👤 Fumihiro Murakami

Numerous cytosolic DNA sensors (CDSs), which are very important for recognizing cytosolic dsDNA derived from intracellular viruses and bacteria, exist in mammals. However, teleost CDSs are poorly understood. In this study, four CDSs, including the cyclic GMP-AMP synthase (cGAS), Sm-like protein 14 homolog A (LSm14A), DEAH-box helicase (DHX) 9, and DHX36 genes were identified in Japanese medaka, Oryzias latipes, and their expression patterns were elucidated. The expression of these genes was upregulated in the intestines and kidney of CpG-ODN-stimulated medaka. The cGAS and LSm14A genes were significantly induced in the intestines, kidney, and spleen of formalin-killed Edwardsiella tarda-treated medaka; the DHX9 and DHX36 genes were not. cGAS gene expression was induced only in the intestines of live E. tarda-treated medaka. These results suggest that the transcription of four CDS genes of medaka responds to dsDNA stimulation, and cGAS is probably more important for the immune response against E. tarda infection. Show less

Cigarette smoke extract (CSE) contains many toxicants and may derange the physiological processes, such as cholesterol metabolism. We examined the impact of CSE on transcriptional regulation mediated peroxisome proliferator-activated receptors (PPARs) and its interaction with cofactors to elucidate differences in the molecular mechanism between CSE and other agonists of PPARs. We constructed several mutant PPARs (mPPARs) with amino acid substitution in the ligand-binding domain, which according to the molecular modeling, may affect the binding of agonists. In transient expression assays, each wild-type peroxisome proliferator-activated receptor (PPAR) mediated transcription stimulated by CSE was faintly yet significantly elevated compared to the control. The CSE-induced transcriptional activation was abolished in the H323A, H323Y, S342A, and H449A mPPARγs, although the activation elevated by pioglitazone was reserved. In the mPPARγ with Y473A and mPPARβ/δs with H286Y and Y436A, the pioglitazone-induced or L165041-activated transcriptional elevations were decreased and were lower than that of CSE-induced stimulation. These results suggested that CSE activated both mutant PPARs to be selectively different from those ligands. Mammalian two-hybrid assay illustrated that CSE could mildly recruit SRC1 or GRIP1 to the wild-type PPARγ. Representative ingredients, such as acrolein and crotonaldehyde present in CSE, could stimulate PPAR isoforms even at the toxicological concentrations and might possibly contribute to stimulatory effects. CSE mildly regulates the cholesterol metabolism-related genes, such as low density lipoprotein (LDL) receptor and Liver X receptor (LXR)β. In conclusion, these CSE effects the nuclear hormone receptors and their cofactors thereby disturbing metabolic phenomena. Therefore, CSE might be involved in cholesterol metabolism. Show less

Inherited GPI deficiencies (IGDs) are a subset of congenital disorders of glycosylation that are increasingly recognized as a result of advances in whole-exome sequencing (WES) and whole-genome sequencing (WGS). IGDs cause a series of overlapping phenotypes consisting of seizures, dysmorphic features, multiple congenital malformations, and severe intellectual disability. We present a study of six individuals from three unrelated families in which WES or WGS identified bi-allelic phosphatidylinositol glycan class S (PIGS) biosynthesis mutations. Phenotypes included severe global developmental delay, seizures (partly responding to pyridoxine), hypotonia, weakness, ataxia, and dysmorphic facial features. Two of them had compound-heterozygous variants c.108G>A (p.Trp36 Show less

