Translational Neurodegeneration

Post-translational modifications (PTMs) in APP and MAPT contribute to plaques and tangles in Alzheimers disease (AD). Yet broader proteome-wide PTMs in the AD brain are relatively unexplored. Therefore, this study highlights associations between PTMs, quantified by mass spectrometry in prefrontal cortex tissue, and Alzheimers disease neuropathology and cognition. Leveraging PTMs quantified from prefrontal cortices in 101 Rush Memory and Aging Project participants. We assessed associations with post-mortem amyloid-{beta} and tau burden, global cognition, and cognitive decline. First, APP and MAPT PTM associations were assessed on these outcomes given their known relevance in AD, followed by assessment of protein-wide effects of PTMs. Then, kinase enrichment analysis was performed on each outcome to assess which kinases might contribute to the results. We observed a novel association of APP-K687 acetylation, a known mutation hotspot driving pathology, with amyloid-{beta} load ({beta}=0.44, P=3.9e-8), while confirming known MAPT PTMs with tangle burden. Further, we identified 20+ novel PTMs associations with AD neuropathology, including ENO2-K256 ubiquitination ({beta}=0.353, P=1.13e-6), PSMD13-K31 ubiquitination ({beta}=0.568, P=1.34e-6), and PLXND1-K1826 ubiquitination ({beta}=0.577, P=7.08e-8) for tangle burden and SYP-K23 ubiquitination ({beta}=1.50, P=4.7e-8), TMEFF2-C80 cysteine oxidation ({beta}=1.64, P=1.1e-8), and STX1B-T121 phosphorylation ({beta}=0.898, P=3.3e-7) for amyloid-{beta} load. Further, kinase enrichment analyses highlight the complexity of disease-related proteome changes with some kinases like CDK5 showing expected over-enrichment (amyloid z=3.44, P=3.0e-4; tau z=4.98, P=3.3e-7) but others like PKC family kinases showing divergent enrichment between amyloid (z=8.98-11.55, P<1.0e-18) and tau (z=-2.83--3.88, P<0.006). This study provides an atlas of brain PTMs within crucial proteins like MAPT and APP and at the proteome-wide level, that impact AD neuropathology and clinical presentation. Further, we explored what kinases might be driving phosphorylation results, emphasizing the complex proteome changes which impact AD. In sum, these results highlight robust post-translational alterations in the AD brain and provide novel targets for future mechanistic studies.

Amyloid plaques are a hallmark neuropathological feature of Alzheimers disease (AD), composed of insoluble amyloid beta (A{beta}) peptide. A{beta} undergoes post-translational modifications that alter their biophysical properties, aggregation kinetics, and neurotoxicity, creating a heterogeneous pool of species that differentially affect AD pathogenesis. Pyroglutamate-modified A{beta} (pEA{beta}) is a particularly aggregation-prone and proteolytically resistant variant that preferentially accumulates within plaque cores, is implicated in early plaque seeding, and is a major target of emerging anti-amyloid immunotherapies. However, the molecular environment surrounding pEA{beta} versus unmodified A{beta} (pan-A{beta}) in the human hippocampus remains incompletely defined. Here, we used Biotinylation by Antibody Recognition (BAR), an in-situ proximity labeling approach, to map and compare the protein-protein interactions (proteomes) of pEA{beta} and pan-A{beta} in formalin-fixed postmortem human hippocampal tissue from pathologically confirmed AD cases and cognitively normal (CN) controls. Differential proteomic analysis identified 48 significantly enriched proteins in AD pEA{beta} captures, 28 in AD pan-A{beta} captures, and 15 in CN pan-A{beta} captures. Whereas no significant enrichment was detected in CN pEA{beta} captures, supporting pEA{beta} as a pathology-associated species. pEA{beta} in AD demonstrated the largest variant-specific signature with 31 unique proteins, pan-A{beta} showed 11 unique proteins in AD, and 14 unique proteins in CN, 16 proteins were shared between AD pEA{beta} and AD pan-A{beta}, with PCSK1N shared across AD pEA{beta}, and AD/CN pan-A{beta}. Pathway enrichment analysis revealed broader biological disruptions linked to pEA{beta}, including synaptogenesis signaling, clathrin-mediated endocytosis, mitochondrial division signaling, and neurotransmitter release. Shared pathways included SNARE signaling, glutamatergic receptor signaling, and netrin signaling. These findings demonstrate that pEA{beta} engages an expanded, variant-specific interactome in human AD hippocampus and designate intracellular trafficking, synaptic signaling, and mitochondrial pathways as network-level vulnerabilities relevant to pEA{beta} pathology in AD. Notably, comparison of CN versus AD pan-A{beta} further distinguished protein networks associated with physiological A{beta} engagement versus pathological pan-A{beta} deposition.

