This study aimed to explore the molecular mechanism of rubioncolin C(RuC) in inhibiting gastric cancer(GC). AGS and MGC803 cell lines were selected as cellular models. After treating the cells with RuC at different concentrations, the effects of RuC on the proliferation ability of GC cells were assessed using the CCK-8 method, real-time cellular analysis(RTCA), and colony formation assays. Transmission electron microscopy was used to observe subcellular structural changes. Immunofluorescence was applied to detect LC3 fluorescent foci. Acridine orange staining was used to evaluate the state of intracellular lysosomes. Western blot was employed to detect the expression of autophagy-related proteins LC3Ⅱ, P62, and lysosomal cathepsin D(CTSD). The SuperPred online tool was used to predict the target proteins that bound to RuC, and molecular docking analysis was conducted to identify the interaction sites between RuC and CTSD. The drug affinity responsive target stability(DARTS) assay was performed to detect the direct binding interaction between RuC and CTSD. The results showed that RuC significantly inhibited the proliferation and colony formation of GC cells at low concentrations, with 24-hour half-maximal inhibitory concentrations(IC_(50)) of 3.422 and 2.697 μmol·L~(-1) for AGS and MGC803 cells, respectively. After 24 hours of treatment with RuC at concentrations of 1, 2, and 3 μmol·L~(-1), the colony formation rates for AGS cells were 61.0%±1.5%, 28.0%±0.5%, and 18.2%±0.5%, respectively, while the rates for MGC803 cells were 56.0%±0.5%, 23.3%±1.0%, and 11.8%±1.0%, all of which were significantly reduced. Transmission electron microscopy revealed that RuC promoted an increase in autophagosome formation in GC cells. Immunofluorescence detection showed that LC3 fluorescent foci of GC cells increased with the increase in RuC dose. RuC up-regulated the expression of autophagy-related proteins LC3Ⅱ and P62 in GC cells. Acridine orange staining indicated that RuC altered the acidic environment of lysosomes. SuperPred online prediction identified CTSD as a potential target protein of RuC. Western blot analysis revealed that RuC induced the up-regulation of the inactive precursor of CTSD in GC cells. CTSD activity assays indicated that RuC reduced the activity of CTSD. Molecular docking simulations found that RuC bound to the substrate-binding region of CTSD, forming hydrogen bonds with the Tyr205 and Asp231 residues. Microscale thermophoresis and DARTS assays further confirmed that RuC directly bound to CTSD. In summary, RuC inhibits lysosomal activity by targeting and down-regulating the expression of CTSD, thereby inducing autophagosome accumulation in GC cells.
Humans ; Stomach Neoplasms/enzymology* ; Cathepsin D/chemistry* ; Cell Line, Tumor ; Molecular Docking Simulation ; Cell Proliferation/drug effects* ; Autophagosomes/metabolism* ; Autophagy/drug effects*

While several previous studies have indicated the link between periodontal disease (PD) and myocardial infarction (MI), the underlying mechanisms remain unclear. Autophagy, a cellular quality control process that is activated in several diseases, including heart failure, can be suppressed by Porphyromonas gingivalis (P.g.). However, it is uncertain whether autophagy impairment by periodontal pathogens stimulates the development of cardiac dysfunction after MI. Thus, this study aimed to investigate the relationship between PD and the development of MI while focusing on the role of autophagy. Neonatal rat cardiomyocytes (NRCMs) and MI model mice were inoculated with wild-type P.g. or gingipain-deficient P.g. to assess the effect of autophagy inhibition by P.g. Wild-type P.g.-inoculated NRCMs had lower cell viability than those inoculated with gingipain-deficient P.g. This study also revealed that gingipains can cleave vesicle-associated membrane protein 8 (VAMP8), a protein involved in lysosomal sensitive factor attachment protein receptors (SNAREs), at the 47th lysine residue, thereby inhibiting autophagy. Wild-type P.g.-inoculated MI model mice were more susceptible to cardiac rupture, with lower survival rates and autophagy activity than gingipain-deficient P.g.-inoculated MI model mice. After inoculating genetically modified MI model mice (VAMP8-K47A) with wild-type P.g., they exhibited significantly increased autophagy activation compared with the MI model mice inoculated with wild-type P.g., which suppressed cardiac rupture and enhanced overall survival rates. These findings suggest that gingipains, which are virulence factors of P.g., impair the infarcted myocardium by cleaving VAMP8 and disrupting autophagy. This study confirms the strong association between PD and MI and provides new insights into the potential role of autophagy in this relationship.
Mice ; Rats ; Animals ; Porphyromonas gingivalis ; Gingipain Cysteine Endopeptidases ; Autophagosomes ; Myocardium ; Periodontal Diseases ; Heart Rupture

