α-synuclein accumulation into dopaminergic neurons is a pathological hallmark of Parkinson’s disease. We previously demonstrated that fatty acid-binding protein 3 (FABP3) is critical for α-synuclein uptake and propagation to accumulate in dopaminergic neurons. FABP3 is abundant in dopaminergic neurons and interacts with dopamine D2 receptors, specifically the long type (D2L). Here, we investigated the importance of dopamine D2L receptors in the uptake of α-synuclein monomers and their fibrils. We employed mesencephalic neurons derived from dopamine D2L−/−, dopamine D2 receptor null (D2 null), FABP3−/−, and wild type C57BL6 mice, and analyzed the uptake ability of fluorescence-conjugated α-synuclein monomers and fibrils. We found that D2L receptors are co-localized with FABP3. Immunocytochemistry revealed that TH+ D2L−/− or D2 null neurons do not take up α-synuclein monomers. The deletion of α-synuclein C-terminus completely abolished the uptake to dopamine neurons. Likewise, dynasore, a dynamin inhibitor, and caveolin-1 knockdown also abolished the uptake. D2L and FABP3 were also critical for α-synuclein fibrils uptake. D2L and accumulated α-synuclein fibrils were well co-localized. These data indicate that dopamine D2L with a caveola structure coupled with FABP3 is critical for α-synuclein uptake by dopaminergic neurons, suggesting a novel pathogenic mechanism of synucleinopathies, including Parkinson’s disease.

Stroke is among the leading causes of death and disability worldwide. However, despite long-term research yielding numerous candidate neuroprotective drugs, there remains a lack of effective neuroprotective therapies for ischemic stroke patients. Among the factors contributing to this deficiency could be that single-target therapy is insufficient in addressing the complex and extensive mechanistic basis of ischemic brain injury. In this context, lipids serve as an essential component of multiple biological processes and play important roles in the pathogenesis of numerous common neurological diseases. Moreover, in recent years, fatty acid-binding proteins (FABPs), a family of lipid chaperone proteins, have been discovered to be involved in the onset or development of several neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease. However, comparatively little attention has focused on the roles played by FABPs in ischemic stroke. We have recently demonstrated that neural tissue-associated FABPs are involved in the pathological mechanism of ischemic brain injury in mice. Here, we review the literature published in the past decade that has reported on the associations between FABPs and ischemia and summarize the relevant regulatory mechanisms of FABPs implicated in ischemic injury. We also propose candidate FABPs that could serve as potential therapeutic targets for ischemic stroke.

Multiple system atrophy (MSA) is a neurodegenerative disease characterised by the accumulation of misfolded α-synuclein (αSyn) and myelin disruption. However, the mechanism underlying αSyn accumulation in MSA brains remains unclear. Here, we aimed to identify epsin-2 as a potential regulator of αSyn propagation in MSA brains. In the MSA mouse model, PLP-hαSyn mice, and FABP7/αSyn hetero-aggregate-injected mice, we initially discovered that fatty acid-binding protein 7 (FABP7) is related to MSA development and forms hetero-aggregates with αSyn, which exhibit stronger toxicity than αSyn aggregates. Moreover, the injected FABP7/αSyn hetero-aggregates in mice selectively accumulated only in oligodendrocytes and Purkinje neurons, causing cerebellar dysfunction. Furthermore, bioinformatic analyses of whole blood from MSA patients and FABP7 knock-down mice revealed that epsin-2, a protein expressed in both oligodendrocytes and Purkinje cells, could potentially regulate FABP7/αSyn hetero-aggregate propagation via clathrin-dependent endocytosis. Lastly, AAV5-dependent epsin-2 knock-down mice exhibited decreased levels of αSyn aggregate accumulation in Purkinje neurons and oligodendrocytes, as well as improved myelin levels and Purkinje neuron function in the cerebellum and motor performance. These findings suggest that epsin-2 plays a significant role in αSyn accumulation in MSA, and we propose epsin-2 as a novel therapeutic target for MSA.

Aims We previously found that a decoy peptide derived from the C‐terminal sequence of α‐Synuclein (αSyn) prevents cytotoxic αSyn aggregation caused by fatty acid‐binding protein 3 (FABP3) in vitro. In this study, we continued to utilize αSyn‐derived peptides to further validate their effects on αSyn neurotoxicity and behavioral impairments in αSyn preformed fibrils (PFFs)‐injected mouse model of Parkinson's disease (PD). Methods Mice were injected with αSyn PFFs in the bilateral olfactory bulb (OB) and then were subjected to behavioral analysis at 2‐week intervals post‐injection. Peptides nasal administration was initiated one week after injection. Changes in phosphorylation of αSyn and neuronal damage in the OB were measured using immunostaining at week 4. The effect of peptides on the interaction between αSyn and FABP3 was examined using co‐immunoprecipitation. Results αSyn PFF‐injected mice showed significant memory loss but no motor function impairment. Long‐term nasal treatment with peptides effectively prevented memory impairment. In peptide‐treated αSyn PFF‐injected mice, the peptides entered the OB smoothly through the nasal cavity and were mainly concentrated in neurons in the mitral cell layer, significantly suppressing the excessive phosphorylation of αSyn and reducing the formation of αSyn‐FABP3 oligomers, thereby preventing neuronal death. The addition of peptides also blocked the interaction of αSyn and FABP3 at the recombinant protein level, and its effect was strongest at molar concentrations comparable to those of αSyn and FABP3. Conclusions Our findings suggest that the αSyn decoy peptide represents a novel therapeutic approach for reducing the accumulation of toxic αSyn‐FABP3 oligomers in the brain, thereby preventing the progression of synucleinopathies.

Accumulation of α-synuclein protein into dopaminergic neurons is a pathological hallmark of Parkinson's disease. We previously demonstrated that fatty acid-binding protein 3 (FABP3) is critical for α-synuclein uptake into dopaminergic neurons and its propagation. FABP3 is abundant in dopaminergic neurons and interacts with the dopamine D2 receptor largely distributed in caveolae. In this study, we newly investigated the significance of caveolae formation in the uptake process of α-synuclein, coupled with FABP3. To disclose this issue, we employed mesencephalic neurons derived from dopamine D2-null knockout (D2-null) and FABP3 knockout (FABP3 -/-) as well as wild type C57BL6 mice, and treated with dynasore, a dynamin inhibitor, or caveolin-1 siRNA, and analyzed the ability of the uptake of fluorescence-conjugated α-synuclein monomer and fibrils. Our immunocytochemistry revealed that D2 receptors are co-localized with FABP3. Importantly, TH + D2-null neurons did not take up αsynuclein monomers. Moreover, exposure to dynasore, caveolin-1 knockdown, and the deletion of α-synuclein Cterminus abolished the uptake. D2 receptors and FABP3 were also essential for the uptake of α-synuclein fibrils. Intriguingly, D2 receptors and accumulated α-synuclein fibrils were well co-localized. These data indicate that caveolae formation with the D2 receptors coupled with FABP3 is critical for the uptake of α-synuclein via its Cterminus in dopaminergic neurons, suggesting a novel pathogenic mechanism of synucleinopathies including Parkinson's disease.