Basal forebrain cholinergic neurons regulate cortical activity and cognition and are vulnerable in Alzheimers disease (AD). However, the upstream circuits controlling projection-defined basal forebrain cholinergic populations remain incompletely understood. Here, we used projection-specific rabies-mediated monosynaptic tracing to map whole-brain inputs to medial prefrontal cortex (mPFC)-projecting cholinergic neurons in the nucleus basalis of Meynert (NBM) and horizontal limb of the diagonal band of Broca (HDB). mPFC-projecting NBM and HDB cholinergic neurons received broad but distinct input patterns. NBM cholinergic neurons received prominent striatal input, including input from D1-expressing medium spiny neurons, whereas HDB cholinergic neurons showed proportionally weaker striatal input and broader non-striatal contributions. Optogenetic electrophysiology confirmed that striatal inputs formed monosynaptic GABAergic inhibitory synapses onto NBM cholinergic neurons. This inhibitory transmission was weakened in 5xFAD mice, indicating impairment of a striatal-NBM inhibitory circuit in an AD mouse model. Together, these findings reveal subregion-specific input organization of mPFC-projecting basal forebrain cholinergic neurons and identify a vulnerable striatal-NBM circuit in AD. HighlightsO_LIWhole-brain rabies tracing reveals input organization of mPFC-projecting BF cholinergic neurons. C_LIO_LINBM and HDB cholinergic neurons projecting to mPFC show distinct monosynaptic input profiles. C_LIO_LIStriatal D1-MSNs are a major input source to mPFC-projecting NBM cholinergic neurons. C_LIO_LIStriatal-NBM inhibitory transmission is functionally impaired in 5xFAD mice. C_LI

-Synuclein nitration is a prominent post-translational modification in Parkinsons disease, but whether nitrated -synuclein merely reflects oxidative stress or actively contributes to pathology remains unclear. Here, we generated and characterized 6G6, an antibody selective for Tyr39-nitrated -synuclein, and tested whether targeting this modified -synuclein species affected pathology in different mouse models of -synuclein aggregation and spread. In two models of -synuclein overexpression targeting medullary vagal neurons, oxidative stress was induced by either exposure to the herbicide paraquat or transgenic heterozygous expression of the Gba1-L444P mutation. Both conditions were characterized by robust -synuclein spreading that was markedly counteracted by 6G6 administration. A third model consisted of an injection of -synuclein fibrils into the striatum of -synuclein-overexpressing mice. In this model, treatment with 6G6 protected against fibril-induced aggregate pathology and ensuing degeneration of nigral dopaminergic neurons. In a pilot human study, CSF levels of Tyr39-nitrated -synuclein were measured and found increased in Parkinson patients as compared to controls. These findings identify Tyr39-nitrated -synuclein as a pathogenic, therapeutically targetable -synuclein species linking oxidative/nitrative stress to PD pathological processes.

