Mitochondrial dysfunction is a key feature of many neurodegenerative diseases, including Huntington’s disease (HD), yet the initiating cellular lesion that links the disease-causing protein, mutant huntingtin (mtHtt), to organelle failure and neuronal degeneration remains unclear. Using complementary in vitro and in vivo models of HD, we investigated the molecular mechanisms by which mtHtt disrupts mitochondrial integrity and identified its mitochondrial target whose perturbation leads to cristae disorganization and subsequent neuronal degeneration. The pathogenic relevance of this pathway was further evaluated in HD patient iPSC-derived striatal neurons and HD knock-in mice through genetic manipulation, where behavioral assays, neuropathological analyses, and electron microscopy were employed to assess disease progression and mitochondrial ultrastructure. We show that mutant huntingtin (mtHtt) destabilizes mitochondrial membrane architecture through disruption of the mitochondrial contact site and cristae organizing system (MICOS). Across neuronal and mouse models HD, the MICOS complex is disassembled and its core scaffold protein mitofilin is depleted. Mechanistically, mtHtt accumulates at mitochondrial contact sites, associates with mitofilin, and recruits the AAA-ATPase VCP/p97, which drives ATPase-dependent extraction of mitofilin from MICOS, leading to cristae disorganization, respiratory impairment, and structural destabilization. Extracted mitofilin accumulates in insoluble assemblies with mtHtt and VCP, reducing the soluble pool required to maintain crista junctions. Blocking VCP mitochondrial recruitment or inhibiting its ATPase activity preserves MICOS integrity, while restoring mitofilin reconstitutes cristae architecture, improves mitochondrial and synaptic function in patient-derived neurons, and ameliorates neuropathology and motor deficits in HD mice. These findings identify mitochondrial cristae architecture as a point of vulnerability in neurodegeneration and establish architectural destabilization of organelles as an upstream pathogenic mechanism linking disease proteins to neuronal degeneration.
Abstract Distinguishing resident microglia from infiltrating myeloid cells in stroke scRNA-seq data remains challenging due to shared myeloid markers; SALL1 shows greater specificity for microglia compared with commonly used markers (e.g. TMEM119, CX3CR1, P2RY12), and combining SALL1 with these commonly used markers improves the ability to distinguish microglia from infiltrating myeloid populations in stroke‑associated scRNA‑seq datasets.
Genetic and proteomic studies have identified numerous candidate genes associated with Alzheimer’s disease (AD), yet the functional relevance of many remains unclear. Islet Cell Autoantigen 1 Like (ICA1L) has consistently emerged as a top-ranked locus in integrative genome-wide and proteome-wide association studies, but its mechanistic role in AD pathogenesis has not been defined. ICA1L expression was examined in postmortem human AD brains and 5xFAD transgenic mice. Cognitive function and amyloid pathology were assessed using three independent ICA1L-deficient mouse models, including germline knockout, central nervous system-specific and excitatory neuron–specific knockouts. Hippocampal ICA1L overexpression was employed to evaluate the effects of enhanced ICA1L expression in vivo. ICA1L-interacting proteins were identified by immunoprecipitation followed by liquid chromatography–tandem mass spectrometry (LC-MS). Protein stability and degradation pathways were assessed using cycloheximide chase assays together with ubiquitination and inhibitor-based analyses. A structure-guided 30–amino acid ICA1L-derived peptide was engineered and evaluated for blood–brain barrier penetration and therapeutic efficacy in 5xFAD mice. ICA1L expression was significantly upregulated in the brains of AD patients and 5xFAD mice. Genetic ablation of ICA1L markedly exacerbated cognitive deficits and amyloid-β (Aβ) pathology, whereas hippocampal overexpression of ICA1L attenuated amyloid deposition and improved cognitive function. Interactomics analyses revealed that ICA1L physically interacts with low-density lipoprotein receptor-related protein 1 (LRP1). Loss of ICA1L accelerated LRP1 degradation via ubiquitin–proteasome pathways, resulting in increased BACE1 expression and enhanced Aβ production. Notably, a 30–amino acid synthetic peptide derived from ICA1L stabilized LRP1, alleviated Aβ pathology, and improved cognitive performance in 5xFAD mice. These findings identify ICA1L as an endogenous neuroprotective regulator of AD pathology and uncover a previously unrecognized ICA1L–LRP1 axis that modulates Aβ homeostasis. Targeting ICA1L or its active peptide represents a promising therapeutic strategy for Alzheimer’s disease.
Defective mitophagy is a key pathological risk of Alzheimer’s disease (AD), yet available pharmacological agents capable of restoring mitophagy remain clinically limited, largely due to the lack of tools for drug screening and target identification. To address this, we introduce an integrated platform with three novel artificial intelligence (AI)-enabled approaches—the phenotype-based screening model ‘CellAutoFM’, the drug-likeness predictor ‘ADMET Ranker’, and the target deconvolution method ‘PROCAT’. Using this platform together with wet lab validation, Crassifolin A (JGX-1) is identified as a potent natural product-derived mitophagy inducer; structurally, JGX-1 directly binds to ATP-binding cassette sub-family A member 1 (ABCA1) and sub-family G member 1 (ABCG1), triggering enhanced cholesterol efflux which activates PINK1/Parkin-dependent mitophagy. In both in vitro and in vivo AD laboratory models, JGX-1 reduces amyloid-β and Tau pathologies in an autophagy/mitophagy-dependent manner as these benefits are dramatically blunted with key mitophagy genes knocked down. Collectively, we provide an open-access, reproducible AI-assisted platform for rapid compound screening, drug-likeness evaluation, and potential target prediction to advance drug discovery. Through this paradigm, we unveil modulating the ABCA1/ABCG1-mediated cholesterol-mitophagy pathway as a promising anti-AD strategy, with a novel drug candidate JGX-1 identified.
Alzheimer’s disease (AD), Parkinson’s disease (PD), and Amyotrophic Lateral Sclerosis (ALS) are neurodegenerative diseases characterized by dysfunction of the endosomal-lysosomal system (ELS). Four shared neurodegenerative mechanisms across ALS, PD and AD are regulated by the ELS, namely proteostasis and related protein misfolding, mitochondrial function, neurotransmission and neuroinflammation. These mechanisms are interconnected, contributing to neurodegeneration in a “snowball” manner. The retromer, a multimeric, evolutionarily conserved protein complex involved in intracellular protein trafficking, is at the crossroad of these neurodegenerative processes. This narrative review focuses on exploring the retromer structure, function as a master regulator of the ELS, and how this impacts proteostasis, mitochondrial biogenesis and homeostasis, neurotransmission and neuroinflammation across neurodegenerative diseases. We explore how alterations in retromer function can play an important role in neurodegeneration and discuss the impact of genetic and pharmacological manipulations of VPS35, one of the main retromer subunits. In vitro and in vivo studies have identified that the retromer enhances the activity of protein degradation pathways via the ELS, namely macroautophagy, chaperone-mediated autophagy, and the ELS itself, with concomitant reduction in misfolded protein levels. Also, in some model systems, when the retromer role is enhanced or restored, mitochondrial function is rescued, dysfunctional neurotransmission is restored, and the damaging effects of neuroinflammation are dampened. Lastly, we highlight the role of a novel pharmacological class of agents that enhance retromer function as a strategy for potentially slowing the progression of these neurodegenerative diseases in in vivo models of PD and ALS. We discuss the challenges in targeting the retromer, current limitations and potential off-target effects of retromer enhancement. Overall, the retromer regulates shared mechanisms across neurodegenerative diseases and retromer enhancers could represent a novel disease-modifying strategy in AD, PD and ALS.
