Rheumatoid arthritis (RA) is one of the most critical articular diseases with synovial hyperplasia followed by impairment of quality of life. However, the mechanism(s) that regulates synovial cell outgrowth is not fully understood. To clarify its mechanism(s), we carried out immunoscreening by using antirheumatoid synovial cell antibody and identified and cloned "Synoviolin/Hrd1", an E3 ubiquitin ligase. Synoviolin/Hrd1 was highly expressed in the rheumatoid synovium, and mice overexpressing this enzyme developed spontaneous arthropathy. Conversely, synoviolin/hrd1 +/− mice were resistant to collagen-induced arthritis by enhanced apoptosis of synovial cells. We conclude that Synoviolin/Hrd1 is a novel causative factor for arthropathy by triggering synovial cell outgrowth through its antiapoptotic effects. Our findings provide a new pathogenetic model of RA and suggest that Synoviolin/Hrd1 could be targeted as a therapeutic strategy for RA.

Synoviolin, also called HRD1, is an E3 ubiquitin ligase and is implicated in endoplasmic reticulum -associated degradation. In mammals, Synoviolin plays crucial roles in various physiological and pathological processes, including embryogenesis and the pathogenesis of arthropathy. However, little is known about the molecular mechanisms of Synoviolin in these actions. To clarify these issues, we analyzed the profile of protein expression in synoviolinnull cells. Here, we report that Synoviolin targets tumor suppressor gene p53 for ubiquitination. Synoviolin sequestrated and metabolized p53 in the cytoplasm and negatively regulated its cellular level and biological functions, including transcription, cell cycle regulation and apoptosis. Furthermore, these p53 regulatory functions of Synoviolin were irrelevant to other E3 ubiquitin ligases for p53, such as MDM2, Pirh2 and Cop1, which form autoregulatory feedback loops. Our results provide novel insights into p53 signaling mediated by Synoviolin.

BackgroundHuman T-lymphotropic virus type 1 (HTLV-1) is a human retrovirus associated with both HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), which is a chronic neuroinflammatory disease, and adult T-cell leukemia (ATL). The pathogenesis of HAM/TSP is known to be as follows: HTLV-1-infected T cells trigger a hyperimmune response leading to neuroinflammation. However, the HTLV-1-infected T cell subset that plays a major role in the accelerated immune response has not yet been identified.Principal FindingsHere, we demonstrate that CD4+CD25+CCR4+ T cells are the predominant viral reservoir, and their levels are increased in HAM/TSP patients. While CCR4 is known to be selectively expressed on T helper type 2 (Th2), Th17, and regulatory T (Treg) cells in healthy individuals, we demonstrate that IFN-γ production is extraordinarily increased and IL-4, IL-10, IL-17, and Foxp3 expression is decreased in the CD4+CD25+CCR4+ T cells of HAM/TSP patients as compared to those in healthy individuals, and the alteration in function is specific to this cell subtype. Notably, the frequency of IFN-γ-producing CD4+CD25+CCR4+Foxp3− T cells is dramatically increased in HAM/TSP patients, and this was found to be correlated with disease activity and severity.ConclusionsWe have defined a unique T cell subset—IFN-γ+CCR4+CD4+CD25+ T cells—that is abnormally increased and functionally altered in this retrovirus-associated inflammatory disorder of the central nervous system.

RNA helicase A (RHA) is a member of an ATPase/DNA and RNA helicase family and is a homologue of Drosophila maleless protein (MLE), which regulates X-linked gene expression. RHA is also a component of holo-RNA polymerase II (Pol II) complexes and recruits Pol II to the CREB binding protein (CBP). The ATPase and/or helicase activity of RHA is required for CREB-dependent transcription. To further understand the role of RHA on gene expression, we have identified a 50-amino-acid transactivation domain that interacts with Pol II and termed it the minimal transactivation domain (MTAD). The protein sequence of this region contains six hydrophobic residues and is unique to RHA homologues and well conserved. A mutant with this region deleted from full-length RHA decreased transcriptional activity in CREB-dependent transcription. In addition, mutational analyses revealed that several tryptophan residues in MTAD are important for the interaction with Pol II and transactivation. These mutants had ATP binding and ATPase activities comparable to those of wild-type RHA. A mutant lacking ATP binding activity was still able to interact with Pol II. In CREB-dependent transcription, the transcriptional activity of each of these mutants was less than that of wild-type RHA. The activity of the double mutant lacking both functions was significantly lower than that of each mutant alone, and the double mutant had a dominant negative effect. These results suggest that RHA could independently regulate CREB-dependent transcription either through recruitment of Pol II or by ATP-dependent mechanisms.RNA helicase A (RHA) is a member of the DExH family of ATPases/helicases and catalyzes the displacement of both double-stranded RNA and DNA from 3Ј to 5Ј (32,61,63). Functional domains of RHA include two double-stranded RNA binding domains at the amino terminus known as dsRBD1 and dsRBD2. The catalytic core domain is located within the central region and contains a DExH motif. This core domain contains seven well-conserved motifs; one of them has an ATP binding site with the consensus GCGKT and FILDD, known as the A site the B site, respectively. The carboxyl terminus contains an RGG-rich region that is capable of binding singlestrand nucleic acids (62).RHA was originally isolated as a human homologue of Drosophila maleless protein (MLE), with which it has 50% sequence identity and 90% sequence similarity (33). In Drosophila, MLE colocalizes with acetylated histone H4 (8, 48). MLE is involved in sex-specific gene dosage compensation and elevates the level of transcription derived from a single X chromosome in male flies to a level equivalent to that derived from two X chromosome in the female (25,29). MLE mutants are embryonic lethal to males, indicating that MLE is an essential factor in Drosophila development.In mammals, RHA-knockout mice are embryonic lethal for homozygous RHA mutants (35). Analysis of these mice revealed that RHA is associated with differentiation of the embryonic ectoderm during gastrulation. It is possible that RHA has an i...