IntroductionDisturbances in one-carbon metabolism and homocysteine (Hcy) regulation have been implicated in Alzheimers disease (AD) and Parkinsons disease (PD), yet direct evidence from human brain tissue and the contribution of genetic variation remain limited. We investigated whether B-vitamin-related metabolic deficits and polymorphisms in one-carbon metabolism pathways contribute to cognitive impairment in AD and PD. MethodsWe quantitated metabolites related to B vitamins and one-carbon metabolism in post-mortem frontal cortex (n=136) and putamen (n=68) from clinically and neuropathologically characterized healthy controls, AD dementia (AD-D), PD with dementia (PD-D), PD with mild cognitive impairment (PD-MCI), and cognitively normal PD (PD-CN). Genotyping targeted variants related to one-carbon metabolism and B vitamins. Multivariable regression models controlled for demographic, clinical, metabolic, and tissue-handling covariates. ResultsAD-D and PD-D shared a convergent cortical signature of reduced biotin, pyridoxal-5-phosphate, thiamine monophosphate, pantothenic acid, and betaine. Elevated Hcy and reduced tetrahydrofolate were specific to AD-D and to PD-D during acute levodopa exposure. PD-MCI exhibited deficits in putamen resembling cortical dementia-associated changes. Self-reported B-vitamin supplementation attenuated several abnormalities, including complete normalization of levodopa-associated Hcy and folate disturbances in PD-D. Across subjects, multiple B vitamins showed strong associations with Hcy and betaine, indicating coordinated impairment of all three Hcy-metabolizing pathways. Genotyping analysis identified polymorphisms in MTRR, TYMS, MTR, NFE2L2, BHMT, and MTHFR that were differentially distributed across cognitive subgroups or associated with AD-related pathology scores. Composite genetic and metabolic burden scores were elevated in cognitively impaired groups but not in cognitively normal groups. ConclusionDementia in AD and PD is characterized by convergent B-vitamin deficiencies and genetic susceptibilities that disrupt Hcy metabolism. These findings provide a mechanistic explanation for levodopa-related Hcy accumulation in vulnerable PD subjects and identify B-vitamin supplementation as a potentially modifiable factor relevant to cognitive decline.

STRUCTURED ABSTRACTO_ST_ABSINTRODUCTIONC_ST_ABSA higher incidence of dementia, including Alzheimer s-like pathology, is observed in aged people living with HIV-1. However, mechanisms linking HIV-1 to Alzheimers disease (AD) pathology remain unclear, due to the lack of animal models that allow for concurrent study. METHODSWe created a novel APP knock-in (KI) AD mouse, NOG/APPKM670,671NL/IL-34 (hNAIL) that permits study of progressive brain HIV-1 replication. The mice harbor human microglia-like cells. Four-month-old CD34+ human cell reconstituted mice infected with the HIV-1ADA strain facilitated studies of HIV-1 replication on AD pathologies. RESULTSHIV-1 replication increased A{beta} levels and reduced synaptic and neuronal integrity. Spatial transcriptomics demonstrated distinct A{beta} and HIV-1 transcriptional patterns, whereas dual diseased combinations amplified AD pathology. Neurons showed highest transcriptional change, with genes linked to neuroinflammation, protein trafficking, and synaptic dysfunction. DISCUSSIONThe hNAIL mice enable interrogation of HIV-AD comorbidities, with a future potential for the development of novel therapeutic interventions.

INTRODUCTIONImproving the predictive validity of preclinical studies for Alzheimers disease (AD) requires rigorous evaluation of therapeutic efficacy, safety, and sex-specific responses in translationally relevant models. As amyloid-targeting monoclonal antibodies continue to advance clinically, there is an urgent need to define the molecular milieu that persists after amyloid is reduced and disease progression continues. Leveraging the NIA-funded MODEL-AD Preclinical Testing Core, we investigated the biochemical, functional, and multi-omic signatures associated with chronic administration of murine chimeric aducanumab (chAdu) in 5XFAD mice, including the contribution of IgG-mediated effects. METHODSMale and female 5XFAD mice were treated weekly with chAdu beginning at 8 months of age and compared to age-and sex-matched murine IgG2a{kappa} isotype (IgG) and saline controls. Plasma and brain pharmacokinetics, amyloid-beta (A{beta}), behavioral assessments, and treatment-emergent anti-drug antibodies (ADAs) were quantified. Post-treatment transcriptomic and proteomic analyses were performed to assess molecular pathways associated with chAdu and IgG exposure following 17-week treatment. RESULTSchAdu produced sex-dependent changes in A{beta}, including increased plasma A{beta}42:40 and reductions in brain A{beta} which were associated with mild behavioral impairments in the absence of improvements in cognitive function. IgG control treatment produced similar reductions, indicating biologically active IgG-mediated processes independent of A{beta}-targeted specificity. Treatment-emergent ADAs occurred in 10% of chAdu-treated mice and were associated with reduced drug exposure and efficacy. Multi-omics analyses confirmed sex-dependent and IgG-mediated effects at both the transcriptomic and proteome level revealing disease-associated genes and proteins not altered despite reductions in amyloid with treatment. DISCUSSIONThese findings demonstrate sex-dependent PK and pharmacodynamic responses to chAdu, identify biologically meaningful IgG-driven effects, and reveal molecular signatures that persist after amyloid reduction. This work provides biological insights into pathways that may remain insufficiently addressed following amyloid lowering; revealing novel targets for future drug discovery to prevent and treat disease.

