Negative-High Titer of Helicobacter pylori Antibody and Lipid Profiles.

Background: Helicobacter pylori (HP) is a causative factor for several gastrointestinal diseases. A HP seropositive antibody titer (i.e., ≥10 U/mL), a threshold indicating an HP infection, is known to be associated with changes in lipid metabolism. There is evidence that HP infection can be found in some individuals with HP antibody titer of between 3 and 9.9 U/mL (termed as "negative-high titer"). However, it is unknown about the relationship between HP negative-high titer and lipid metabolism. The present study aimed to quantify the association between HP negative-high antibody titer and lipid profiles. Materials and Methods: We surveyed 2,478 people who underwent a Ningen Dock examination and had serological HP antibody data, from May 2016 to December 2020 at National Center for Global Health and Medicine, Tokyo, Japan. Multiple regression models were used to quantify the association between HP antibody titer and serum lipid levels. Results: The adjusted odds ratio (95% confidence interval [CI]) for dyslipidemia in HP negative-high and positive titer was 1.24 (0.96, 1.79) and 1.36 (1.10, 1.68), respectively, compared with HP negative-low titer; p trend =0.005. The adjusted mean (95% CI) of high-density lipoprotein cholesterol (HDL-C) in HP negative-low, negative-high, and positive titer was 58.78 (57.86-59.71), 55.30 (53.70-56.91), and 53.76 (52.90-54.63) mg/dL, respectively; p trend <0.001. Higher HP antibody titers were also associated with higher ratio of low-density lipoprotein cholesterol (LDL-C) to HDL-C, but not triglycerides, or total cholesterols. Conclusion: The present cross-sectional study suggests that a HP negative-high antibody titer may be associated with dyslipidemia, HDL-C, and LDL-C to HDL-C ratio among Japanese Ningen Dock's participants.

Analysis of the V2 Vasopressin Receptor (V2R) Mutations Causing Partial Nephrogenic Diabetes Insipidus Highlights a Sustainable Signaling by a Non-peptide V2R Agonist.

Disease-causing mutations in G protein-coupled receptor (GPCR) genes, including the V2 vasopressin receptor (V2R) gene, often cause misfolded receptors, leading to a defect in plasma membrane trafficking. A novel V2R mutation, T273M, identified in a boy with partial nephrogenic diabetes insipidus (NDI), shows intracellular localization and partial defects similar to the two mutants we described previously (10). Although non-peptide V2R antagonists have been shown to rescue the membrane localization of V2R mutants, their level of functional rescue is weak. Interestingly, it has been reported that a non-peptide agonist, OPC51803, activates misfolded V2R mutants intracellularly without degradation, thus potentially serving as a therapeutic agent against NDI (14). In our current experiments, however, a peptide antagonist blocked arginine vasopressin (AVP)- or OPC51803-stimulated cAMP accumulation both in COS-7 and MDCK cells, suggesting that OPC51803 mainly stimulates cell surface V2R mutants. In addition, our analyses revealed that OPC51803 works not only as a non-peptide agonist that causes activation/ß-arrestin-dependent desensitization of V2R mutants expressed at the plasma membrane but also as a pharmacochaperone that promotes the endoplasmic reticulum-retained mutant maturation and trafficking to the plasma membrane. The ratio of the pharmacochaperone effect to the desensitization effect likely correlates negatively with the residual function of the tested mutants, suggesting that OPC5 has a more favorable effect on the V2R mutants with a less residual function. We speculated that the canceling of the desensitization effect of OPC51803 by the pharmacochaperone effect after long-term treatment may produce sustainable signaling, and thus pharmacochaperone agonists such as OPC51803 may serve as promising therapeutics for NDI caused by misfolded V2R mutants.

Attenuated desensitization of ß-adrenergic receptor by water-soluble N-nitrosamines that induce S-nitrosylation without NO release.

