Abstract: Objective Junctophilin-2 (JPH2) is an essential structural protein that maintains junctional membrane complexes (JMCs) in cardiomyocytes by tethering the plasma membrane to the sarcoplasmic reticulum, thereby facilitating excitation-contraction (E-C) coupling. Mutations in JPH2 have been associated with hypertrophic cardiomyopathy (HCM), but the molecular mechanisms governing its membrane-binding properties and the functional relevance of its membrane occupation and recognition nexus (MORN) repeat motifs remain incompletely understood. This study aimed to elucidate the structural basis of JPH2 membrane association and its implications for HCM pathogenesis.Methods A recombinant N-terminal fragment of mouse JPH2 (residues 1-440), encompassing the MORN repeats and an adjacent helical region, was purified under near-physiological buffer conditions. X-ray crystallography was employed to determine the structure of the JPH2 MORN-Helix domain. Sequence conservation analysis across species and junctophilin isoforms was performed to assess the evolutionary conservation of key structural features. Functional membrane-binding assays were conducted using liposome co-sedimentation and cell-based localization studies in COS7 and HeLa cells. In addition, site-directed mutagenesis targeting positively charged residues and known HCM-associated mutations, including R347C, was used to evaluate their effects on membrane interaction and subcellular localization.Results The crystal structure of the mouse JPH2 MORN-Helix domain was resolved at 2.6 ?, revealing a compact, elongated architecture consisting of multiple tandem MORN motifs arranged in a curved configuration, forming a continuous hydrophobic core stabilized by alternating aromatic residues. A C-terminal α-helix further reinforced structural integrity. Conservation analysis identified the inner groove of the MORN array as a highly conserved surface, suggesting its role as a protein-binding interface. A flexible linker segment enriched in positively charged residues, located adjacent to the MORN motifs, was found to mediate direct electrostatic interactions with negatively charged phospholipid membranes. Functional assays demonstrated that mutation of these basic residues impaired membrane association, while the HCM-linked R347C mutation completely abolished membrane localization in cellular assays, despite preserving the overall MORN-Helix fold in structural modeling.Conclusion This study provides structural insight into the membrane-binding mechanism of the cardiomyocyte-specific protein JPH2, highlighting the dual roles of its MORN-Helix domain in membrane anchoring and protein interactions. The findings clarify the structural basis for membrane targeting via a positively charged linker and demonstrate that disruption of this interaction—such as that caused by the R347C mutation—likely contributes to HCM pathogenesis. These results not only enhance current understanding of JPH2 function in cardiac E-C coupling but also offer a structural framework for future investigations into the assembly and regulation of JMCs in both physiological and disease contexts.
Abstract: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline, functional impairment, and neuropsychiatric symptoms. It represents the most prevalent form of dementia among the elderly population. Accumulating evidence indicates that oxidative stress plays a pivotal role in the pathogenesis of AD. Notably, elevated levels of oxidative stress have been observed in the brains of AD patients, where excessive reactive oxygen species (ROS) can cause extensive damage to lipids, proteins, and DNA, ultimately compromising neuronal structure and function. β-amyloid (Aβ) has been shown to induce mitochondrial dysfunction and calcium overload, thereby promoting the generation of reactive oxygen species (ROS). This, in turn, exacerbates Aβ aggregation and enhances tau phosphorylation, leading to the formation of two pathological features of AD: extracellular Aβ plaque deposition and intracellular neurofibrillary tangles (NFTs). These events ultimately culminate in neuronal death, forming a vicious cycle. The interplay between oxidative stress and these pathological processes constitutes a core link in the pathogenesis of AD. The signaling pathways mediating oxidative stress in AD include Nrf2, RCAN1, PP2A, CREB, Notch1, NF-κB, ApoE, and ferroptosis. The Nrf2 signaling pathway serves as a key regulator of cellular redox homeostasis, exerts important antioxidant capacity and protective effects in AD. The RCAN1 signaling pathway, as a calcineurin inhibitor, and modulates AD progression through multiple mechanisms. The PP2A signaling pathway is involved in regulating tau phosphorylation and neuroinflammation processes. The CREB signaling pathway contributes to neuroplasticity and memory formation; activation of CREB improves cognitive function and reduce oxidative stress. The Notch1 signaling pathway regulates neuronal development and memory, participates in modulation of Aβ production, and interacts with Nrf2 to co-regulate antioxidant activity. The NF-κB signaling pathway governs immune and inflammatory responses; sustained activation of this pathway forms "inflammatory memory," thereby exacerbating AD pathology. The ApoE signaling pathway is associated with lipid metabolism; among its isoforms, ApoE-ε4 significantly increases the risk of AD, leading to elevated oxidative stress, abnormal lipid metabolism, and neuroinflammation. The ferroptosis signaling pathway is driven by iron-dependent lipid peroxidation, and the subsequent release of lipid peroxidation products and ROS exacerbate oxidative stress and neuronal damage. These interconnected pathways form a complex regulatory network that regulates the progression of AD through oxidative stress and related pathological cascades. In terms of therapeutic strategies targeting oxidative stress, among the drugs currently used in clinical practice for AD treatment, memantine and donepezil demonstrate significant therapeutic efficacy and can improve the level of oxidative stress in AD patients. Some compounds with antioxidant effects (such as α-lipoic acid and melatonin) have shown certain potential in AD treatment research and can be used as dietary supplements to ameliorate AD symptoms. In addition, non-drug interventions such as calorie restriction and exercise have been proven to exerted neuroprotective effects and have a positive effect on the treatment of AD. By comprehensively utilizing the therapeutic characteristics of different signaling pathways, it is expected that more comprehensive multi-target combination therapy regimens and combined nanomolecular delivery systems will be developed in the future to bypass the blood-brain barrier, providing more effective therapeutic strategies for AD.
