IgA regulates the composition and function of gut microbiota. Nakajima et al. show that a heavily glycosylated monoclonal IgA coats B. theta and induces Mucus-Associated Functional Factor in vivo to enhance symbiotic interactions with commensal bacteria to maintain gut homeostasis.

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The phosphorescence emission of ruthenium complexes was applied to the optical imaging of physiological hypoxia. We prepared three complexes with hydrophobic substituents on the phenanthroline ligand and characterized their emission, which was quenched by molecular oxygen. Among the complexes synthesized in this study, a pyrene chromophore-linked ruthenium complex, Ru-Py, exhibited optimal properties for the imaging of hypoxia; the prolonged lifetime of the triplet excited state of the ruthenium chromophore, which was induced by efficient energy distribution and transfer from the pyrene unit, provided the highest sensitivity towards molecular oxygen. The introduction of hydrophobic pyrene increased the lipophilicity of the complex, leading to enhanced cellular uptake. Consequently, the bright phosphorescence of Ru-Py was seen in the cytoplasm of viable hypoxic cells, whereas the signal from aerobic cells was markedly weaker. Thus, we could clearly discriminate between hypoxic and aerobic cells by monitoring the phosphorescence emission. Furthermore, Ru-Py was applied to optical imaging in live mice. An intramuscular injection of Ru-Py successfully visualized ischemia-based hypoxia, which was constructed by leg banding.

Background-Cardiac myosin-induced myocarditis is an experimental autoimmune myocarditis (EAM) model used to investigate autoimmunological mechanisms in inflammatory heart diseases and resembles fulminant myocarditis in humans. We investigated the therapeutic role of thioredoxin-1 (TRX-1), a redox-regulatory protein with antioxidant and antiinflammatory effects, in murine EAM. Methods and Results-EAM was generated in 5-week-old male BALB/c mice by immunization with porcine cardiac myosin at days 0 and 7. Recombinant human TRX-1 (rhTRX-1), C32S/C35S mutant rhTRX-1, or saline was administered intraperitoneally every second day from day 0 to 20. In addition, rabbit anti-mouse TRX-1 serum or normal rabbit serum was administered intraperitoneally on days Ϫ1, 2, and 6. Animals were euthanized on day 21. Histological analysis of the heart showed that TRX-1 significantly reduced the severity of EAM, whereas mutant TRX-1 failed to have such an effect, and anti-TRX-1 antibody enhanced the disease markedly. Immunohistochemical analysis showed that TRX-1 significantly suppressed cardiac macrophage inflammatory protein (MIP)-1␣, MIP-2, and 8-hydroxydeoxyguanosine expression and macrophage infiltration into the heart in EAM. Although serum levels of MIP-1␣ were not suppressed by TRX-1 until day 21, both an in vitro chemotaxis chamber assay and an in vivo air pouch model showed that TRX-1 significantly suppressed MIP-1␣-or MIP-2-induced leukocyte chemotaxis. However, real-time reverse transcription-polymerase chain reaction showed that TRX-1 failed to decrease chemokine receptor expression increased in the bone marrow cells of EAM mice. Conclusions-TRX-1 attenuates EAM by suppressing chemokine expressions and leukocyte chemotaxis in mice.

In the endoplasmic reticulum (ER), a variety of oxidoreductases classified in the thioredoxin superfamily have been found to catalyze the formation and rearrangement of disulfide bonds. However, the precise function and specificity of the individual thioredoxin family proteins remain to be elucidated. Here, we characterize a transmembrane thioredoxinrelated protein (TMX), a membrane-bound oxidoreductase in the ER. TMX exists in a predominantly reduced form and associates with the molecular chaperon calnexin, which can mediate substrate binding. To determine the target molecules for TMX, we apply a substrate-trapping approach based on the reaction mechanism of thiol-disulfide exchange, identifying major histocompatibility complex (MHC) class I heavy chain (HC) as a candidate substrate. Unlike the classical ER oxidoreductases such as protein disulfide isomerase and ERp57, TMX seems not to be essential for normal assembly of MHC class I molecules. However, we show that TMX-class I HC interaction is enhanced during tunicamycin-induced ER stress, and TMX prevents the ER-to-cytosol retrotranslocation of misfolded class I HC targeted for proteasomal degradation. These results suggest a specific role for TMX and its mechanism of action in redox-based ER quality control. INTRODUCTIONMany secretory and membrane proteins are cotranslationally transported into the endoplasmic reticulum (ER), in which they acquire their correct conformation (Ellgaard and Helenius, 2003). The formation of disulfide bonds between cysteine residues is critical for the proper folding and assembly of proteins entering the secretory pathway (Sevier and Kaiser, 2006). The ER contains several oxidoreductases classified in the thioredoxin superfamily that catalyze the formation and rearrangement of disulfide bonds. Thioredoxin has been demonstrated to catalyze the reduction of disulfide bonds and thereby participate in many thiol-dependent cellular processes (Nakamura, 2005). Most of the ER oxidoreductases contain thioredoxin-like domains with their characteristic CXXC active site motifs that are responsible for catalyzing thiol-disulfide exchange reactions (Ellgaard and Ruddock, 2005).Although many ER oxidoreductases, such as protein disulfide isomerase (PDI) and ERp57, are soluble proteins in the ER lumen, there also exist several membrane-bound oxidoreductases. In a search for genes induced by transforming growth factor-␤, we identified a member of the thioredoxin family, transmembrane thioredoxin-related protein (TMX) (Akiyama et al., 2000;Matsuo et al., 2001). TMX contains one catalytic thioredoxin-like domain with a unique active site motif, CPAC, and a single transmembrane region. TMX orthologues have been found in other animal species, including mammals, Drosophila melanogaster, and Caenorhabditis elegans (Ko and Chow, 2002) but not in plants, fungi, or prokaryotes. The thioredoxin-like domain of TMX is present in the ER lumen and shows reductase and isomerase activity in vitro (Matsuo et al., 2004). TMX2 and TMX3 have also been reported in t...