Enhancing extracellular membrane vesicle productivity of Shewanella vesiculosa HM13, a prospective host for vesiculation-mediated protein secretion, by weakening outer membrane-peptidoglycan linkage

Shewanella vesiculosa HM13, a psychrotrophic gram-negative bacterium isolated from the intestinal contents of horse mackerel, produces abundant extracellular membrane vesicles (EMVs) by budding the outer membrane. The EMVs of this bacterium carry a single major cargo protein, P49, of unknown function, which may be useful as a carrier for the secretory production of heterologous proteins as cargoes of EMVs. In this study, to increase the utility of S. vesiculosa HM13 as a host for EMV-mediated protein production, we improved its EMV productivity by weakening the linkage between the outer membrane and underlying peptidoglycan layer. In gram-negative bacteria, the outer membrane is connected to peptidoglycans predominantly through Braun's lipoprotein (Lpp), and the formation of this linkage is catalyzed by an l,d-transpeptidase (Ldt). We constructed gene-disrupted mutants of Lpp and Ldt and assessed their EMV productivity. The EMVs of the lpp- and ldt-disrupted mutants grown at 18 °C were evaluated using nanoparticle tracking analysis, and their morphologies were observed using transmission electron microscopy. As a result, an approximately 2.5-fold increase in EMV production was achieved, whereas the morphology of the EMVs of these mutants remained almost identical to that of the parent strain. In accordance with the increase in EMV production, the mutants secreted approximately 2-fold higher amounts of P49 than the parent strain into the culture broth as the EMV cargo. These findings will contribute to the development of an EMV-based secretory production system for heterologous proteins using S. vesiculosa HM13 as a host.

Structural study of a polysaccharide component of nfnB mutant of Shewanella vesiculosa HM13

Shewanella vesiculosa HM13 is a Gram-negative bacterium able to produce a large amount of extracellular membrane vesicles. These nanoparticles carry a major protein P49, the loading of which seems to be influenced by the glycans decorating the membrane. Here we report the structural characterization, using chemical analyses and NMR spectroscopy, of the capsular polysaccharides isolated from the nfnB-mutant strain of S. vesiculosa HM13, which is unable to load P49 on the membrane vesicles. In addition to the polysaccharide corona isolated and characterized from the parental strain, the nfnB-mutant strain released another polysaccharide composed of disaccharide repeating units having the following structure. →4)-β-D-Glc-(1 → 3)-β-D-GlcNAc-(1→.

Risk factors for postoperative nausea and vomiting after video-assisted thoracic surgery esophagectomy: a prospective cohort study

Video-assisted thoracic surgery esophagectomy (VATS-E) may increase the risk of postoperative nausea and vomiting (PONV) because it uses a high dosage of anesthesia through a long operative duration. However, no study has examined the risk factors for PONV after VATS-E. Therefore, we investigated the risk factors for PONV to support the appropriate risk management of PONV after VATS-E. This prospective cohort study included 155 patients who underwent VATS-E at the Showa University Hospital between April 1st, 2020 and November 30th, 2022. The primary outcome was the incidence of PONV within 24 h after surgery. Significant independent risk factors associated with the incidence of PONV were selected using multivariate analysis. The association between the number of risk factors for PONV and incidence of PONV was analyzed. One-hundred fifty-three patients were included in the analysis. The patients' median age was 67 years (range, 44-88), and 79.1% were male. PONV occurred in 35 (22.9%) patients. In the multivariate analysis, remifentanil dosage > 89.0 ng/kg/ min, albumin ≤ 3.5 g/dL, and eGFR < 60 mL/min/1.73 m 2 were independent significant risk factors for PONV. A significant association was observed between the incidence of and the number of risk factors for PONV (0 factor, 5.8%; 1 factor, 27.3%; ≥ 2 factors, 40.0%; p = 0.001). These three risk factors are useful indicators for selecting patients at high risk of developing PONV after VATS-E. In these patients, avoiding the development of PONV will be possible by performing appropriate risk management.