Background: Alzheimer's disease (AD) is clinicopathologically heterogeneous. A proportion of patients living with AD present clinically at a younger onset of cognitive symptoms before 65 years old and/or non-amnestic clinical syndromes. Neuropathologically, corticolimbic distribution of neurofibrillary tangle pathology occurs on a continuum with some cases having greater cortical tau pathology relative to limbic regions and others with relatively restricted accumulation in limbic structures. These patterns of corticolimbic tangle distribution are associated with clinical presentation and age at onset. This study sought to examine protein expression differences across the spectrum of clinicopathologic heterogeneity using the NULISA targeted proteomics platform. Methods: A series of thirteen neuropathologically diagnosed AD cases from Mayo Clinic prospectively followed research studies were selected to reflect heterogeneity of clinical syndromes and corticolimbic distribution of tangle pathology. Frozen postmortem brain tissue samples were isolated from inferior parietal cortex and homogenized in RIPA buffer for analysis using Alamar Biosciences NULISA CNS disease 120 panel. Applying a conservative detection threshold of 75% level of detection for the novel application of NULISA in human brain, we evaluated levels of 69 of 129 protein targets across samples. We examined associations between age at onset cognitive symptoms and corticolimbic distribution of tangles (CLix) separately with individual protein targets using linear regression analysis. Results: AD cases with a younger age at onset had higher measured levels of ubiquitin, while older age was associated with higher levels of total tau, CRH, and NPTX2. Investigations of corticolimbic heterogeneity revealed AD cases with lower CLix score (i.e., cortical predominant distribution of tau) had higher measured p-tau181, p-tau231, ubiquitin, and p62. AD cases with higher CLix (i.e., relative cortical sparing) had higher levels of total tau, CRH, NPTX2, MDH1, and HBA1. Brain-derived total tau consistently showed a stronger association in both models. Conclusion: This work demonstrates the utility of postmortem proteomics for investigating biomarkers associated with AD clinicopathologic heterogeneity. We observed proteomic differences in synapse integrity, tau post-translational modification, and ubiquitination associated with age at symptomatic onset and corticolimbic distribution of tangle pathology.

IntroductionThe proteasome is a critical cellular degradative machinery impaired in late-stage Alzheimers disease (AD). However, the status and activity of the proteasome in early-stage sporadic AD (sAD) is unknown. MethodsA cellular model of human early-stage sAD was generated from sAD patient iPSC-derived cortical neurons by dual-SMAD inhibition. The iPSCs, neuroprogenitors, and cortical neurons were validated by the expressions of key markers. The level of total intraneuronal A{beta} was measured by ELISA. Composition and native proteolytic activities of the proteasome in control and sAD cortical neurons were measured using complementary fluorogenic probes. ResultsControl and sAD patients iPSCs expressed pluripotent markers OCT4, NANOG, and SSEA4 which induced into neuroprogenitors expressing NESTIN and PAX6. The neuroprogenitors terminally differentiated into cortical neurons expressing neuronal markers MAP2 and TUJ1, and cortical layer marker TBR1. The level of intraneuronal A{beta} in the sAD cortical neurons was significantly higher compared to control. Control and sAD cortical neurons expressed native 30S, 26S, and 20S proteasome assemblies with the sAD cortical neurons displaying higher 20S assemblies. Increased active 20S assemblies was associated with higher {beta}1, {beta}2, and {beta}5 proteolytic sites activities. DiscussionThe significant elevation in the proteolytic activities of the {beta}1, {beta}2, and {beta}5 subunits of 20S proteasome in sAD cortical neurons suggests that this may be a possible compensatory response to elevated intraneuronal A{beta}. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/734021v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1d8c382org.highwire.dtl.DTLVardef@b92e8org.highwire.dtl.DTLVardef@1d9c699org.highwire.dtl.DTLVardef@7d826d_HPS_FORMAT_FIGEXP M_FIG C_FIG

