Phosphoproteome modifications and cortical circuit dysfunction are linked to the early-stage progression of alpha-synuclein aggregation.
Dutta, S., Hensel, J., Scott, A., Mohallem, R., Rossitto, L.-A. M., Khan, H. F., Diehl, L. A., Johnson, T., et al.
neuroscience
Quick verdict
Multi-omics study claims aSyn PFF seeding drives cortical phosphoproteomic change and circuit dysfunction with novel pERK+GVB-like structures; credible but underpowered validation, permissive q<0.1 and male-only cohorts temper it.
Summary
This preprint asks whether alpha-synuclein (aSyn) preformed fibril (PFF) seeding alters cortical molecular and circuit function before neurodegeneration. Rats received bilateral intrastriatal PFF or monomer; cortical tissue was analyzed 3 months later by LC-MS/MS proteomics, phosphoproteomics (PolyMAC enrichment), and lipidomics. Global proteomics and lipidomics were largely unchanged, but 220 phosphosites (161 proteins) changed at q<0.1, with GO enrichment for synaptic transmission and cytoskeletal organization; convergent phosphoproteomic changes appeared in mice injected intrastriatally or intracortically (526 and 296 sites). Motif and RoKAI analyses implicated CK2, PKA, and ERK1/2. In vivo recordings showed increased firing and 5-20 Hz spike-spike coherence in mouse sensorimotor cortex. Notably, pERK1/2-positive granulovacuolar body-like structures, colocalizing CK1δ, CHMP2B, and pTau, appeared selectively in aggregate-bearing neurons across timepoints, regions, and primary neurons within 6 days. Key limitations: the independent pERK Western blot validation missed significance, global proteomics was acknowledged as underpowered, only male animals were used, phosphoproteomics used the permissive q<0.1 threshold, and analysis code was not released despite PRIDE/PURR data deposition.
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Assessment at a glance
4
risk flags identified
● high 0
● medium 2
● low 2
4 strengths · 5 weaknesses · 5 author questions
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Key claims under review
- Intrastriatal aSyn PFF injection induces sensorimotor cortex phosphoproteomic — but not global proteomic or lipidomic — changes at 3 months, before overt neurodegeneration.
- The altered phosphosites are enriched in synaptic and cytoskeletal pathways and predict activation of CK2, PKA, and the ERK1/2/MAPK cascade.
- PFF-treated mice show cortical circuit dysfunction: elevated neuronal firing rates and enhanced 5–20 Hz spike-spike coherence in sensorimotor cortex.
- pERK1/2-positive granulovacuolar body-like structures form selectively in aggregate-bearing neurons across timepoints, brain regions, and in primary neurons within 6 days, representing an early neuronal stress response to aSyn aggregation.
Strengths
Multi-modal, cross-species, dual-route design
Rat bilateral intrastriatal PFF plus mouse unilateral intrastriatal and intracortical PFF cohorts show convergent cortical phosphoproteomic signatures (220 sites in rat; 526 and 296 in mice at q<0.1), with correlated hit lists across mouse injection routes (Supplementary Fig. 6A) — supporting that effects follow intraneuronal aggregation rather than injection route.
Novel and well-triangulated pERK1/2+ GVB-like observation
Extranuclear pERK1/2 puncta restricted to pS129-aSyn aggregate-bearing neurons, colocalized with canonical GVB markers (CK1δ, CHMP2B) and pTau (S202/pT205); observed at 1, 3, and 6 months, in amygdala/SNpc/striatum, in AraC-treated cultures (astrocyte-reduced), and as early as 6 days in primary neurons — extending GVB biology from tauopathy to synucleinopathy.
