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
<p><b>OBJECTIVE</b>To explore the molecular mechanism of miR-124 suppressing the proliferation and invasion of gastric cancer cells.</p><p><b>METHODS</b>SPHK1 3'UTR-luciferase vector was constructed and luciferase reporter gene assay was employed to examine the effect of miR-124 on luciferase activity. Human gastric cancer MGC-803 cells were transfected with miR-124 mimics, and then Western blot was performed to detect the expression of SPHK1 protein.</p><p><b>RESULTS</b>Luciferase reporter vector system confirmed that SPHK1 was a target gene of miR-124. Western blot showed that the expression of SPHK1 protein was inhibited by miR-124. After transfection of miR-124 mimics or SPHK1 siRNA for 12 h, 24 h and 48 h, respectively, MTT assay showed that the A values of the three groups were significantly different (P < 0.05), and it was in a time-dependent manner. After transfection of miR-124 mimics or SPHK1 siRNA for 24 h, transwell invasion assay showed that the number of transmembrane cells was 54.6 ± 8.3 in the SPHK1 siRNA group and 47.8 ± 6.6 in the miR-124 mimics group, both were significantly lower than 100.6 ± 11.3 of the control group (P < 0.05), indicating that SPHK1 siRNA can slow down the invasion of MGC-803 cells.</p><p><b>CONCLUSION</b>miR-124 can suppress the cell proliferation and invasion by targeting SPHK1 in gastric carcinoma.</p>