Alzheimers Disease (AD) remains the leading cause of dementia globally, yet the exact etiology is not well defined and effective treatments remain unavailable. Here, we report that deletion of the immune checkpoint receptor lymphocyte activation gene 3 (Lag3) in a familial AD mouse model, 5xFAD+, can rescue molecular, cellular and behavioral phenotypes of neurodegeneration. Specifically, we demonstrate that amyloidosis and microgliosis in the 5xFAD+ mice are significantly reduced by Lag3 deletion. Moreover, we show that Lag3 deletion attenuates deficits in neurodegeneration-related behavioral phenotypes in the 5xFAD+ mice. Transcriptional profiling reveals that Lag3 deletion suppresses aberrant overexpression of disease associated microglia (DAM) genes in 5xFAD+ microglia, effectively restoring homeostatic transcriptional programs. Finally, we observe reduced CD8+ T cell infiltration in the brain of 5xFAD+ animals after Lag3 deletion which likely mediates molecular, cellular and behavioral effects resulting from microglia DAM gene activation. Our results highlight a previously unrecognized role for Lag3 in AD as a critical regulator of microglia function and suggest Lag3 might be a viable target for novel AD therapeutic interventions. HighlightsO_LIImmune receptor Lag3 deletion ameliorates amyloidosis and microgliosis during AD C_LIO_LILag3 deletion attenuates deficits in neurodegeneration-related behavioral phenotypes C_LIO_LILag3 deletion reverses aberrant activation of DAM genes and restores microglia homeostasis C_LIO_LILag3 inhibition presents a viable approach for novel AD therapeutic interventions C_LI

Alzheimer's disease (AD) pathogenesis involves complex, multifactorial changes to the brain proteome that conventional unfractionated analyses may obscure. Proteins frequently occupy multiple subcellular compartments as spatial proteoforms, yet the contribution of aberrant protein localization to AD pathogenesis remains poorly understood. To address this, we fractionated post-mortem human hippocampi from 13 AD and 14 non-AD individuals into four subcellular fractions and quantified 6,123 proteins by TMT-LC-MS. Although 75% of proteins were detected in more than one fraction, 78% of significant AD-associated alterations were restricted to a single fraction, demonstrating that subcellular localization is a primary determinant of disease vulnerability. Discordant abundance patterns between fractions revealed retromer complex mislocalization, nuclear transport dysfunction, and insoluble protein accumulation, with the endosomal-lysosomal and protein folding pathways most consistently perturbed. To examine how these perturbations evolve with disease progression, we applied the QUAD strategy to measure protein degradation in two fractions of APPswePS1delta9 mouse cortex at 2, 5, and 12 months. Degradation rates diverged between fractions and genotypes in an age-dependent manner, and cross-dataset comparison identified six proteins altered at the earliest pre-pathological timepoint, implicating vesicle transport and proteostasis disruption as initiating features of AD. These findings establish spatial proteoforms as essential units of pathogenic analysis and reveal disease-relevant signals invisible to bulk tissue approaches.

Large-scale plasma proteomics can capture molecular changes across the Alzheimers disease (AD) continuum and provide insight into biological mechanisms associated with AD pathology. We analysed the Bio-Hermes cohort (n = 961), with participants enrolled across 17 sites in the United States from April 2021 to November 2022. Participants were stratified by clinical status and amyloid PET scan-based Core1 biomarker status (CN Core1-, CN Core1+, MCI Core1+, and AD dementia Core1+). We performed differential abundance analyses across biologically defined contrasts, clustered proteins into co-expression networks, and evaluated protein panels to distinguish participants with biologically defined AD from amyloid-negative cognitively normal controls. We also used Mendelian randomization (MR) to assess genetic evidence for potential causal relationships with AD risk. The biologically defined contrast, Core1+ vs. CN Core1-, identified 69 differentially abundant proteins. Across AD stages, eight core proteins were consistently dysregulated from preclinical through prodromal and dementia phases, and three additional proteins emerged at MCI Core1+ and remained altered in AD dementia Core1+. We identified 29 co-expression modules, six of which varied significantly across the AD continuum. Among differential abundance proteins, ACHE ranked highest for distinguishing biologically defined AD from CN Core1-. Stage-specific protein panels improved the discriminatory performance for MCI Core1+ (AUC = 0.850) and AD dementia Core1+ (AUC = 0.856). MR provided genetic evidence consistent with an association between plasma ACHE abundance and AD risk. Plasma proteomics delineated a stage-spanning core signature across the AD continuum. These findings nominate co-expression modules and candidate proteins for further validation in early detection and AD screening.

