Corynoxine B targets at HMGB1/2 to enhance autophagy for α-synuclein clearance in fly and rodent models of Parkinson's disease

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.

Polyglutamine-expanded ataxin-3 is degraded by autophagy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the role of autophagy on the pathogenesis of spinocerebellar ataxia 3/Machado-Joseph disease (SCA3/MJD).</p><p><b>METHODS</b>HEK293 cells expressing polyglutamine-expanded ataxin-3 were used as cell model for SCA3/MJD. The level of polyglutamine-expanded ataxin-3 was detected after cells were treated with different inhibitors or inducer of autophagy.</p><p><b>RESULTS</b>Inhibition of autophagy increased aggregate formation and cell death in HEK293 cells expressing mutated ataxin-3, and vice versa.</p><p><b>CONCLUSION</b>The data suggested that autophagy is involved in the degradation of mutant ataxin-3, resulting in a decrease in the proportions of aggregate-containing cells and cell death in HEK293 cells expressing polyglutamine-expanded ataxin-3. It is possible that autophagy may be applied as a potential therapeutic approach for SCA3/MJD.</p>

Screening of LRRK2 interactants by yeast 2-hybrid analysis / 中南大学学报(医学版)

Objective To isolate and identify the potential binding partners of LRRK2,a gene linked to both dominant familial form and sporadic form of Parkinson's disease,thus to further our knowledge of its function.Methods We used a sequence containing full-length of COR domain and part of ROC and MAPKKK domain as bait.The bait amplified by polymerase chain reaction(PCR) was then cloned into a yeast expression plasmid pGBKT7.After being sequenced and analyzed,pGBKT7-bait was transformed into the yeast strain AH109.Western blot was performed to confirm the expression of pGBKT7-bait in AH109 yeast strain.Then human fetal brain cDNA library was trarnsformed into that yeast strain.which could express pGBKT7-bait fusion protein.The yeast strain which contained pGBKT7-bait and human fetal brain cDNA library was plated on quadruple dropout medium (SD/-Trp/-Leu/-His/-Ade)containing X-a-gal.We retested these positive colonies using 2 independent yeast strains AH109 contained pGBKT7-bait or pGBKT7,respectively.At last,these plasmids isolated from these true positive colonies were analyzed by bioinformatics.Results We obtained 9 true positive colonies,these colonies were sequenced, and we performed sequence Blast in GenBank.Three colonies of the 9 positive colonies were not in open reading-frames.Among other 6 colonies,there were known proteins including spermatid perinuclear RNA-binding protein(STRBP)and BCL2-associated athanogene 5 isoform b(BAG5),as well as unknown proteins including tyrosine phosphatase non-receptor type(PTPN23),1(3)mbt-like 3 isoform b(L3 MBTL3),RALY RNA binding protein-like isoform 1(RALYL),and Homo sapiens mRNA for KIAA1783 protein,partial cds(KIAA 1783).Conclusion True positive colonies of LRRK2 are successfully obtained by the yeast 2-hybrid.Our screened proteins may provide a new research clue for revealing biological functions of LRRK2,pathogenesis of Parkinson's disease,and other neurodegerations.