Inhibition of cholesteryl ester transfer protein by evacetrapib when added to atorvastatin may provide an additional treatment option for patients who do not reach their low-density lipoprotein cholesterol (LDL-C) goal. This multicenter, randomized, 12-week, double-blind, parallel-group, placebo-controlled, outpatient, phase 3 study evaluated the efficacy of evacetrapib with atorvastatin in reducing LDL-C in 149 Japanese patients (evacetrapib/atorvastatin, n=53; ezetimibe/atorvastatin, n=50; placebo/atorvastatin, n=46) with primary hypercholesterolemia. The primary efficacy measure was percent change from baseline to week 12 in LDL-C (β quantification). Treatment with evacetrapib 130 mg daily for 12 weeks resulted in a statistically significant treatment difference of -25.70% compared with placebo in percentage decrease in LDL-C (95% CI: -34.73 to -16.68; P<0.001). Treatment with evacetrapib 130 mg also resulted in a statistically significant difference of 126.39% in the change in high-density lipoprotein cholesterol (HDL-C) compared with placebo (95% CI: 113.54-139.24; P<0.001). No deaths or serious adverse events were reported. Four patients (3 in the evacetrapib group and 1 in the ezetimibe group) discontinued due to adverse events. Evacetrapib daily in combination with atorvastatin was superior to placebo in lowering LDL-C after 12 weeks, and resulted in a statistically significant increase of HDL-C compared with placebo. Also, no new safety risks were identified. Show less

Age-related macular degeneration (AMD) is the most common cause of vision loss in elderly individuals throughout the developed world. Inhibitors of vascular endothelial growth factor have been successfully used to treat choroidal neovascularization in late-stage AMD. The pathogenesis of early-stage AMD, however, remains largely unknown, impairing efforts to develop effective therapies that prevent progression to late-stage AMD. To address this, we performed comparative transcriptomics of macular and extramacular retinal pigmented epithelium-choroid (RPE-choroid) tissue from early-stage AMD patients. We found that expression of fatty acid desaturase 1 ( Show less

Hand grip strength is a widely used proxy of muscular fitness, a marker of frailty, and predictor of a range of morbidities and all-cause mortality. To investigate the genetic determinants of variation in grip strength, we perform a large-scale genetic discovery analysis in a combined sample of 195,180 individuals and identify 16 loci associated with grip strength (P<5 × 10 Show less

A comprehensive genome-wide screen of radiosensitization targets in HeLa cells was performed using a shRNA-library/functional cluster analysis and DNMT3B was identified as a candidate target. DNMT3B RNAi increased the sensitivity of HeLa, A549 and HCT116 cells to both γ-irradiation and carbon-ion beam irradiation. DNMT3B RNAi reduced the activation of DNA damage responses induced by γ-irradiation, including HP1β-, γH2AX- and Rad51-foci formation. DNMT3B RNAi impaired damage-dependent H2AX accumulation and showed a reduced level of γH2AX induction after γ-irradiation. DNMT3B interacted with HP1β in non-irradiated conditions, whereas irradiation abrogated the DNMT3B/HP1β complex but induced interaction between DNMT3B and H2AX. Consistent with radiosensitization, TP63, BAX, PUMA and NOXA expression was induced after γ-irradiation in DNMT3B knockdown cells. Together with the observation that H2AX overexpression canceled radiosensitization by DNMT3B RNAi, these results suggest that DNMT3B RNAi induced radiosensitization through impairment of damage-dependent HP1β foci formation and efficient γH2AX-induction mechanisms including H2AX accumulation. Enhanced radiosensitivity by DNMT3B RNAi was also observed in a tumor xenograft model. Taken together, the current study implies that comprehensive screening accompanied by a cluster analysis enabled the identification of radiosensitization targets. Downregulation of DNMT3B, one of the targets identified using this method, radiosensitizes cancer cells by disturbing multiple DNA damage responses. Show less