Synucleinopathies are a group of neurodegenerative disorders characterized by the accumulation of aggregated -synuclein (-syn), including Parkinson's disease, Dementia with Lewy Bodies, and Multiple System Atrophy. These diseases are marked by locomotor and non-motor impairments, as well as mitochondrial dysfunction and the loss of dopaminergic (DA) neurons. We have developed several anti--syn single-domain antibodies (sdAbs) and demonstrated the diagnostic imaging potential of two of them and the acute therapeutic benefit of one in clearing -syn in a mouse model. However, whether these sdAbs can suppress -syn-mediated neuronal loss and locomotor impairment in vivo remains unclear. We evaluated the therapeutic potential of five anti--syn sdAbs to clear pathological -syn in mouse neuronal culture and then demonstrated their in vivo efficacy in a Drosophila model of synucleinopathy. The sdAbs differed in their efficacy to lower levels of phospho-serine 129 -syn, prevent loss of DA neurons, alleviate mitochondrial dysfunction, improve motor function, and prolong survival in synucleinopathy flies. The most effective sdAb, 2H1, has not been reported before. It binds strongly to the aggregation prone region of -syn and robustly improves all these disease parameters. Additionally, that sdAb is associated with -syn in the fly neurons, as shown through proximity dependent turboID biotinylation assays. The sdAb-turboID also biotinylated -syn-associated proteins involved in synapse/vesicle trafficking pathways, pinpointing the location of their intracellular interaction. Our findings provide an insight into the therapeutic mechanism of action of these sdAbs and strongly support their clinical development.

Alzheimer's disease (AD) is classically defined by amyloid and tau pathology and is accompanied by broad disruptions in proteostasis. Heat shock proteins (HSPs) help maintain proteostasis, yet mitochondrial chaperone systems remain comparatively underexplored in AD. Hsp60 and Hsp10 form a mitochondrial chaperonin complex that folds dozens of AD-implicated mitochondrial proteins, but this client network has not been evaluated as an integrated proteostasis axis in AD. It remains unknown whether Hsp60/10 client proteins are selectively vulnerable across AD severity. We analyzed transcriptomic, proteomic, neuropathological, and cognitive data from the Religious Order Study and Memory and Aging Project (ROSMAP) to evaluate Hsp60/10 client proteins in AD. We compared Hsp60/10 clients with abundance-matched non-client mitochondrial proteins and tested differences across AD diagnostic groups and associations with Braak/tau burden, cognitive outcomes, and network centrality. These evidence layers were integrated into a candidate prioritization framework. Hsp60/10 client abundance declined more strongly at the protein level than at the RNA level in late-stage AD. Compared with abundance-matched non-client mitochondrial proteins, Hsp60/10 clients showed stronger late-stage protein abundance decline. Greater late-stage client decline was associated with higher Hsp60/10 network centrality, defining a selectively vulnerable client subnetwork. Lower client abundance was associated with greater Braak/tau burden and greater cognitive impairment. Integrated prioritization nominated mitochondrial translation and TCA/pyruvate/redox clients as high-priority candidates for mechanistic follow-up. Together, these findings identify an Hsp60/10 client-centered mitochondrial proteostasis axis spanning mitochondrial translation and TCA/pyruvate/redox metabolism that is associated with AD severity. These findings identify a novel potential axis warranting further investigation as a mechanistic link between mitochondrial dysfunction, proteostasis, and AD.

