Title: beta Hydroxybutyrate Targets C99 Driven Organelle Disruption in a Drosophila Model of Alzheimers Disease Show Chinese title

Title: β-羟基丁酸靶向果蝇阿尔茨海默病模型中由C99驱动的细胞器破坏

Abstract: The amyloid precursor protein (APP)-derived fragment C99 has emerged as a central driver of subcellular dysfunction in Alzheimers disease (AD), yet its precise interactome and contribution to mitochondrial and autophagy-lysosomal disruption remain incompletely defined. Here, we performed quantitative proteomic mapping of C99 associated proteins in a Drosophila AD model and identified three major functional modules nuclear gene expression, mitochondrial metabolism, and autophagy regulation frequently disrupted in AD. Among these, several C99 interactors showed altered association upon treatment with beta-hydroxybutyrate (BHB), a metabolic ketone body with emerging neuroprotective properties. Ultrastructural analysis revealed that C99 expression induced severe mitochondrial fragmentation, cristae loss, and the accumulation of dense vesicles with fibrillar contents, indicative of impaired organelle integrity and degradative failure. These abnormalities were substantially reversed by BHB treatment, which restored mitochondrial architecture, improved lysosomal acidification, and reduced the burden of aberrant vesicles. Functional assays confirmed that BHB also rescued lifespan and memory deficits in C99-expressing flies. Further, expression of selected C99 interactors such as PPME1 and VPS35 was sufficient to ameliorate neurodegenerative phenotypes in vivo, underscoring their functional relevance. Together, our findings define a multi-axis cellular pathology driven by C99 accumulation and demonstrate that metabolic intervention via BHB can reprogram disrupted proteomic networks and organelle homeostasis. These results establish a mechanistic link between ketone signaling and early subcellular dysfunction in AD, offering potential new targets for therapeutic intervention. Show Chinese abstract

Abstract: 淀粉样前体蛋白（APP）衍生片段C99已成为阿尔茨海默病（AD）中亚细胞功能障碍的核心驱动因素，但其精确的相互作用组及其对线粒体和自噬-溶酶体破坏的贡献仍不完全明确。 在此，我们对果蝇AD模型中与C99相关的蛋白质进行了定量蛋白质组学映射，并鉴定了三个主要功能模块：核基因表达、线粒体代谢和自噬调节，在AD中经常受到破坏。 其中，一些C99相互作用蛋白在使用β-羟基丁酸（BHB）处理后表现出改变的关联性，BHB是一种具有新兴神经保护特性的代谢酮体。 超结构分析显示，C99的表达引发了严重的线粒体碎片化、嵴丢失以及富含纤维内容物的致密囊泡积累，表明细胞器完整性受损和降解失败。 这些异常被BHB治疗显著逆转，BHB恢复了线粒体结构，改善了溶酶体酸化，并减少了异常囊泡的负担。 功能实验证实，BHB还能挽救表达C99的果蝇的寿命和记忆缺陷。 此外，表达选定的C99相互作用蛋白如PPME1和VPS35足以在体内缓解神经退行性表型，强调了它们的功能相关性。 总之，我们的研究定义了一种由C99积累驱动的多轴细胞病理，并证明通过BHB的代谢干预可以重新编程受干扰的蛋白质组网络和细胞器稳态。 这些结果建立了一种酮体信号传导与AD早期亚细胞功能障碍之间的机制联系，为治疗干预提供了潜在的新靶点。