SRPX2 is a novel chondroitin sulfate proteoglycan that is overexpressed in gastrointestinal cancer

SRPX2 (Sushi repeat-containing protein, X-linked 2) has recently emerged as a multifunctional protein that is involved in seizure disorders, angiogenesis and cellular adhesion. Here, we analyzed this protein biochemically. SRPX2 protein was secreted with a highly posttranslational modification. Chondroitinase ABC treatment completely decreased the molecular mass of purified SRPX2 protein to its predicted size, whereas heparitinase, keratanase and hyaluroinidase did not. Secreted SRPX2 protein was also detected using an anti-chondroitin sulfate antibody. These results indicate that SRPX2 is a novel chondroitin sulfate proteoglycan (CSPG). Furthermore, a binding assay revealed that hepatocyte growth factor dose-dependently binds to SRPX2 protein, and a ligand-glycosaminoglycans interaction was speculated to be likely in proteoglycans. Regarding its molecular architecture, SRPX2 has sushi repeat modules similar to four other CSPGs/lecticans; however, the molecular architecture of SRPX2 seems to be quite different from that of the lecticans. Taken together, we found that SRPX2 is a novel CSPG that is overexpressed in gastrointestinal cancer cells. Our findings provide key glycobiological insight into SRPX2 in cancer cells and demonstrate that SRPX2 is a new member of the cancer-related proteoglycan family.     

Circadian rhythm of circumnutation in inflorescence stems of Arabidopsis

We investigate the modulation of circumnutation in inflorescence stems of Arabidopsis to determine the circadian regulation of circumnutation. Under constant light conditions (LL), circumnutation speed in wild-type plants fluctuates, with the phase of the highest speed at subjective dawn; the period length is close to 24 h. toc1 appears to shorten the period and elf3 causes an arrhythmic phenotype in circumnutation speed in LL, suggesting that a common circadian clock may control both circumnutation speed and other circadian outputs. These results highlight for the first time a role for a circadian clock in the regulation of circumnutation based on genetic analysis of Arabidopsis.     

Cellular and subcellular localization of kainic acid in the marine red alga Digenea simplex

Polyclonal antibodies specific for the excitatory amino acid, kainic acid (KA), were raised in rabbits. The antibody recognized KA but did not cross-react with other structurally related amino acids, including glutamate. We used this anti-KA antibody to localize KA immunohistochemically in the KA-producing red alga Digenea simplex. KA immunoreactivity was most dense in the fine cylindrical thallus, which covers the middle to upper part of the alga. The cortical cells, but not the inner layers of the main axis, and cells of the rhizoid were also stained with this antibody. The presence of KA in cells that cover the surface of the alga might reflect its role in chemical defense. At the subcellular level, KA immunoreactivity was most intense in the nucleus, pit plugs, and the electron-dense areas denoted as “granule bodies”, which were found only in the pericentral cells of the thallus. This research was supported by Ministry of Education, Culture, Sports, Science and Technology to R.S. (13660206).     

Mitochondrial Mislocalization Underlies Aβ42-Induced Neuronal Dysfunction in a Drosophila Model of Alzheimer's Disease

The amyloid-β 42 (Aβ42) is thought to play a central role in the pathogenesis of Alzheimer''s disease (AD). However, the molecular mechanisms by which Aβ42 induces neuronal dysfunction and degeneration remain elusive. Mitochondrial dysfunctions are implicated in AD brains. Whether mitochondrial dysfunctions are merely a consequence of AD pathology, or are early seminal events in AD pathogenesis remains to be determined. Here, we show that Aβ42 induces mitochondrial mislocalization, which contributes to Aβ42-induced neuronal dysfunction in a transgenic Drosophila model. In the Aβ42 fly brain, mitochondria were reduced in axons and dendrites, and accumulated in the somata without severe mitochondrial damage or neurodegeneration. In contrast, organization of microtubule or global axonal transport was not significantly altered at this stage. Aβ42-induced behavioral defects were exacerbated by genetic reductions in mitochondrial transport, and were modulated by cAMP levels and PKA activity. Levels of putative PKA substrate phosphoproteins were reduced in the Aβ42 fly brains. Importantly, perturbations in mitochondrial transport in neurons were sufficient to disrupt PKA signaling and induce late-onset behavioral deficits, suggesting a mechanism whereby mitochondrial mislocalization contributes to Aβ42-induced neuronal dysfunction. These results demonstrate that mislocalization of mitochondria underlies the pathogenic effects of Aβ42 in vivo.     