Abstract: Schizophrenia is a severe psychiatric disorder characterized by positive symptoms (e.g., hallucinations), negative symptoms (e.g., social withdrawal), and cognitive impairments. Cognitive impairment is a core symptom of patients with schizophrenia, severely impairing their social function and long-term prognosis. Antipsychotics, the first-line treatment for schizophrenia, effectively manage positive symptoms in most patients. However, their efficacy in alleviating negative and cognitive deficits is limited. Moreover, long-term use may lead to syndrome and extrapyramidal side effects. Consequently, non-pharmacological interventions have gained significant attention as alternative or adjunctive strategies for cognitive remediation in schizophrenia. In recent years, non-pharmacological intervention techniques grounded in neuroplasticity theory have developed rapidly. These techniques provide new perspectives for alleviating cognitive impairment in schizophrenia by regulating neural circuits (e.g., enhancing prefrontal-hippocampal connection function) and synaptic plasticity (e.g., modulating the BDNF/TrkB pathway) from multiple dimensions. These novel interventions not only enhance cognitive function but also mitigate medication-related adverse effects and improve patient treatment compliance. This article comprehensively reviews the clinical evidence and technical advancements of non-pharmacological interventions for treating cognitive impairments in schizophrenia, the interventions covered include cognitive remediation therapy (CRT), repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), electro-acupuncture (EA), aerobic exercise (AE), and light therapy (LT). CRT, the most extensively studied and evidence-based intervention, employs structured cognitive training tasks to enhance neuroplasticity and has consistently demonstrated efficacy in improving executive function and social cognition. Both rTMS and tDCS are non-invasive brain stimulation techniques that modulate cortical excitability and neural network connectivity. While rTMS has shown potential in enhancing working memory and attention, especially in patients with prominent negative symptoms, its clinical efficacy remains inconsistent across studies, possibly due to variability in stimulation parameters and patient heterogeneity. tDCS, on the other hand, has demonstrated promising effects on working memory and attention, with a relatively rapid onset of action, though optimal protocols are yet to be standardized. EA integrates traditional acupuncture with electrical stimulation and has been shown to improve memory function, likely through upregulation of brain-derived neurotrophic factor (BDNF) and enhancement of cerebral blood flow. It may be particularly beneficial in treatment-resistant cases. AE, a low-cost and accessible intervention, promotes hippocampal neuroplasticity and BDNF expression, leading to improvements in memory and attention. It is recommended as a foundational adjunctive therapy, especially in chronic patients. LT, though still in the experimental stage, has shown promising results in animal models by modulating neuroinflammation and enhancing neurogenesis via the BDNF/CREB signaling pathway. However, clinical evidence remains limited, and further large-scale trials are needed to validate its efficacy and safety. In addition to reviewing individual interventions, the review highlights the potential of combination strategies, such as CRT paired with AE or rTMS, to produce synergistic cognitive benefits. Future directions include personalized treatment protocols, early intervention during neurodevelopmental windows (e.g., adolescence), and the integration of biomarkers and neuroimaging to guide therapy. This synthesis aims to provide clinicians and researchers with a comprehensive framework for advancing non-pharmacological cognitive rehabilitation in schizophrenia.
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