RATIONALE: The clinical problem of loss of ß-adrenergic receptor (ß-AR) response, both in the pathogenesis of heart failure and during therapeutic application of ß-agonists, is attributable, at least in part, to desensitization, internalization, and downregulation of the receptors. In the regulation of ß-AR signaling, G protein-coupled receptor kinase 2 (GRK2) primarily phosphorylates agonist-occupied ß-ARs, and this modification promotes desensitization, internalization, and downregulation of ß-ARs. It has been demonstrated that GRK2 is inhibited by its S-nitrosylation. However, compounds that induce S-nitrosylation, such as S-nitrosoglutathione, simultaneously generate NO, which has been demonstrated to operate for cardiovascular protection. OBJECTIVE: We examine whether S-nitrosylation without NO generation inhibits desensitization of ß(2)-AR by GRK2. We thus aim to synthesize compounds that specifically induce S-nitrosylation. METHODS AND RESULTS: We have developed water-soluble N-nitrosamines that have S-nitrosylating activity but lack NO-generating activity. These compounds, at least partly, rescue ß-AR from desensitization in HEK 293 cells expressing FLAG-tagged human ß(2)-AR and in rat cardiac myocytes. They inhibit isoproterenol-dependent phosphorylation and internalization of ß(2)-AR. Indeed, they nitrosylate GRK2 in vitro and in cells, and their S-nitrosylation of GRK2 likely underlies their inhibition of ß(2)-AR desensitization. CONCLUSIONS: Compounds that induce S-nitrosylation without NO release inhibit GRK2 and attenuate ß(2)-AR desensitization. Developing water-soluble drugs that specifically induce S-nitrosylation may be a promising therapeutic strategy for heart failure.

V2 vasopressin receptor (V2R) mutations in partial nephrogenic diabetes insipidus highlight protean agonism of V2R antagonists.

Inactivating mutations of the V2 vasopressin receptor (V2R) cause cross-linked congenital nephrogenic diabetes insipidus (NDI), resulting in renal resistance to the antidiuretic hormone AVP. In two families showing partial NDI, characterized by an apparently normal response to diagnostic tests and an increase in the basal ADH levels suggesting AVP resistance, we have identified two V2R mutations, Ser-333del and Y128S. Both mutant V2Rs, when expressed in COS-7 cells, show partial defects in vasopressin-stimulated cAMP accumulation and intracellular localization. The inhibition of internalization does not rescue their localization. In contrast, the non-peptide V2R antagonists OPC41061 and OPC31260 partially rescue the membrane localization and basal function of these V2R mutants, whereas they inhibit the basal activity of the wild-type V2R. These results indicate that a partial loss of function of Ser-333del and Y128S mutant V2Rs results from defective membrane trafficking. These findings further indicate that V2R antagonists can act as protean agonists, serving as pharmacological chaperones for inactivating V2R mutants and also as inverse agonists of wild-type receptors. We speculate that this protean agonism could underlie the possible dual beneficial effects of the V2R antagonist: improvement of hyponatremia with heart failure or polycystic kidney disease and potential rescue of NDI.

Enzymatic actions of Pasteurella multocida toxin detected by monoclonal antibodies recognizing the deamidated α subunit of the heterotrimeric GTPase Gq.

Pasteurella multocida toxin (PMT) is a virulence factor responsible for the pathogenesis of some Pasteurellosis. PMT exerts its toxic effects through the activation of heterotrimeric GTPase (G(q), G(12/13) and G(i))-dependent pathways, by deamidating a glutamine residue in the α subunit of these GTPases. However, the enzymatic characteristics of PMT are yet to be analyzed in detail because the deamidation has only been observed in cell-based assays. In the present study, we developed rat monoclonal antibodies, specifically recognizing the deamidated Gα(q), to detect the actions of PMT by immunological techniques such as western blotting. Using the monoclonal antibodies, we found that the toxin deamidated Gα(q) only under reducing conditions. The C-terminal region of PMT, C-PMT, was more active than the full-length PMT. The C3 domain possessing the enzyme core catalyzed the deamidation in vitro without any other domains. These results not only support previous observations on toxicity, but also provide insights into the enzymatic nature of PMT. In addition, we present several lines of evidence that Gα(11), as well as Gα(q), could be a substrate for PMT.