Parkinsons disease (PD) is characterized by progressive degeneration of nigrostriatal dopamine neurons and synucleinopathy, which is the accumulation of aggregated -synuclein (-syn). Increasing evidence implicates -syn-associated neuroinflammation as a contributor to PD pathogenesis; however, immune mechanisms linking synucleinopathy to neurodegeneration remain incompletely defined. Activation of the complement cascade occurs in PD and other neurodegenerative disorders, but most studies report complement activation after overt neurodegeneration, making it difficult to conclude if complement is directly activated by pathological -syn or secondarily following neurodegeneration. We used the rat -syn preformed fibril (PFF) mode, in vitro complement assays and human postmortem PD tissue to test whether pathological -syn directly activates complement prior to overt neurodegeneration. The -syn PFF model exhibits a protracted pathological time course and distinct temporal separation between peak -syn aggregation and nigrostriatal degeneration; thus we quantified complement expression, activation, and regulation during the aggregation phase. Synucleinopathy induced complement activation prior to nigrostriatal degeneration, including upregulation of components of both the classical (C1qa, C1r, C4b) and alternative (Cfd, Cfb) pathways, the anaphylatoxin (C3aR, C5aR) and phagocytic (CR3) complement receptors, and activation of complement C3. During early synucleinopathy, microglia upregulated C3 which significantly correlated with synucleinopathy burden across several brain regions, including the substantia nigra pars compacta (SNc) and cortex. Concurrently, complement regulatory proteins, including CD55, CD59, neuronal pentraxin-1 (Nptx1), and the neuronal pentraxin receptor were downregulated in the synucleinopathy-affected SNc. Importantly, increased levels of C1q and iC3b along with downregulation of CD55 and NPTX1 were also observed in human postmortem PD SNc, supporting the translational relevance of our findings. Mechanistically, we demonstrate that aggregated, but not monomeric, -syn directly binds C1q and activates the complement cascade in a C1q-dpendent manner. These data provide the first in vivo evidence that synucleinopathy triggers complement activation and dysregulation prior to neurodegeneration.

Parkinsons disease (PD) is a neurodegenerative disorder characterized by a prolonged prodromal stage that culminates in motor deficits. Current PD therapies primarily alleviate symptoms, underscoring the need for disease-modifying strategies. Glucagon-like peptide-1 (GLP-1) analogs showed early promise as candidate disease modifiers, but recent clinical results have been inconsistent, and their mechanism of action remains poorly defined. Here, we employed our SncaG51D/G51D knock-in mouse model to investigate the effects of subcutaneously administered GLP-1 analogs, semaglutide and lixisenatide. Both analogs reversed motor and non-motor deficits and reduced gliosis and detergent-insoluble -synuclein. Bulk and single-nuclei transcriptomics together with CellChat-based intercellular communication analysis revealed that GLP-1 analogs normalize early striatal mitochondrial and inflammatory dysregulation and restore neuregulin (NRG) and neurexin (NRXN) signaling networks to wild-type levels. Treatment was effective when initiated either before or shortly after symptom onset, defining an early therapeutic window for GLP-1 analog therapy in PD.

Obesity and diabetes are well-established risk factors for Alzheimers disease (AD), implicating metabolic dysfunction in AD pathogenesis. Sleeve gastrectomy (SG) is among the most effective metabolic interventions available, yet its impact on AD progression remains poorly understood. We hypothesized that SG performed early in life would improve metabolic health, attenuate AD pathology, and preserve cognition in a transgenic AD mouse model. Five-week-old female 3xTg-AD mice were preconditioned on a Western diet (WD) to induce obesity and glucose intolerance, then randomized to SG or sham surgery and maintained on either standard chow or continued WD for 12 months. Metabolic phenotyping, body composition, and cognitive assessments (Novel Object Recognition, Barnes Maze, Fear Conditioning) were performed longitudinally, with histological and molecular analysis of brain tissue at endpoint. Under chow-fed conditions, SG reduced adiposity, improved insulin sensitivity, and decreased cortical A{beta} plaque burden, accompanied by attenuated gliosis (GFAP, IBA1) and region-specific, insulin pathway-dependent modulation of autophagy. Under persistent WD, SG improved metabolic health, frailty, spatial cognition, and A{beta} pathology, again with corresponding perturbations in autophagy pathway activity. Across all groups, food intake did not differ significantly, indicating that these effects were not secondary to caloric restriction. Collectively, these data suggest that SG engages neuroprotective brain insulin signaling pathways, supporting metabolic surgery as a promising disease-modifying intervention for AD prevention in individuals with obesity.