Lipophagy, the selective engulfment of lipid droplets (LDs) by autophagosomes for lysosomal degradation, is critical to lipid and energy homeostasis. Here we show that the lipid transfer protein ORP8 is located on LDs and mediates the encapsulation of LDs by autophagosomal membranes. This function of ORP8 is independent of its lipid transporter activity and is achieved through direct interaction with phagophore-anchored LC3/GABARAPs. Upon lipophagy induction, ORP8 has increased localization on LDs and is phosphorylated by AMPK, thereby enhancing its affinity for LC3/GABARAPs. Deletion of ORP8 or interruption of ORP8-LC3/GABARAP interaction results in accumulation of LDs and increased intracellular triglyceride. Overexpression of ORP8 alleviates LD and triglyceride deposition in the liver of ob/ob mice, and Osbpl8-/- mice exhibit liver lipid clearance defects. Our results suggest that ORP8 is a lipophagy receptor that plays a key role in cellular lipid metabolism.
Animals ; Mice ; Lipid Droplets ; Autophagy ; Autophagosomes ; Homeostasis ; Triglycerides

Mutations in LR RK2 (Leucine rich repeat kinase 2) are a major cause of Parkinson's disease (PD). We and others reported recently that expression of the pathogenic gainof-function mutant form of LRRK2, LRRK2 G2019S, induces mitochondrial fission in neurons through DLP1. Here we provide evidence that expression of LRRK2 G2019S stimulates mitochondria loss or mitophagy. We have characterized several LRRK2 interacting proteins and found that LRRK2 interacts with ULK1 which plays an essential role in autophagy. Knockdown of either ULK1 or DLP1 expression with shRNAs suppresses LRRK2 G2019S expression-induced mitochondrial clearance, suggesting that LRRK2 G2019S expression induces mitochondrial fission through DLP1 followed by mitophagy via an ULK1 dependent pathway. In addition to ULK1, we found that LRRK2 interacts with the endogenous MKK4/7, JIP3 and coordinates with them in the activation of JNK signaling. Interestingly, LRRK2 G2019S-induced loss of mitochondria can also be suppressed by 3 different JNK inhibitors, implying the involvement of the JNK pathway in the pathogenic mechanism of mutated LRRK2. Thus our findings may provide an insight into the complicated pathogenesis of PD as well as some clues to the development of novel therapeutic strategies.
Amino Acid Substitution ; Autophagosomes ; metabolism ; pathology ; Autophagy-Related Protein-1 Homolog ; chemistry ; genetics ; metabolism ; GTP Phosphohydrolases ; antagonists & inhibitors ; genetics ; metabolism ; Gene Knockdown Techniques ; HeLa Cells ; Humans ; Intracellular Signaling Peptides and Proteins ; chemistry ; genetics ; metabolism ; Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 ; chemistry ; genetics ; metabolism ; MAP Kinase Signaling System ; Microtubule-Associated Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Mitochondrial Degradation ; genetics ; physiology ; Mitochondrial Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Mutant Proteins ; chemistry ; genetics ; metabolism ; Mutation ; Parkinson Disease ; genetics ; metabolism ; pathology ; Protein Interaction Domains and Motifs ; Recombinant Proteins ; chemistry ; genetics ; metabolism