic plasticity, by promoting the formation and maturation of dendritic spines, and contributing for the establishment of active synapses, both in in vitro and in vivo hippocampal neurons. Moreover, these structural and synaptic roles of megalin impact on learning and memory mechanisms, since megalin heterozygous mice show hippocampal-related memory and learning deficits in several behaviour tests. Altogether, we unveil a complete novel role of megalin in the physiological neuronal activity, mainly in synaptic plasticity with impact in learning and memory. Importantly, we contribute to disclose the molecular mechanisms underlying the cognitive and intellectual disabilities related to megalin gene pathologies.

Project description:The basolateral amygdala (BLA) integrates sensory input from cortical and subcortical regions, a function that requires marked synaptic plasticity. Here we provide evidence that cytochrome P450 aromatase (AROM), the enzyme converting testosterone to 17?-estradiol (E2), contributes to the regulation of this plasticity in a sex-specific manner. We show that AROM is expressed in the BLA, particularly in the basolateral nucleus (BL), in male and female rodents. Systemic administration of the AROM inhibitor letrozole reduced spine synapse density in the BL of adult female mice but not in the BL of male mice. Similarly, in organotypic corticoamygdalar slice cultures from immature rats, treatment with letrozole significantly reduced spine synapses in the BL only in cultures derived from females. In addition, letrozole sex-specifically altered synaptic properties in the BL: in acute slices from juvenile (prepubertal) female rats, wash-in of letrozole virtually abolished long-term potentiation (LTP), whereas it did not prevent the generation of LTP in the slices from males. Together, these data indicate that neuron-derived E2 modulates synaptic plasticity in rodent BLA sex-dependently. As protein expression levels of AROM, estrogen and androgen receptors did not differ between males and females and were not sex-specifically altered by letrozole, the findings suggest sex-specific mechanisms of E2 signaling.SIGNIFICANCE STATEMENT The basolateral amygdala (BLA) is a key structure of the fear circuit. This research reveals a sexually dimorphic regulation of synaptic plasticity in the BLA involving neuronal aromatase, which produces the neurosteroid 17?-estradiol (E2). As male and female neurons in rodent BLA responded differently to aromatase inhibition both in vivo and in vitro, our findings suggest that E2 signaling in BLA neurons is regulated sex-dependently, presumably via mechanisms that have been established during sexual determination. These findings could be relevant for the understanding of sex differences in mood disorders and of the side effects of cytochrome P450 aromatase inhibitors, which are frequently used for breast cancer therapy.

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S-Palmitoylation of Synaptic Proteins as a Novel Mechanism Underlying Sex-Dependent Differences in Neuronal Plasticity.

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