Obesity is a major global public health problem, and understanding its pathogenesis is critical for identifying a cure. In this study, a gene knockout strategy was used in post-neonatal mice to delete synoviolin (Syvn)1/Hrd1/Der3, an ER-resident E3 ubiquitin ligase with known roles in homeostasis maintenance. Syvn1 deficiency resulted in weight loss and lower accumulation of white adipose tissue in otherwise wild-type animals as well as in genetically obese (ob/ob and db/db) and adipose tissue-specific knockout mice as compared to control animals. SYVN1 interacted with and ubiquitinated the thermogenic coactivator peroxisome proliferatoractivated receptor coactivator (PGC)-1b, and Syvn1 mutants showed upregulation of PGC-1b target genes and increase in mitochondrion number, respiration, and basal energy expenditure in adipose tissue relative to control animals. Moreover, the selective SYVN1 inhibitor LS-102 abolished the negative regulation of PGC-1b by SYVN1 and prevented weight gain in mice. Thus, SYVN1 is a novel post-translational regulator of PGC-1b and a potential therapeutic target in obesity treatment.

Although it has been reported that hypoxia inducible factor 2 α (Hif2a), a major transcriptional factor inducible by low oxygen tension, is expressed in the mouse uterus during embryo implantation, its role in pregnancy outcomes remains unclear. This study aimed to clarify functions of uterine HIF using transgenic mouse models. Mice with deletion of Hif2a in the whole uterus (Hif2a-uKO mice) showed infertility due to implantation failure. Supplementation with progesterone (P4) and leukemia inhibitory factor (LIF) restored decidual growth arrest and aberrant position of implantation sites in Hif2a-uKO mice, respectively, but did not rescue pregnancy failure. Histological analyses in Hif2a-uKO mice revealed persistence of the intact luminal epithelium, which blocked direct contact between stroma and embryo, inactivation of PI3K-AKT pathway (embryonic survival signal), and failed embryo invasion. Mice with stromal deletion of Hif2a (Hif2a-sKO mice) showed infertility with impaired embryo invasion and those with epithelial deletion of Hif2a (Hif2a-eKO mice) showed normal fertility, suggesting the importance of stromal HIF2α in embryo invasion. This was reflected in reduced expression of membrane type 2 metalloproteinase (MT2-MMP), lysyl oxidase (LOX), VEGF, and adrenomedullin (ADM) in Hif2a-uKO stroma at the attachment site, suggesting that stromal HIF2α regulates these mediators to support blastocyst invasion. These findings provide new insight that stromal HIF2α allows trophoblast invasion through detachment of the luminal epithelium and activation of an embryonic survival signal.