We propose Langerhans cell histiocytosis (LCH) is an inflammatory process that is prolonged by mutations. We hypothesize that Merkel cell polyomavirus (MCPyV) infection triggers an interleukin-1 (IL-1) activation loop that underlies the pathogenesis of LCH. Langerhans cells (LCs) are antigen presenting cells in the skin. When LCs encounter exogenous antigens, they migrate from the epidermis into draining lymphoid tissues to initiate T-cell activity. It has been proposed that LC migration-related factors, including E-cadherin, matrix metalloproteinase, and Notch ligand induce LCH activity. We found that the tyrosine phosphatase SHP-1, which binds IL-1 receptor-associated kinase 1, is expressed at a significantly higher level in LCH affecting multiple organ systems (MS-LCH) than in LCH affecting a single organ system (SS-LCH). IL-1 stimulates T helper 17 cells and their signature cytokine IL-17 had been a matter of controversy. We detected higher levels of IL-17A receptor expression in MS-LCH than in SS-LCH and proposed an IL-17 endocrine model that could settle the controversy. IL-1 is the first cytokine secreted in response to sensitizers and promotes LC migration from sentinel tissues. Myeloid differentiation primary response 88 (MyD88), downstream of the IL-1 receptor, has functions in both RAS signaling and inflammation, leading to human cell transformation. In 2010, an activating mutation in the B-rapidly accelerated fibrosarcoma gene (BRAF) V600E was found in LCH. This BRAF mutation induces phosphorylation of the extracellular signal-regulated kinase (ERK) that may play an important role with MyD88 in LCH pathogenesis. However, phosphorylated ERK (pERK) is rapidly dephosphorylated by dual specificity phosphatase 6 (DUSP6), and limited proliferation is predicted in BRAF mutant cells. MyD88 binds pERK via its D-domain, thereby preventing pERK-DUSP6 interaction and maintaining ERK in an active, phosphorylated state. We detected MCPyV-DNA in the peripheral blood cells of two out of three patients with LCH in high-risk organs but not in those of patients with LCH in non-high-risk organs (0/12; P = .029). MCPyV infection can trigger precursor LCH cells with BRAF mutation to produce IL-1; the IL-1 loop is amplified in all LCH subclasses. Our model indicates both BRAF mutation and IL-1 loop regulation as potential therapeutic targets. Show less

The kinetochore is a supramolecular structure essential for microtubule attachment and the mitotic checkpoint. Human blinkin/human Spc105 (hSpc105)/hKNL1 was identified originally as a mixed-lineage leukemia (MLL) fusion partner and later as a kinetochore component. Blinkin directly binds to several structural and regulatory proteins, but the precise binding sites have not been defined. Here, we report distinct and essential binding domains for Bub1 and BubR1 (here designated Bubs) at the N terminus of blinkin and for Zwint-1 and hMis14/hNsl1 at the C terminus. The minimal binding sites for Bub1 and BubR1 are separate but contain a consensus KI motif, KI(D/N)XXXF(L/I)XXLK. RNA interference (RNAi)-mediated replacement with mutant blinkin reveals that the Bubs-binding domain is functionally important for chromosome alignment and segregation. We also provide evidence that hMis14 mediates hNdc80 binding to blinkin at the kinetochore. The C-terminal fragment of blinkin locates at kinetochores in a dominant-negative fashion by displacing endogenous blinkin from kinetochores. This negative dominance is relieved by mutations of the hMis14 binding PPSS motif on the C terminus of blinkin or by fusion of the N sequence that binds to Bub1 and BubR1. Taken together, these results indicate that blinkin functions to connect Bub1 and BubR1 with the hMis12, Ndc80, and Zwint-1 complexes, and disruption of this connection may lead to tumorigenesis. Show less

Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a key regulator in hepatic lipid metabolism and is a potential therapeutic target for dyslipidaemia. We reported previously that human hepatic apoA-IV is a highly sensitive gene up-regulated by the PPARalpha agonist KRP-101 (KRP), suggesting that induction of apoA-IV expression is one of the mechanisms underlying the decrease in triglycerides and elevation of HDL observed with PPARalpha agonist treatment. However, the mechanism of transcriptional regulation of apoA-IV by PPARalpha activation remains unclear. To clarify whether the apoA-IV promoter is regulated directly by PPARalpha, we analysed the apoA-IV promoter region by transient transfection assay in the human hepatocellular carcinoma cell line, HepG2. Co-transfection assay of unilateral deletions of apoA-IV promoter construct with human PPARalpha/RXRalpha showed that the region from -3279 to -2261 of the apoA-IV promoter includes key sites for transactivation by PPARalpha/RXRalpha. Sequence analysis suggested three putative PPAR response elements (PPREs) in this region. Electrophoretic mobility shift assay (EMSA) showed that a PPRE located from -2979 to -2967 can bind to PPARalpha/RXRalpha. Moreover, site-directed mutagenesis experiments indicated that the -2979/-2967 PPRE plays an essential role in transcriptional regulation of apoA-IV by PPARalpha. Chromatin immunoprecipitation (ChIP) assay confirmed that ligand-induced binding of PPARalpha to endogenous -2979/-2967 PPRE. These results indicate that human apoA-IV is regulated directly by PPARalphavia the -2979/-2967 PPRE. Show less