Discovery of ultrafast spontaneous spin switching in an antiferromagnet by femtosecond noise correlation spectroscopy

Owing to their high magnon frequencies, antiferromagnets are key materials for future high-speed spintronics. Picosecond switching of antiferromagnetic spin systems has been viewed a milestone for decades and pursued only by using ultrafast external perturbations. Here, we show that picosecond spin switching occurs spontaneously due to thermal fluctuations in the antiferromagnetic orthoferrite Sm0.7Er0.3FeO3. By analysing the correlation between the pulse-to-pulse polarisation fluctuations of two femtosecond optical probes, we extract the autocorrelation of incoherent magnon fluctuations. We observe a strong enhancement of the magnon fluctuation amplitude and the coherence time around the critical temperature of the spin reorientation transition. The spectrum shows two distinct features, one corresponding to the quasi-ferromagnetic mode and another one which has not been previously reported in pump-probe experiments. Comparison to a stochastic spin dynamics simulation reveals this new mode as smoking gun of ultrafast spontaneous spin switching within the double-well anisotropy potential.

Structural factors governing binding of curvature-sensing peptides to bacterial extracellular vesicles covered with hydrophilic polysaccharide chains

Extracellular vesicles (EVs) have attracted an attention as important targets in the fields of biology and medical science because they contain physiologically active molecules. Curvature-sensing peptides are currently used as novel tools for marker-independent EV detection techniques. A structure-activity correlation study demonstrated that the α-helicity of the peptides is prominently involved in peptide binding to vesicles. However, whether a flexible structure changing from a random coil to an α-helix upon binding to vesicles or a restricted α-helical structure is an important factor in the detection of biogenic vesicles is still unclear. To address this issue, we compared the binding affinities of stapled and unstapled peptides for bacterial EVs with different surface polysaccharide chains. We found that unstapled peptides showed similar binding affinities for bacterial EVs regardless of surface polysaccharide chains, whereas stapled peptides showed substantially decreased binding affinities for bacterial EVs covered with capsular polysaccharides. This is probably because curvature-sensing peptides must pass through the layer of hydrophilic polysaccharide chains prior to binding to the hydrophobic membrane surface. While stapled peptides with restricted structures cannot easily pass through the layer of polysaccharide chains, unstapled peptides with flexible structures can easily approach the membrane surface. Therefore, we concluded that the structural flexibility of curvature-sensing peptides is a key factor for governing the highly sensitive detection of bacterial EVs.

Associations of time to return to performance following acute posterior thigh injuries with running biomechanics, hamstring function, and structure in collegiate sprinters: A prospective cohort design

BACKGROUND

The time to return to sport from acute hamstring strain injuries is associated with several functional and structural impairments. However, not all previous studies assessed the preinjury level before acute hamstring strain injuries directly. The purpose of this study was to examine the associations of the time to return to performance following acute hamstring strain injuries with deficits in running biomechanics, hamstring function and structure in collegiate sprinters by a prospective study.

METHODS

Using a prospective cohort design, 72 participants were recruited from a collegiate track and field team. At the preinjury assessment, a 60-m running-specific test, passive straight leg raise test and isometric knee flexion strength test were assessed at the beginning of the competitive season for three consecutive years (2017-2019). Afterwards, postinjury examinations were performed only in sprinters with acute hamstring strain injuries.

FINDINGS

Twelve sprinters strained their hamstring muscle (incidence rate of hamstring strain injuries: 16.7%); the majority (n = 10) were classified as grades 0-2. The running speed deficit of the running-specific test was associated with the time to return to performance as well as the passive straight leg raise test deficit. In the running-specific test, lower-limb kinetic deficits were more strongly associated with the time to return to performance compared to lower-limb kinematic deficits.

INTERPRETATION

A running-specific test may be considered one of the most convenient and valid tests for assessing rehabilitation progress after acute hamstring strain injuries.