Human G(salpha) mutant causes pseudohypoparathyroidism type Ia/neonatal diarrhea, a potential cell-specific role of the palmitoylation cycle.

Pseudohypoparathyroidism type Ia (PHP-Ia) results from the loss of one allele of G(salpha), causing resistance to parathyroid hormone and other hormones that transduce signals via G(s). Most G(salpha)mutations cause the complete loss of protein expression, but some cause loss of function only, and these have provided valuable insights into the normal function of G proteins. Here we have analyzed a mutant G(salpha) (alphas-AVDT) harboring AVDT amino acid repeats within its GDP/GTP binding site, which was identified in unique patients with PHP-Ia accompanied by neonatal diarrhea. Biochemical and intact cell analyses showed that alphas-AVDT is unstable but constitutively active as a result of rapid GDP release and reduced GTP hydrolysis. This instability underlies the PHP-Ia phenotype. alphas-AVDT is predominantly localized in the cytosol, but in rat and mouse small intestine epithelial cells (IEC-6 and DIF-12 cells) alphas-AVDT was found to be localized predominantly in the membrane where adenylyl cyclase is present and constitutive increases in cAMP accumulation occur in parallel. The likely cause of this membrane localization is the inhibition of an activation-dependent decrease in alphas palmitoylation. Upon the overexpression of acyl-protein thioesterase 1, however, alphas-AVDT translocates from the membrane to the cytosol, and the constitutive accumulation of cAMP becomes attenuated. These results suggest that PHP-Ia results from the instability of alphas-AVDT and that the accompanying neonatal diarrhea may result from its enhanced constitutive activity in the intestine. Hence, palmitoylation may control the activity and localization of G(salpha) in a cell-specific manner.

Liquid crystal formation of RecA-DNA filamentous complexes.

Spontaneous optical birefringence of RecA-bound linear and closed circular single-stranded DNA filaments, as well as RecA self-assembled polymer, was observed in aqueous buffer solutions, which demonstrates the formation of lyotropic liquid crystalline phases.

An acquired hypocalciuric hypercalcemia autoantibody induces allosteric transition among active human Ca-sensing receptor conformations.

The seven-spanning calcium-sensing receptor (CaSR) activates multiple G proteins including Gq and Gi, and thereby activates a variety of second messengers and inhibits parathyroid hormone (PTH) secretion. However, the exact signaling mechanisms underlying the functional activity of CaSR are not yet fully understood. The heterozygous inactivation of CaSR or its inhibition by antibody blocking results in either familial hypocalciuric hypercalcemia or acquired hypocalciuric hypercalcemia (AHH), respectively. Here, we report the identification of a unique CaSR autoantibody in an AHH patient. Paradoxically, we find that this autoantibody potentiates the Ca(2+)/Gq-dependent accumulation of inositol phosphates by slightly shifting the dose dependence curve of the Ca(2+) mediated activation of phosphatidylinositol turnover to the left, whereas it inhibits the Ca(2+)/Gi-dependent phosphorylation of ERK1/2 in HEK293 cells stably expressing human CaSR. Treatment of these same cells with a calcimimetic, NPS-R-568, augments the CaSR response to Ca(2+), increasing phosphatidylinositol turnover and ERK1/2 phosphorylation, and overcoming the autoantibody effects. Our observations thus indicate that a calcium-stimulated CaSR primed by a specific autoantibody adopts a unique conformation that activates Gq but not Gi. Our findings also suggest that CaSR signaling may act via both Gq and Gi to inhibit PTH secretion. This is the first report of a disease-related autoantibody that functions as an allosteric modulator and maintains G protein-coupled receptors (GPCRs) in a unique active conformation with its agonist. We thus speculate that physiological modulators may exist that enable an agonist to specifically activate only one signaling pathway via a GPCR that activates multiple signaling pathways.

Visualization of RecA filaments and DNA by fluorescence microscopy.

