Microglial Melatonin Receptor 1 Degrades Pathological Alpha-Synuclein Through Activating LC3-Associated Phagocytosis In Vitro

Abstract

Aims

Parkinson's disease (PD) is characterized by the formation of Lewy bodies (LBs), primarily constituted of α-synuclein (α-Syn). Microglial cells exhibit specific reactivity toward misfolded proteins such as α-Syn. However, the exact clearance mechanism and related molecular targets remain elusive.

Methods

BV2 cells, primary microglia from wild-type and MT1 knockout mice, and primary cortical neurons were utilized as experimental models. The study investigated relevant mechanisms by modulating microglial MT1 expression through small RNA interference (RNAi) and lentiviral overexpression techniques. Furthermore, pathological aggregation of α-Syn was induced using pre-formed fibrils (PFF) α-Syn. Co-immunoprecipitation, immunofluorescence, Western blot (WB), and quantitative real-time PCR were used to elucidate the mechanisms of molecular regulation.

Results

In this study, we elucidated the regulatory role of the melatonin receptor 1 (MT1) in the microglial phagocytic process. Following MT1 knockout, the ability of microglial cells to engulf latex beads and zymosan particles decreased, subsequently affecting the phagocytic degradation of fibrillar α-Syn by microglial cells. Furthermore, the loss of MT1 receptors in microglial cells exacerbates the aggregation of α-Syn in neurons induced by pre-formed fibrils (PFF) α-Syn. Mechanistically, MT1 influences the phagocytic function of microglial cells by regulating the Rubicon-dependent LC3-associated phagocytosis (LAP) pathway.

Conclusion

Taken together, the results suggest the neuroprotective function of microglial cells in clearing α-Syn through MT1-mediated LAP, highlighting the potential key role of MT1 in pathogenic mechanisms associated with α-Syn.