Post-translational modifications critically regulate neurodegenerative disease progression. In Alzheimers disease (AD) and tauopathies, Tau hyperphosphorylation promotes aggregation and pathological spreading, whereas O-GlcNAcylation has emerged as a protective modification alongside its interplay with phosphorylation. However, the role of in vitro site-specific and global O-GlcNAcylation in Tau proteinopathy remains elusive. Here, using full-length Tau-441 (2N4R), we showed that O-GlcNAcylated Tau aggregated slowly, formed distinct aggregate morphology and exhibited reduced seeding capacity compared to wild-type (WT) Tau. Under phase-separated conditions, O-GlcNAcylated Tau formed oligomer like condensates. Mutation of the key O-GlcNAc sites reduced O-GlcNAc-transferase (OGT) mediated O-GlcNAcylation, cellular transmission and affected cross-talk with phosphorylation relative to WT. OGT overexpression alleviated WT-Tau toxicity in cells, and O-Tau fibrils were less toxic to primary cortical neurons compared to WT Tau fibrils. Finally, an in-house novel site-specific S422 O-GlcNAc-Tau antibody revealed reduced S422 O-GlcNAcylation in AD brain tissues, highlighting its protective role in AD pathogenesis.

Mitochondrial (MT) dysfunction is a key driver of ALS pathology. Without a healthy MT system, motor neurons (MN) function at sub-optimal levels and die. In addition, other effects of ALS, like axon/dendrite degeneration, may occur from a pathophysiological cascade spurred by MT dysfunction. A phenotypic screen identified Dipyridamole (DPM), an FDA-approved and safe drug, as having extraordinary effects on ALS patient induced pluripotent stem cell (iPSC)-derived MNs. The drug prevented MT fragmentation, loss of MT content, impaired MT bioenergetics, axon/dendrite degeneration, and premature MN death, extending neuronal survival by more than fivefold. Importantly, its efficacy extended across iPSC-derived neurons representing two different familial forms of ALS (C9orf72, TDP43) and Alzheimers disease (PSEN1), implying broad neuroprotection across ALS forms and other neurodegenerative diseases. DPM increased MT respiration and pyruvate uptake in a mechanism requiring the Mitochondrial Pyruvate Carrier (MPC), mechanistically explaining its biological activities. Thus, DPM is a promising drug to repurpose or refine for treating neurodegenerative diseases or other diseases that would benefit by augmenting pyruvate uptake into MT. TeaserDipyridamole, an FDA-approved drug, restores mitochondrial function and protects neurons in ALS and Alzheimers disease.

Adults with Down syndrome (DS) develop Alzheimer's disease (AD) brain pathology by age 40 due to triplication of the Amyloid Precursor Protein (APP) gene on chromosome 21. Inheritance of the apolipoprotein E-{epsilon}4 (APOE4) allele of the APOE gene on chromosome 19 remains the greatest genetic risk factor for AD in the typical population, yet its role in DS-associated AD (DS-AD) neuropathogenesis in people with DS is unclear. We generated human induced pluripotent stem cell (hiPSC)-derived neurons, astrocytes, and cerebral organoids (COs) using cells from people with DS and from euploid individuals. Aged DS COs were smaller than aged euploid COs and showed robust amyloid-{beta} neuropathology that was positively correlated with the levels of apoE expression. We then captured extracellular vesicles (EVs) from the conditioned media of COs and observed a decrease in the levels of secreted AD-related proteins, including amyloid, contained within the EVs and in the media from which the EVs were isolated. We also identified distinct neuronal and astrocytic gene expression signatures in DS COs relative to euploid COs, including a set of genes known to interact with both APOE and APP at the gene and/or protein levels. Lastly, we determined that, despite differences in the expression levels of the specific genes involved, several common pathways were upregulated in T21 hiPSC-derived neurons, astrocytes, and COs, including apoptosis, the endolysosome, and structural stabilization pathways. Taken together, our findings provide novel insights into molecular mechanisms that may contribute to DS-AD and indicate that apoE plays an important role in the disease process.