We have developed two experimental methods for observing Escherichia coli RecA-DNA filament under a fluorescence microscope. First, RecA-DNA filaments were visualized by immunofluorescence staining with anti-RecA monoclonal antibody. Although the detailed filament structures below submicron scale were unable to be measured accurately due to optical resolution limit, this method has an advantage to analyse a large number of RecA-DNA filaments in a single experiment. Thus, it provides a reliable statistical distribution of the filament morphology. Moreover, not only RecA filament, but also naked DNA region was visualized separately in combination with immunofluorescence staining using anti-DNA monoclonal antibody. Second, by using cysteine derivative RecA protein, RecA-DNA filament was directly labelled by fluorescent reagent, and was able to observe directly under a fluorescence microscope with its enzymatic activity maintained. We showed that the RecA-DNA filament disassembled in the direction from 5' to 3' of ssDNA as dATP hydrolysis proceeded.

Conductive metal nanowires templated by the nucleoprotein filaments, complex of DNA and RecA protein.

Development of preprogrammable conductive nanowires is a requisite for the future fabrication of nanoscale electronics based on molecular assembly. Here, we report the synthesis of conductive metal nanowires from nucleoprotein filaments, complexes of single- or double-stranded DNA and RecA protein. A genetically engineered RecA derivative possessing a reactive and surface accessible cysteine residue was reacted with functionalized gold particles, resulting in nucleoprotein filaments with gold particles attached. The template-based gold particles were enlarged by chemical deposition to form uniformly metallized nanowires. The programming information can be encoded in DNA sequences so that an intricate electrical circuit can be constructed through self-assembly of each component. As the RecA filament has higher degree of stiffness than double-stranded DNA, it provides a robust scaffold that allows us to fabricate more reliable and well-organized electrical circuitry at the nanoscale. Furthermore, the function of homologous pairing provides sequence-specific junction formation as well as sequence-specific patterning metallization.

Redox behavior of ferrocene-containing rotaxane: transposition of the rotaxane wheel by redox reaction of a ferrocene moiety tethered at the end of the axle.

A rotaxane with a ferrocene moiety at the axle terminus was prepared. The redox potential of the ferrocene moiety decreased by ca. 80 mV when the rotaxane had a crown ether wheel capable of moving on the axle. Thus, the stabilization of the oxidized state of the ferrocene moiety is assumed to accompany the transposition of the wheel component on the axle toward the ferrocene moiety. [reaction--see text]

Mechanisms responsible for delayed and immediate hemolytic transfusion reactions in a patient with anti-E + Jk(b)+ Di(b) and anti-HLA alloantibodies.

Immediate hemolytic transfusion reactions (IHTR) occurred in the course of delayed hemolytic transfusion reactions (DHTR). An 84-year-old man had received a blood transfusion 20 years ago. Progressive anemia developed, because of continuous bleeding from a bladder tumor. He was transfused with concentrated red blood cells (CRC) which were Rh-E antigen negative, because he had anti-E antibodies (day 0). He received CRC on day 3, and underwent resection of bladder tumor on day 6. Although crossmatch-compatible CRCs were prepared for the operation, those were not required and were kept in a refrigerator in the ward. On day 9, when a CRC kept in the ward was transfused, he suddenly had a IHTR. In order to analyze a mechanism of IHTR, the anti-Jk(b) and anti-Di(b) antibodies, anti-HLA antibodies and the concentrations of inflammatory cytokines were measured in serum samples. The anti-Jk(b) and anti-Di(b) antibodies increased prior to IHTR experienced on day 9. The concentrations of IL-6 and IL-1beta increased from day 2, while the concentration of IL-8 increased from day 7. The anti-HLA class I antibody could be detected 2 days before IHTR. Thus, the anti-Jk(b) and anti-Di(b) antibodies induced the production of inflammatory cytokines and symptoms of DHTR and IHTR. The anti-HLA class I antibody could be produced in spite of using the filer for removing leukocytes, and may take part in the induction of IHTR. Further, blood products should be transfused soon after completing a crossmatch test in patients with anti-RBC alloantibodies.