Developmentally-regulated expression of tissue-specific splice variant of rat vesicular glutamate transporter 1 in retina and pineal gland

Three distinct subtypes of vesicular glutamate transporters (VGLUTs) have been identified to date that are expressed basically in a cell type-specific manner. We have found a splice variant of VGLUT1 mRNA that is expressed almost exclusively in photosensitive tissues, i.e. the retina and the pineal gland. The variant mRNA, termed VGLUT1v, contains an additional 75 base pair sequence derived from part of a second intron (designated as exon IIa) between exons 2 and 3. The variant accounted for approximately 70% and 25%of VGLUT1 mRNA in the adult retina and pineal gland, respectively. The expression of VGLUT1v was developmentally regulated in both tissues. Organ culture showed that expression of the variant in the retina increased in association with the development of rod cells, suggesting that VGLUT1v is expressed in rod cells. In situ hybridization with variant-specific probes showed expression of VGLUT1v in the inner segment layer of photoreceptor cells. On the other hand, variant expression did not parallel the development of rhodopsin-positive cells in the pineal gland. As rod cells and pinealocytes are known to release glutamate continuously at ribbon synapses, it is possible that the variant has some functional advantage over the wild-type transporter in such a specialized manner of glutamate release.     

Rapid induction of REDD1 expression by endurance exercise in rat skeletal muscle

An acute bout of exercise induces repression of protein synthesis in skeletal muscle due in part to reduced signaling through the mammalian target of rapamycin complex 1 (mTORC1). Previous studies have shown that upregulated expression of regulated in DNA damage and development (REDD) 1 and 2 is an important mechanism in the regulation of mTORC1 activity in response to a variety of stresses. This study investigated whether induction of REDD1/2 expression occurs in rat skeletal muscle in response to a burst of endurance exercise. In addition, we determined if ingestion of glucose or branched chain amino acids (BCAA) before exercise changes the expression of REDD1/2 in muscle. Rats ran on a motor-driven treadmill at a speed of 28 m min⁻¹ for 90 min, and then the gastrocnemius muscle was removed and analyzed for phosphorylation of the eukaryotic initiation factor (eIF) 4E binding protein 1 (4E-BP1) and expression of REDD1/2. Exercise repressed the mTORC1-signaling pathway regardless of the ingestion of nutrients before the exercise, as shown by dephosphorylation of 4E-BP1. In addition, exercise induced the expression of REDD1 mRNA (∼8-fold) and protein (∼3-fold). Exercise-induced expression of REDD1 was not affected by the ingestion of glucose or BCAA. Expression of REDD2 mRNA was not altered by either exercise or nutrients. These findings indicated that enhanced expression of REDD1 may be an important mechanism that could partially explain the downregulation of mTORC1 signaling, and subsequent inhibition of protein synthesis in skeletal muscle during exercise.     

Thymus, innate immunity and autoimmune arthritis: interplay of gene and environment

A hypomorphic mutation of the gene encoding zeta-associated protein-70 (ZAP-70), a signaling molecule in T cells, produces autoimmune arthritis in mice under a microbially conventional condition but not in a clean environment. The genetic anomaly alters thymic selection of self-reactive T cells as well as natural regulatory T cells and their respective functions. Highly self-reactive polyclonal T cells, including arthritogenic ones, thus produced by the thymus strongly recognize self-antigens presented by antigen-presenting cells, stimulate them to up-regulate co-stimulatory molecules and secrete cytokines that drive na?ve self-reactive T cells to differentiate into autoimmune effector Th17 cells. Administration of microbial products and activation of complement can facilitate the differentiation, evoking clinically overt arthritis in a microbially clean environment. Furthermore, mutation-dependent graded attenuation of T cell receptor signaling alters disease phenotypes and the dependency of disease occurrence on the environment. These findings provide a model of how genetic and environmental factors, in association, cause autoimmune diseases such as rheumatoid arthritis.     

Coronaviruses

Coronaviruses contain positive-stranded RNA with ca. 30 kb as a genome, which is wrapped by the envelope, and constitute Nidovirales together with Arteriviridae. The feature of viruses in Nidovirales is the unique structure of the mRNA set, called 3' co-terminal nested set. Coronaviruses have several to more than 10 different species of subgenomic mRNA and generally only the OFR located in the 5' end of each mRNA is translated. The 5' 20 kb of the coronavirus genome or mRNA-1 consists of two ORFs, 1a and 1b, between that there is a unique RNA structure called pseudoknot. From mRNA-1, 1a as well as 1a+1b are translated; the latter 1a+1b results from the translation due to ribosomal frame-shifting facilitated by the pseudoknot structure. From those two proteins, totally 16 proteins are produced as a result of auto-cleavage by the proteases included in la protein. Those proteins exhibit different functions, such as RNA-dependent RNA polymerase, helicase, proteases and proteins that regulate cellular functions, mRNAs smaller than mRNA-2 translate in general the structural proteins, nucleocapsid (N) protein, spike (S) protein, integrated membrane (M) protein and envelope (E) proteins. Those proteins assemble to the vesicles located from ER to Golgi (ER Golgi intermediate compartment) and virions bud into the vesicles. Those virions are released from infected cells via exocytosis.     

