ABSTRACT
Both the biogenesis and functions of osteoclasts and macrophages involves dynamic membrane traffic. We screened transcript levels for Rab family small GTPases related to osteoclasts and identified Rab38. Rab38 expression is upregulated during osteoclast differentiation and maturation. In osteoclasts, both Rab38 and its paralog, Rab32, colocalize to lysosome-related organelles (LROs). In macrophages, Rab32 is also found in LROs. LROs are part of the endocytic pathway but are distinct from lysosomes. After receptor activator of NF-κB ligand stimulation, LROs contain cathepsin K and tartrate-resistant acid phosphatase inside and help both proteins to accumulate around bone resorption pits. After osteoclast maturation, these enzymes are hardly found within LROs. In macrophages derived from Rab32 and Rab38 double knockout mice, both acidification and V-ATPase a3 localization were severely compromised. Both the double knockout macrophage and bafilomycin-treated wildtype macrophage show an increase in Lamp1-positive organelles, implying that biogenesis of lysosomes and LROs are related. These results indicate that Rab32 and Rab38 both play a crucial role in LRO biogenesis in macrophages and in osteoclasts.
ABSTRACT
Huangjiu (Chinese rice wine) is a popular and traditional alcoholic beverage in China; however, the consumption of Huangjiu readily results in hangover symptoms. The aim of this study was to identify the main components associated with behavioral inhibition, headache, and the relevant mechanisms by using a mice hangover model. The results of an open-field experiment revealed that the key biogenic amine associated with mice behavior was histamine, which inhibited the behavior activity of mice in a dose-dependent manner. Moreover, histamine treatment decreased the levels of serotonin (5-HT) and 5-hydroxyindole acetic acid. In addition, the levels of dopamine and nitric oxide, which are associated with migraine, increased in the brain tissue of mice. In addition, the expression of receptor genes of 5-HT, including Htr1a, Htr1f, and Htr2c, is essential in regulating various behaviors and mental activities. In conclusion, the present study demonstrated that histamine is a key component in Huangjiu, and it is related to hangover symptoms by affecting the level of 5-HT and its receptors.
ABSTRACT
Tartary buckwheat is used as an ingredient in flour and tea, as well as in traditional Chinese medicine for its antioxidant effects. Here, we found that an ethanol extract of tartary buckwheat (TBE) potently induced autophagy flux in HeLa cells by suppressing mTORC1 activity, as revealed by dephosphorylation of the mTORC1 substrates Ulk1, S6K, and 4EBP, as well as by the nuclear translocation of transcriptional factor EB. In addition to non-selective bulk autophagy, TBE also induced aggrephagy, which is defined as autophagy against aggregated proteins. Quercetin is a flavonol found at high levels in TBE. We showed that quercetin induced both non-selective bulk autophagy and aggrephagy. These effects were also observed in Huh-7 cells derived from hepatocytes. Thus, aggrephagy induction by TBE and quercetin may relieve alcoholic hepatitis, which is closely linked to the accumulation of protein aggregations called Mallory-Denk bodies.
ABSTRACT
Kampo, a system of traditional Japanese therapy utilizing mixtures of herbal medicine, is widely accepted in the Japanese medical system. Kampo originated from traditional Chinese medicine, and was gradually adopted into a Japanese style. Although its effects on a variety of diseases are appreciated, the underlying mechanisms remain mostly unclear. Using a quantitative tf-LC3 system, we conducted a high-throughput screen of 128 kinds of Kampo to evaluate the effects on autophagy. The results revealed a suppressive effect of Shigyakusan/TJ-35 on autophagic activity. TJ-35 specifically suppressed dephosphorylation of ULK1 and TFEB, among several TORC1 substrates, in response to nutrient deprivation. TFEB was dephosphorylated by calcineurin in a Ca2+ dependent manner. Cytosolic Ca2+ concentration was increased in response to nutrient starvation, and TJ-35 suppressed this increase. Thus, TJ-35 prevents the starvation-induced Ca2+ increase, thereby suppressing induction of autophagy.
Subject(s)
Autophagy/drug effects , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/drug effects , Drugs, Chinese Herbal/pharmacology , Animals , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Calcineurin/metabolism , Calcium/metabolism , Humans , Mechanistic Target of Rapamycin Complex 1/metabolism , Phosphorylation , Starvation/metabolismABSTRACT
In response to amino acid supply, mTORC1, a master regulator of cell growth, is recruited to the lysosome and activated by the small GTPase Rheb. However, the intracellular localization of Rheb is controversial. In this study, we showed that a significant portion of Rheb is localized on the Golgi but not on the lysosome. GFP-Rheb could activate mTORC1, even when forced to exclusively localize to the Golgi. Likewise, artificial recruitment of mTORC1 to the Golgi allowed its activation. Accordingly, the Golgi was in contact with the lysosome at an newly discovered area of the cell that we term the Golgi-lysosome contact site (GLCS). The number of GLCSs increased in response to amino acid supply, whereas GLCS perturbation suppressed mTORC1 activation. These results suggest that inter-organelle communication between the Golgi and lysosome is important for mTORC1 regulation and the Golgi-localized Rheb may activate mTORC1 at GLCSs.