The tumor suppressor, CADM1, is involved in cell adhesion and preferentially inactivated in invasive cancer. We have previously reported that CADM1 associates with an actin-binding protein, 4.1B/DAL-1, and a scaffold protein, membrane protein palmitoylated 3 (MPP3)/DLG3. However, underlying mechanism of tumor suppression by CADM1 is not clarified yet. Here, we demonstrate that MPP1/p55 and MPP2/DLG2, as well as MPP3, interact with both CADM1 and 4.1B, forming a tripartite complex. We then examined cell biological roles of CADM1 and its complex in epithelia using HEK293 cells. Among MPP1-3, MPP2 is recruited to the CADM1-4.1B complex in the early process of adhesion in HEK293 cells. By suppression of CADM1 expression using siRNA, HEK293 lose epithelia-like structure and show flat morphology with immature cell adhesion. 4.1B and MPP2, as well as E-cadherin and ZO-1, are mislocalized from the membrane by depletion of CADM1 in HEK293. Mislocalization of MPP2 is also observed in several cancer cells lacking CADM1 expression with the transformed morphology. These findings suggest that CADM1 is involved in the formation of epithelia-like cell structure with 4.1B and MPP2, while loss of its function could cause morphological transformation of cancer cells. Show less

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a key regulator in hepatic lipid metabolism and a potential therapeutic target for dyslipidemia. However, in humans hepatic PPARalpha-regulated genes remain unclear. To investigate the effect of PPARalpha agonism on mRNA expressions of lipid metabolism-related genes in human livers, a potent PPARalpha agonist, KRP-101 (KRP), was used to treat the human hepatoma cell line, HepaRG cells. KRP did not affect AOX or L-PBE, which are involved in peroxisomal beta-oxidation. KRP increased L-FABP, CPT1A, VLCAD, and PDK4, which are involved in lipid transport or oxidation. However, the EC(50) values (114-2500 nM) were >10-fold weaker than the EC(50) value (10.9 nM) for human PPARalpha in a transactivation assay. To search for more sensitive genes, we determined the mRNA levels of apolipoproteins, apoA-I, apoA-II, apoA-IV, apoA-V, and apoC-III. KRP had no or little effect on apoA-I, apoC-III, and apoA-II. Interestingly, KRP increased apoA-IV (EC(50), 0.99 nM) and apoA-V (EC(50), 0.29 nM) with high sensitivity. We identified apoA-IV as a PPARalpha-upregulated gene in a study using PPARalpha siRNA. Moreover, when administered orally to dogs, KRP decreased the serum triglyceride level and increased the serum apoA-IV level in a dose-dependent manner. These findings suggest that apoA-IV, newly identified as a highly sensitive PPARalpha-regulated gene in human livers, may be one of the mechanisms underlying PPARalpha agonist-induced triglyceride decrease and HDL elevation. Show less

Combinatorial actions of transcription factors in multiprotein complexes dictate gene expression profiles in cardiac development and disease. The Hairy-related transcription factor (HRT) family of basic helix-loop-helix proteins is composed of transcriptional repressors highly expressed in the cardiovascular system. However, it has remained unclear whether HRT proteins modulate gene expression driven by cardiac transcriptional activators. Here, we have shown that HRT proteins inhibit cardiac gene transcription by interfering with GATA transcription factors that are implicated in cardiac development and hypertrophy. HRT proteins inhibited GATA-dependent transcriptional activation of cardiac gene promoters such as the atrial natriuretic factor (ANF) promoter. Adenovirus-mediated expression of Hrt2 suppressed mRNA expression of ANF and other cardiac-specific genes in cultured cardiomyocytes. Among various signaling molecules implicated in cardiomyocyte growth, constitutively active Akt1/protein kinase B alpha relieved Hrt2-mediated inhibition of GATA-dependent transcription. HRT proteins physically interacted with GATA proteins, and the basic domain of HRT was critical for physical association as well as transcriptional inhibition. These results suggest that HRT proteins may regulate specific sets of cardiac genes by modulating the function of GATA proteins and other cardiac transcriptional activators in a signal-dependent manner. Show less