Invariant natural killer T (iNKT) cells are unique T cells that regulate the immune response to microbes, cancers, and autoimmunity. We assessed the characteristics of iNKT cells from persons infected with human T-lymphotropic virus type 1 (HTLV-1). Whereas most infected persons remain asymptomatic carriers (ACs IntroductionHuman T-cell lymphotropic virus type 1 (HTLV-1) causes persistent infection. Whereas most infected persons remain asymptomatic carriers (ACs), 3% to 5% develop a T-cell malignancy termed adult T-cell leukemia (ATL), and another 0.25% to 3% develop a chronic progressive inflammatory neurologic disease known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/ TSP). [1][2][3] One of the most important pathogenic factors in HAM/ TSP is an increased HTLV-1 load in the peripheral blood mononuclear cells (PBMCs) and cerebrospinal fluid, 4-6 which suggests that in affected persons, virus control is inadequate. A higher HTLV-1 load increases the risk of HAM/TSP and ATL. 4,7 Therefore, the precise mechanisms controlling HTLV-1-infected cells must be better understood. With regard to the host defense mechanisms involved in HTLV-1 infection, the role of HTLV-1-specific CD8 ϩ cytotoxic T lymphocytes (CTLs) has been studied. [8][9][10] The HTLV-1-specific CTL response is critical for a low viral load to be maintained. [9][10][11] Despite the high frequency of HTLV-1-specific CTLs, the number of HTLV-1-infected T cells is surprisingly high in HAM/TSP patients. 5,6 We and others have reported that the maturation and functioning of HTLV-1-specific CTLs are inadequate in HAM/TSP patients, although in vitro studies have shown that these CTLs exert cytolytic activity against HTLV-1-expressing target cells. 12,13 Therefore, we hypothesize that there may be another cell population without CTLs that contributes to the control of HTLV-1-infected T cells.A unique T-cell subpopulation, natural killer T (NKT) cells, constitute a subset of lymphocytes that share the features of both innate and adaptive immune cells. Unlike conventional T cells, NKT cells express a T-cell receptor (TCR) that recognizes glycolipids instead of protein antigens. Moreover, these cells share properties and receptors with NK cells. They rapidly produce granzymes and perforins on stimulation. Among the CD3 ϩ T cells in human blood, 10% to 25% express NK cell-surface molecules, such as CD161, and these can be classified as NKT cells. 14,15 A small population of T cells within this NKT cell subset expresses a highly conserved V␣24J␣18 TCR chain that associates preferentially with V␤11. [16][17][18] These T cells are referred to as invariant NKT (iNKT) cells. Very recently, a novel clonotypic monoclonal antibody 6B11 specific for the V␣24J␣18 TCR chain has been shown to selectively stain human iNKT cells. 18,19 Activation of human iNKT cells requires the presentation of glycolipids, such as ␣-galactosylceramide (␣-GalCer) on the major histocompatibility complex class I-like molecule CD1d. 20 ␣-GalCer stimulation induces rapid cytoki...

ABSTRACT:In term neonates, the adiponectin concentration is higher than it is in adults. To determine the relationship between adiponectin and early neonatal growth in a cohort study. Fifty-two neonates at term were studied. Serum adiponectin concentrations, body sizes, and skinfold thicknesses were measured at birth and at 1 mo of age. At birth, cord blood adiponectin concentration correlated positively with birth weight (r ϭ 0.484, p ϭ 0.0003), birth length (r ϭ 0.524, p Ͻ 0.0001), and sum of the four skinfold thickness measurements (r ϭ 0.378, p ϭ 0.0057). In a stepwise regression, birth length was the only determinant of cord blood adiponectin concentration. However, at 1 mo of age, serum adiponectin concentration correlated with no anthropometric parameter at all. Between birth and 1 mo of age, the individual change in adiponectin concentration correlated negatively with birth weight. Thus, serum adiponectin concentrations in cord blood have a strong relationship to birth length rather than to body fatness, and this relationship is not demonstrated in 1-mo-old infants. These results imply that hormonal, substrate, or other mechanisms that regulate the relationship between body composition and growth in fetal life are different from those governing these relationships in early postnatal life. A diponectin is an adipocytokine produced exclusively by adipocytes and has potential antidiabetic, antiatherosclerotic, and anti-inflammatory properties. Therefore, serum adiponectin concentration may be applied usefully as a biomarker of metabolic syndrome (1). Paradoxically, however, adiponectin concentration is inversely correlated with body fatness in adults (2) and in children (3), unlike the other adipocytokines, such as leptin, interleukin (IL)-6, and tumor necrosis factor (TNF) ␣. Overall, the regulation of adiponectin concentrations and its functions are still not sufficiently understood, especially in growing infants.Adiponectin is also abundantly present in cord blood of term neonates, at concentrations two to three times higher than those reported in adults (2,4). Recent studies suggest that low adiponectin concentration in small neonates may be one of the mechanisms underlying the long-term consequences of an adverse fetal environment (5) and that small size at birth is associated with increased rates of the metabolic syndrome (6). However, adiponectin must have physiologic functions in the fetus and in neonates other than that of merely serving as a biomarker for the development of the metabolic syndrome. Little is known about the roles of adiponectin in the fetus. Recent studies in cord blood suggest that adiponectin, which is positively associated with birth weight, may play an important role in regulating fetal growth (7,8). Furthermore, adiponectin concentration in cord blood correlates positively with gestational age, increasing as the amount of adipose tissue also increases during the last trimester (8). This is in marked contrast to findings in adulthood where increased adiposity is associated with...