Subject(s)
Golgi Apparatus/metabolism , Intracellular Membranes/metabolism , Lysosomes/metabolism , Mechanistic Target of Rapamycin Complex 1/metabolism , Ras Homolog Enriched in Brain Protein/metabolism , Amino Acids/pharmacology , Golgi Apparatus/drug effects , Green Fluorescent Proteins/metabolism , HEK293 Cells , HeLa Cells , Humans , Intracellular Membranes/drug effects , Lysosomes/drug effects , Protein Transport/drug effectsABSTRACT
Autophagy is an intracellular degradation pathway conserved in eukaryotes. Among core autophagy-related (Atg) proteins, mammalian Atg9A is the sole multi-spanning transmembrane protein, and both of its N- and C-terminal domains are exposed to the cytoplasm. It is known that Atg9A travels through the trans-Golgi network (TGN) and the endosomal system under nutrient-rich conditions, and transiently localizes to the autophagosome upon autophagy induction. However, the significance of Atg9A trafficking for autophagosome formation remains elusive. Here, we identified sorting motifs in the N-terminal cytosolic stretch of Atg9A that interact with the adaptor protein AP-2. Atg9A with mutations in the sorting motifs could not execute autophagy and was abnormally accumulated at the recycling endosomes. The combination of defects in autophagy and Atg9A accumulation in the recycling endosomes was also found upon the knockdown of TRAPPC8, a specific subunit of the TRAPPIII complex. These results show directly that the trafficking of Atg9A through the recycling endosomes is an essential step for autophagosome formation.
Subject(s)
Autophagosomes/metabolism , Autophagy-Related Proteins/metabolism , Endocytosis , Endosomes/metabolism , Membrane Proteins/metabolism , Vesicular Transport Proteins/metabolism , Adaptor Protein Complex 2/metabolism , Amino Acid Motifs , Animals , Autophagy , Autophagy-Related Proteins/chemistry , Gene Knockdown Techniques , HeLa Cells , Humans , Membrane Proteins/chemistry , Mice, Knockout , Models, Biological , Protein Transport , Salmonella/metabolism , Structure-Activity Relationship , Tyrosine/metabolism , Vesicular Transport Proteins/chemistry , trans-Golgi Network/metabolismABSTRACT
Macroautophagy is a major intracellular degradation system. We previously reported that overexpression of phosphatase-deficient MTMR3, a member of the myotubularin phosphatidylinositol (PI) 3-phosphatase family, leads to induction of autophagy. In this study, we found that MTMR3 interacted with mTORC1, an evolutionarily conserved serine/threonine kinase complex, which regulates cell growth and autophagy in response to environmental stimuli. Furthermore, overexpression of MTMR3 inhibited mTORC1 activity. The N-terminal half of MTMR3, including the PH-G and phosphatase domains, was necessary and sufficient for these effects. Phosphatase-deficient MTMR3 provided more robust suppression of mTORC1 activity than wild-type MTMR3. Furthermore, phosphatase-deficient full length MTMR3 and the phosphatase domain alone were localized to the Golgi. These results suggest a new regulatory mechanism of mTORC1 in association with PI3P.
Subject(s)
Adaptor Proteins, Signal Transducing/antagonists & inhibitors , Multiprotein Complexes/antagonists & inhibitors , Protein Tyrosine Phosphatases, Non-Receptor/metabolism , TOR Serine-Threonine Kinases/antagonists & inhibitors , Adaptor Proteins, Signal Transducing/chemistry , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Amino Acid Substitution , Animals , Autophagy/drug effects , Catalytic Domain , Cells, Cultured , Embryo, Mammalian/cytology , Enzyme Activation/drug effects , Gene Deletion , HEK293 Cells , Humans , Mechanistic Target of Rapamycin Complex 1 , Mice , Multiprotein Complexes/chemistry , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Mutation , Peptide Fragments/chemistry , Peptide Fragments/genetics , Peptide Fragments/metabolism , Protein Interaction Domains and Motifs , Protein Kinase Inhibitors/pharmacology , Protein Transport/drug effects , Protein Tyrosine Phosphatases, Non-Receptor/antagonists & inhibitors , Protein Tyrosine Phosphatases, Non-Receptor/chemistry , Protein Tyrosine Phosphatases, Non-Receptor/genetics , RNA Interference , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/metabolism , Regulatory-Associated Protein of mTOR , TOR Serine-Threonine Kinases/chemistry , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolism , mTOR Associated Protein, LST8 HomologABSTRACT
The aim of this study was to investigate the involvement of the RhoA/Rho kinase (ROCK) signaling pathway in the progression of ADR-induced heart failure. Rats were administered captopril or fasudil over a period of 6 days, and the ADR was injected intraperitoneally on day 4. Similar to the effect of captopril, fasudil treatment significantly protected against ADR-induced hemodynamic, histopathologic and ultra-structural changes and decreased plasma lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) in a dose-dependent manner in the left ventricle of the heart. While ADR treatment induced ROCKI mRNA expression, fasudil significantly and dose-dependently reduced the incidence of apoptosis and the ratio of bax/bcl-2 protein expression. Moreover, a dose-related decrease in c-jun mRNA expression and an increase in c-FLIP (L) expression were observed in the fasudil groups. Fasudil also downregulated NF-κB activity in a dose-dependent manner. These data indicated that the RhoA/ROCK signaling pathway plays an important role in the progression of heart failure induced by ADR, while fasudil increased resistance to cardiac cell injury. The mechanisms of fasudil-mediated protection against ADR-induced apoptosis may be related to higher c-FLIP (L) and bcl-2 expression, lower c-jun expression and inhibition of NF-κB activation in the heart.
