👤 Kenta Shibahara

Apolipoprotein C-III (ApoC-III) amyloidosis is an extremely rare systemic amyloidosis previously reported only in humans and white lions. This report describes the first case of ApoC-III amyloidosis in an Asiatic lion (16-year-old male) that died with clinical manifestations of renal failure. Histopathological and ultrastructural examinations identified amyloid deposits predominantly at the renal corticomedullary junction. Mass spectrometry and immunohistochemistry identified ApoC-III as an amyloid precursor protein. Sequencing of the lion's APOC3 gene found no pathogenic mutations, although lion species have a unique M30V substitution compared with other Panthera species, which may predispose them to Apo-CIII amyloidosis. This first case of a non-white lion indicates that ApoC-III amyloidosis is not restricted to white lions. Show less

Macroautophagy/autophagy plays a critical role in the pathogenesis of various human diseases including neurodegenerative disorders such as Parkinson disease (PD) and Huntington disease (HD). Chemical autophagy inducers are expected to serve as disease-modifying agents by eliminating cytotoxic/damaged proteins. Although many autophagy inducers have been identified, their precise molecular mechanisms are not fully understood because of the complicated crosstalk among signaling pathways. To address this issue, we performed several chemical genomic analyses enabling us to comprehend the dominancy among the autophagy-associated pathways followed by an aggresome-clearance assay. In a first step, more than 400 target-established small molecules were assessed for their ability to activate autophagic flux in neuronal PC12D cells, and we identified 39 compounds as autophagy inducers. We then profiled the autophagy inducers by testing their effect on the induction of autophagy by 200 well-established signal transduction modulators. Our principal component analysis (PCA) and clustering analysis using a dataset of "autophagy profiles" revealed that two Food and Drug Administration (FDA)-approved drugs, memantine and clemastine, activate endoplasmic reticulum (ER) stress responses, which could lead to autophagy induction. We also confirmed that SMK-17, a recently identified autophagy inducer, induced autophagy via the PRKC/PKC-TFEB pathway, as had been predicted from PCA. Finally, we showed that almost all of the autophagy inducers tested in this present work significantly enhanced the clearance of the protein aggregates observed in cellular models of PD and HD. These results, with the combined approach, suggested that autophagy-activating small molecules may improve proteinopathies by eliminating nonfunctional protein aggregates. Show less

TOR (target of rapamycin) signaling regulates cell growth and division in response to environmental stimuli such as the availability of nutrients and various forms of stress. The vegetative growth of fission yeast cells, unlike other eukaryotic cells, is not inhibited by treatment with rapamycin. We found that certain mutations including pmc1Δ (Ca(2+)-ATPase), cps9-193 (small GTPase, Ryh1) and cps1-12 (1,3-β-D-glucan synthase, Bgs1) confer a rapamycin-sensitive phenotype to cells under salt stress with potassium chloride (>0.5 M). Cytometric analysis revealed that the mutant cells were unable to enter the mitotic cell cycle when treated with the drug under salt stress. Gene cloning and overexpression experiments revealed that the sensitivity to rapamycin was suppressed by the ectopic expression of tyrosine phosphatases, Pyp1 and Pyp2, which are negative regulators of Spc1/Sty1 mitogen-activated protein kinase (MAPK). The level of tyrosine phosphorylation on Spc1 was higher and sustained substantially longer in these mutants than in the wild type under salt stress. The hyperphosphorylation was significantly suppressed by overexpression of pyp1 (+) with concomitant resumption of the mutant cells' growth. In fission yeast, TOR signaling has been thought to stimulate the stress-response pathway, because mutations of TORC2 components such as Tor1, Sin1 and Ste20 result in similar sensitive phenotypes to environmental stress. The present study, however, strongly suggests that TOR signaling is required for the down-regulation of a hyperactivated Spc1 for reentry into the mitotic cell cycle. This finding may shed light on our understanding of a new stress-responsive mechanism in TOR signaling in higher organisms. Show less

Cytochrome P450 (CYP) 1A1 is involved in the metabolic activation of polycyclic aromatic hydrocarbons (PAHs) and is induced by several compounds, including PAHs. The induction of CYP1A1 mediated by the aryl hydrocarbon receptor (AhR) has been well investigated; however, little has been reported on the mechanisms of CYP1A1 induction mediated by factors other than AhR. In this study, we investigated the involvement of liver X receptor alpha (LXRα) in the induction of CYP1A1. TO-901317, an LXRα ligand, induced CYP1A1 mRNA in a dose-dependent fashion. Luciferase reporter assays using HepG2 cells showed that TO-901317 was capable of activating the promoter of the CYP1A1 gene and that a direct repeat 4 (DR4) motif located in a region from -452 to -467 was required for the induction of CYP1A1 through LXRα. Specific binding of LXRα to this DR4 motif was confirmed by gel shift and chromatin immunoprecipitation assays. Co-treatment of HepG2 cells with TO-901317 and 2,3,7,8-tetrachlorodibenzo-p-dioxin, a typical AhR ligand, caused the synergistic induction of CYP1A1 mRNA. Thus, we propose that the expression of CYP1A1 is regulated by LXRα as well as by AhR, suggesting that exposure to both LXRα and AhR ligands can result in the alteration of individual susceptibility to environmental carcinogens metabolically activated by CYP1A1. Show less