ABSTRACT
Parkinson's disease (PD) is the most common neurodegenerative movement disease. It is featured by abnormal alpha-synuclein (α-syn) aggregation in dopaminergic neurons in the substantia nigra. Macroautophagy (autophagy) is an evolutionarily conserved cellular process for degradation of cellular contents, including protein aggregates, to maintain cellular homeostasis. Corynoxine B (Cory B), a natural alkaloid isolated from Uncaria rhynchophylla (Miq.) Jacks., has been reported to promote the clearance of α-syn in cell models by inducing autophagy. However, the molecular mechanism by which Cory B induces autophagy is not known, and the α-syn-lowering activity of Cory B has not been verified in animal models. Here, we report that Cory B enhanced the activity of Beclin 1/VPS34 complex and increased autophagy by promoting the interaction between Beclin 1 and HMGB1/2. Depletion of HMGB1/2 impaired Cory B-induced autophagy. We showed for the first time that, similar to HMGB1, HMGB2 is also required for autophagy and depletion of HMGB2 decreased autophagy levels and phosphatidylinositol 3-kinase III activity both under basal and stimulated conditions. By applying cellular thermal shift assay, surface plasmon resonance, and molecular docking, we confirmed that Cory B directly binds to HMGB1/2 near the C106 site. Furthermore, in vivo studies with a wild-type α-syn transgenic drosophila model of PD and an A53T α-syn transgenic mouse model of PD, Cory B enhanced autophagy, promoted α-syn clearance and improved behavioral abnormalities. Taken together, the results of this study reveal that Cory B enhances phosphatidylinositol 3-kinase III activity/autophagy by binding to HMGB1/2 and that this enhancement is neuroprotective against PD.
ABSTRACT
As a cellular bulk degradation and survival mechanism, autophagy is implicated in diverse biological processes. Genome-wide association studies have revealed the link between autophagy gene polymorphisms and susceptibility of autoimmune diseases including systemic lupus erythematosus (SLE) and inflammatory bowel disease (IBD), indicating that autophagy dysregulation may be involved in the development of autoimmune diseases. A series of autophagy modulators have displayed protective effects on autoimmune disease models, highlighting the emerging role of autophagy modulators in treating autoimmune diseases. This review explores the roles of autophagy in the autoimmune diseases, with emphasis on four major autoimmune diseases [SLE, rheumatoid arthritis (RA), IBD, and experimental autoimmune encephalomyelitis (EAE)]. More importantly, the therapeutic potentials of small molecular autophagy modulators (including autophagy inducers and inhibitors) on autoimmune diseases are comprehensively analyzed.