In vitro biosynthesis of volicitin in Spodoptera litura

Volicitin [N-(17-hydroxylinolenoyl)-L-glutamine] and N-linolenoyl-L-glutamine, originally identified in the regurgitant of Spodoptera exigua, induce damaged corn leaves to release volatile compounds which enable parasitic wasps to locate host caterpillars. Here we demonstrate the in vitro biosynthesis of volicitin for the first time by using gut tissues of Spodoptera litura larvae, as well as N-linolenoyl-L-glutamine. When crop, midgut tissues, peritrophic membrane and gut contents isolated from S. litura were incubated with sodium linolenate and L-[alpha-15N] glutamine, not only 15N-labeled N-linolenoyl-L-glutamine but 15N-labeled volicitin was detected mainly in the midgut incubation by LCMS and LCMSMS analysis. In contrast, there were negligible amounts of the newly biosynthesized compounds in the gut content incubation. Furthermore, the microsomal fraction obtained from the gut tissues clearly showed specific incorporation of glutamine. This substrate selectivity accounts for the exclusive uptake of glutamine by fatty acid amides (FAAs) in the noctuid caterpillars, even though glutamine was not a major component in the regurgitant. Additionally, intensive chemical analyses revealed that more than 20% of glutamine in hemolymph was present as conjugates in gut contents. These results suggest that FAA compounds are actively synthesized by caterpillar tissues and might play important physiological role(s) in glutamine metabolism.     

Adoptive transfer of genetically engineered WT1-specific cytotoxic T lymphocytes does not induce renal injury

Because WT1 is expressed in leukemia cells, the development of cancer immunotherapy targeting WT1 has been an attractive translational research topic. However, concern of this therapy still remains, since WT1 is abundantly expressed in renal glomerular podocytes. In the present study, we clearly showed that WT1-specific cytotoxic T lymphocytes (CTLs) certainly exerted cytotoxicity against podocytes in vitro; however, they did not damage podocytes in vivo. This might be due to the anatomical localization of podocytes, being structurally separated from circulating CTLs in glomerular capillaries by an exceptionally thick basement membrane.     

Induction of Plant Tubers and Flower Buds under Noninducing Photoperiod Conditions by a Natural Product, Theobroxide

   apd: 9 May 2001     

Isolation and characterization of a novel mycovirus infecting an edible mushroom,Grifola frondosa

Grifola frondosa (Maitake mushroom) is an important cultivated mushroom due to its medicinal and nutrient values. In this study, we isolated and characterized a novel partitivirus (named Grifola frondosa partitivirus 1, GfPV1) infecting a standard G. frondosa strain Gf-N2. This virus has a two-segmented dsRNA genome (dsRNA1 and dsRNA2) with nucleotide lengths of 2.3 and 2.2 kbp, respectively. The coding strand of dsRNA1 and dsRNA2 segments carries single open reading frame encoding RNA-dependent RNA polymerase (RdRp) and a coat protein (CP), respectively. BLAST searches and phylogenetic analyses showed that GfPV1 is most closely related to a betapartitivirus, Lentinula edodes partitivirus 1 (RdRp <70% and CP <60% amino acid sequence identities), but the sequence divergence suggests that GfPV1 is classifiable as a new member of the genus Betapartitivirus, family Partitiviridae. The presence of GfPV1 does not affect colony morphology and fruiting body development of G. frondosa. This is the first report investigating the effects of a mycovirus infection on the colony morphology and fruiting body development of G. frondosa. Interestingly, GfPV1 accumulations markedly decreased along with the fruiting body maturation stages, suggesting the inhibition of virus multiplication during sexual phase of the G. frondosa life cycle.     

Porcine brain natriuretic peptide-like immunoreactivity in rat tissues

The presence of immunoreactive porcine brain natriuretic peptide in rat tissues was studied with a specific radioimmunoassay for porcine brain natriuretic peptide-26. The cross-reactivity of the antiserum used was less than 0.001% with rat atrial natriuretic peptide, rat brain natriuretic peptide-32 and rat brain natriuretic peptide-45. Immunoreactive porcine brain natriuretic peptide was detectable in various tissues of the rat, and high concentrations of immunoreactive porcine brain natriuretic peptide were found in the brain and cardiac atrium, with the highest level in the hypothalamus (159±30 fmol/gram wet tissue, mean±SEM, n=4). Reverse phase high performance liquid chromatography showed that the immunoreactive porcine brain natriuretic peptide of the whole brain and heart extracts eluted mainly at an identical position to synthetic porcine brain natriuretic peptide-26. These findings indicate that porcine brain natriuretic peptide-like substance, distinct from rat brain natriuretic peptide, is present in high concentrations in the rat brain and cardiac atrium.