Molecular findings are linked to functional circuit readouts
Honest treatment of negative results
Weaknesses
Key ERK claim lacks statistically significant independent validation
Statistical power and threshold asymmetry
Male-only cohorts
Bulk-tissue omics with cell-type ambiguity
Analysis code not deposited
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Scope & Claims
This bioRxiv preprint (60 pp., not yet peer-reviewed) investigates early cortical consequences of seeded alpha-synuclein (aSyn) aggregation in rodent PFF models, before overt neurodegeneration. Rats received bilateral intrastriatal aSyn PFFs or monomer; mice received unilateral intrastriatal or intracortical injections. At 3 months, sensorimotor cortex was profiled by LC-MS/MS label-free proteomics, PolyMAC-enriched phosphoproteomics, and lipidomics, complemented by IHC, Western blots, Golgi-Cox spine analysis, and awake-head-fixed in vivo recordings (64-channel, Kilosort3). Central claims: (1) phosphoproteomic but not global proteomic/lipidomic cortical changes (220 rat phosphosites at q<0.1; 526/296 in mouse cohorts); (2) enrichment of synaptic-transmission and cytoskeletal GO terms; (3) predicted CK2, PKA, and ERK1/2-MAPK activation; (4) increased firing and 5–20 Hz spike-spike coherence in mouse sensorimotor cortex; (5) pERK1/2-positive GVB-like structures selectively in aggregate-bearing neurons — the most novel result.
The remaining sections cover Methodology Assessment, Statistical Evidence, Results & Reproducibility, Limitations & Risks, and Verdict & Recommendations.
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Frequently asked questions
What did this study find in the cortex 3 months after alpha-synuclein PFF injection?
Rats and mice injected with alpha-synuclein preformed fibrils (PFFs) showed significant changes in protein phosphorylation in the sensorimotor cortex 3 months after striatal or cortical seeding — affecting 220 phosphosites in rats and 526/296 in mice — while total protein levels and lipids were largely unchanged. The affected proteins were mostly synaptic and cytoskeletal, and electrophysiology showed increased neuronal firing and spike synchrony, indicating cortical circuit dysfunction before overt neurodegeneration.
What are granulovacuolar bodies and why does their link to alpha-synuclein matter?
Granulovacuolar bodies (GVBs) are dense, vacuolar structures associated with cellular stress and impaired lysosomal-autophagic function, previously studied mainly next to tau tangles in Alzheimer's disease. This paper reports pERK1/2-positive GVB-like structures in neurons containing alpha-synuclein aggregates — colocalizing with GVB markers CK1δ and CHMP2B and phosphorylated tau — suggesting GVB formation is a general neuronal stress response across proteinopathies, not a tau-specific one.
Which kinases did the phosphoproteomic analysis implicate?
Motif-enrichment and RoKAI kinase-inference analyses of the altered phosphosites predicted increased activity of casein kinase 2 (CK2), protein kinase A (PKA), and the ERK1/2 MAPK cascade (including MEK1/2 and p90RSK). Proline-directed motifs (GSK3/CDK5/p38) were also enriched but considered non-discriminative.
Are the data and code from this paper available?
Raw mass-spectrometry data are deposited in PRIDE (rat phosphoproteome PXD057490, mouse phosphoproteome PXD058091, rat global proteome PXD057499), and lipid-profiling data in the Purdue University Research Repository (PURR, doi:10.4231/BVVA-4393). No analysis code or scripts are reported as available, so exact re-analysis requires rebuilding the pipeline from the methods section.
About this review
This is an AI-generated preliminary review by Evolve.Pub, produced from the openly available text of the paper. It is not peer review and does not represent the authors' views. The canonical record of the paper is at the publisher link above.
- PDF text extraction is heavily truncated: the cell-type specificity results, electrophysiology results (Fig 4B-D narrative), parts of Experimental Methods (LC-MS/MS parameters, proteomics statistics, RNA-scope/transcriptomic comparison), Figure 4 captions, and Supplementary Materials are missing.
- Figures are not analyzable from the text (only captions and fragments); quantitative claims about PCA separation, volcano plots, and coherence plots cannot be independently verified.
- Omics cohort sample sizes are not visible in the extractable text; statistical assessment is based on thresholds and the authors' own power discussion.
- Preprint not peer-reviewed (bioRxiv, CC-BY 4.0).
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