Isolation and characterization of a single-stranded DNA virus infecting Chaetoceros lorenzianus Grunow

Diatoms are one of the most significant primary producers in the ocean, and the importance of viruses as a potential source of mortality for diatoms has recently been recognized. Thus far, eight different diatom viruses infecting the genera Rhizosolenia and Chaetoceros have been isolated and characterized to different extents. We report the isolation of a novel diatom virus (ClorDNAV), which causes the lysis of the bloom-forming species Chaetoceros lorenzianus, and show its physiological, morphological, and genomic characteristics. The free virion was estimated to be ～34 nm in diameter. The arrangement of virus particles appearing in cross-section was basically a random aggregation in the nucleus. Occasionally, distinctive formations such as a ring-like array composed of 9 or 10 spherical virions or a centipede-like array composed of rod-shaped particles were also observed. The latent period and the burst size were estimated to be <48 h and 2.2 × 10(4) infectious units per host cell, respectively. ClorDNAV harbors a covalently closed circular single-stranded DNA (ssDNA) genome (5,813 nucleotides [nt]) that includes a partially double-stranded DNA region (979 nt). At least three major open reading frames were identified; one showed a high similarity to putative replicase-related proteins of the other ssDNA diatom viruses, Chaetoceros salsugineum DNA virus (previously reported as CsNIV) and Chaetoceros tenuissimus DNA virus. ClorDNAV is the third member of the closed circular ssDNA diatom virus group, the genus Bacilladnavirus.     

Hepatitis C virus hijacks P-body and stress granule components around lipid droplets

The microRNA miR-122 and DDX6/Rck/p54, a microRNA effector, have been implicated in hepatitis C virus (HCV) replication. In this study, we demonstrated for the first time that HCV-JFH1 infection disrupted processing (P)-body formation of the microRNA effectors DDX6, Lsm1, Xrn1, PATL1, and Ago2, but not the decapping enzyme DCP2, and dynamically redistributed these microRNA effectors to the HCV production factory around lipid droplets in HuH-7-derived RSc cells. Notably, HCV-JFH1 infection also redistributed the stress granule components GTPase-activating protein (SH3 domain)-binding protein 1 (G3BP1), ataxin-2 (ATX2), and poly(A)-binding protein 1 (PABP1) to the HCV production factory. In this regard, we found that the P-body formation of DDX6 began to be disrupted at 36 h postinfection. Consistently, G3BP1 transiently formed stress granules at 36 h postinfection. We then observed the ringlike formation of DDX6 or G3BP1 and colocalization with HCV core after 48 h postinfection, suggesting that the disruption of P-body formation and the hijacking of P-body and stress granule components occur at a late step of HCV infection. Furthermore, HCV infection could suppress stress granule formation in response to heat shock or treatment with arsenite. Importantly, we demonstrate that the accumulation of HCV RNA was significantly suppressed in DDX6, Lsm1, ATX2, and PABP1 knockdown cells after the inoculation of HCV-JFH1, suggesting that the P-body and the stress granule components are required for the HCV life cycle. Altogether, HCV seems to hijack the P-body and the stress granule components for HCV replication.     

Identification of Fungal Pathogens by Visible Microarray System in Combination with Isothermal Gene Amplification

The increasing incidence of infectious diseases caused by fungi in immunocompromised patients has encouraged researchers to develop rapid and accurate diagnosis methods. Identification of the causative fungal species is critical in deciding the appropriate treatment, but it is not easy to get satisfactory results due to the difficulty of fungal cultivation and morphological identification from clinical samples. In this study, we established a microarray system that can identify 42 species from 24 genera of clinically important fungal pathogens by using a chemical color reaction in the detection process. The array uses the internal transcribed spacer region of the rRNA gene for identification of fungal DNA at the species level. The specificity of this array was tested against a total of 355 target and nontarget fungal species. The fungal detection was succeeded directly from 10³ CFU/ml for whole blood samples, and 50 fg DNA per 1 ml of serum samples indicating that the array system we established is sensitive to identify infecting fungi from clinical sample. Furthermore, we conducted isothermal amplification in place of PCR amplification and labeling. The successful identification with PCR-amplified as well as isothermally amplified target genes demonstrated that our microarray system is an efficient and robust method for identifying a variety of fungal species in a sample.