Selective Neuronal Vulnerability to Alpha-Synuclein Pathology in Parkinson’s Disease: A Critical Review of Mechanistic Rationale and Biomarker Stratification

α-Synuclein burden amplification in Parkinson’s disease: a unified genetic, molecular, and cellular framework

Introduction Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized pathologically by the accumulation and propagation of α-synuclein (α-syn). Although α-syn aggregation is considered central to PD pathogenesis, increasing evidence suggests that α-syn abundance may be as important as its conformational state. Genetic studies have demonstrated an SNCA dosage effect, with gene duplication and triplication associated with progressively more severe familial PD phenotypes. Complementary evidence indicates that dysfunction of protein clearance pathways, particularly the autophagy–lysosome system, promotes intracellular α-syn accumulation and increases its neurotoxic potential. In this review, we propose α-syn multiplication as an integrative framework for interpreting PD pathogenesis. This concept extends beyond SNCA copy-number variation to encompass processes that increase the effective α-syn burden within neurons or across neural networks, including increased gene expression, impaired degradation, disrupted proteostasis, and pathological propagation. Methods We summarize α-syn structural dynamics and the concentration-dependent distribution of monomeric, oligomeric, and fibrillar species. We then review evidence from SNCA gene-dosage studies and examine the role of the autophagy–lysosome pathway in regulating α-syn homeostasis, with particular emphasis on recent experimental findings demonstrating that autophagy deficiency exacerbates α-syn accumulation and neurodegeneration in human α-syn bacterial artificial chromosome transgenic mice. Results Collectively, the available genetic, biochemical, and experimental evidence supports a model in which the balance between α-syn production and clearance influences disease progression alongside protein misfolding. The interaction between increased protein burden and impaired clearance capacity provides a unifying mechanism linking familial and sporadic forms of PD. Discussion We propose that α-syn multiplication offers an integrative framework for understanding PD pathogenesis, provides a quantitative perspective on disease heterogeneity, and highlights therapeutic opportunities aimed at reducing α-syn burden and restoring proteostatic balance.

Role of STX1A in Parkinson’s disease: evidence, mechanistic hypotheses, and translational perspectives

The biomarker and therapeutic potential of STX1A remains preliminary because diagnostic performance, disease specificity, longitudinal stability, and causal relevance have not been adequately validated and future studies using cell-type-specific STX1A manipulation, rescue experiments, electrophysiology, and multicenter longitudinal cohorts are required to define the biological and clinical significance of STX1A in PD.

Cognitive dysfunction in Parkinson's disease: Hippocampal vulnerability and redox-driven mechanisms.

Cognitive dysfunction is one of the most disabling non-motor manifestations of Parkinson's disease (PD), progressing from mild cognitive impairment to Parkinson's disease dementia. Although multiple pathological processes have been individually implicated, the mechanisms linking neurotransmitter deficits, proteinopathies, circuit vulnerability, and neurodegeneration remain insufficiently integrated. Here, we synthesize current evidence on the pathophysiology of cognitive impairment in PD, emphasizing the convergence of dopaminergic, cholinergic, noradrenergic and serotonergic dysfunction with α-synuclein, tau and amyloid-β pathology. We highlight the hippocampus – particularly the CA2 subregion – as a critical anatomical hub connecting synaptic dysfunction, memory impairment, and dementia progression. Accumulating evidence identifies oxidative stress and neuroinflammation as central drivers across these pathological domains. Among endogenous sources of reactive oxygen species, NADPH oxidases (NOX), especially Nox4, emerge as key regulators of redox imbalance, protein aggregation and glial–neuronal interactions. Increased Nox4 activity correlates with hippocampal damage and cognitive decline, whereas experimental inhibition of Nox4 preserves synaptic integrity and improves memory performance in preclinical models. By integrating molecular, cellular and systems-level findings, this review positions redox dysregulation – and NOX-dependent signaling in particular – as a unifying mechanism underlying cognitive decline in PD, and discusses emerging therapeutic strategies targeting redox pathways, highlighting NOX modulation as a promising approach to modify the course of Parkinson's disease-associated cognitive impairment.

From synaptic development to degeneration: a narrative review of small molecule strategies targeting alpha-synuclein in Parkinson’s disease

Mitochondrial resilience: a convergent framework for pathogenesis and neuroprotection in Parkinson’s disease

This integrated framework reframes PD as a disorder of impaired cellular maintenance rather than solely a consequence of late-stage degenerative processes, and provides a translational shift from mechanism-based biomarkers to early detection of mitochondrial failure and supports therapeutic strategies aimed at restoring mitochondrial function and resilience.

Neurons to Genes A Comprehensive Review of Parkinson’s Disease

The urgent need for reliable biomarkers, early diagnosis, and multidisciplinary disease-modifying strategies for future therapeutic interventions is highlighted, with particular emphasis on challenges associated with bench-to-bedside translation.