Division of the role and physiological impact of multiple lysophosphatidic acid acyltransferase paralogs

Background

Lysophosphatidic acid acyltransferase (LPAAT) is a phospholipid biosynthesis enzyme that introduces a particular set of fatty acids at the sn-2 position of phospholipids. Many bacteria have multiple LPAAT paralogs, and these enzymes are considered to have different fatty acid selectivities and to produce diverse phospholipids with distinct fatty acid compositions. This feature is advantageous for controlling the physicochemical properties of lipid membranes to maintain membrane integrity in response to the environment. However, it remains unclear how LPAAT paralogs are functionally differentiated and biologically significant.

Results

To better understand the division of roles of the LPAAT paralogs, we analyzed the functions of two LPAAT paralogs, PlsC4 and PlsC5, from the psychrotrophic bacterium Shewanella livingstonensis Ac10. As for their enzymatic function, lipid analysis of plsC4- and plsC5-inactivated mutants revealed that PlsC4 prefers iso-tridecanoic acid (C₁₂-chain length, methyl-branched), whereas PlsC5 prefers palmitoleic acid (C₁₆-chain length, monounsaturated). Regarding the physiological role, we found that plsC4, not plsC5, contributes to tolerance to cold stress. Using bioinformatics analysis, we demonstrated that orthologs of PlsC4/PlsC5 and their close relatives, constituting a new clade of LPAATs, are present in many γ-proteobacteria. We also found that LPAATs of this clade are phylogenetically distant from principal LPAATs, such as PlsC1 of S. livingstonensis Ac10, which are universally conserved among bacteria, suggesting the presence of functionally differentiated LPAATs in these bacteria.

Conclusions

PlsC4 and PlsC5, which are LPAAT paralogs of S. livingstonensis Ac10, play different roles in phospholipid production and bacterial physiology. An enzyme belonging to PlsC4/PlsC5 subfamilies and their close relatives are present, in addition to principal LPAATs, in many γ-proteobacteria, suggesting that the division of roles is more common than previously thought. Thus, both principal LPAATs and PlsC4/PlsC5-related enzymes should be considered to decipher the metabolism and physiology of bacterial cell membranes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02641-8.

Effects of prior osteoporosis treatment on the treatment response of romosozumab followed by denosumab in patients with postmenopausal osteoporosis

In patients with postmenopausal osteoporosis, prior osteoporosis treatment affected the bone mineral density increase of following treatment with 12 months of romosozumab, although it did not affect that of following treatment with 12 months of denosumab after romosozumab.

PURPOSE

To investigate the effects of prior osteoporosis treatment on the response to treatment with romosozumab (ROMO) followed by denosumab (DMAb) in patients with postmenopausal osteoporosis.

METHODS

In this prospective, observational, multicenter study, treatment-naïve patients (Naïve; n = 55) or patients previously treated with bisphosphonates (BP; n = 37), DMAb (DMAb; n = 45) or teriparatide (TPTD; n = 17) (mean age, 74.6 years; T-scores of the lumbar spine [LS] - 3.2 and total hip [TH] - 2.6) were switched to ROMO for 12 months, followed by DMAb for 12 months. Bone mineral density (BMD) and serum bone turnover markers were evaluated for 24 months.

RESULTS

A BMD increase was observed at 12 and 24 months in the following patients: Naïve (18.2% and 22.0%), BP (10.2% and 12.1%), DMAb (6.6% and 9.7%), and TPTD (10.8% and 15.0%) (P < 0.001 between the groups at both 12 and 24 months) in LS and Naïve (5.5% and 8.3%), BP (2.9% and 4.1%), DMAb (0.6% and 2.2%), and TPTD (4.3% and 5.4%) (P < 0.01 between the groups at 12 months and P < 0.001 at 24 months) in TH, respectively. The BMD increase in LS from 12 to 24 months was negatively associated with the levels of bone resorption marker at 24 months. Incidences of major fragility fractures for the respective groups were as follows: Naïve (5.5%), BP (16.2%), DMAb (11.1%), and TPTD (5.9%).

CONCLUSIONS

Previous treatment affected the BMD increase of following treatment with ROMO, although it did not affect that of following treatment with DMAb after ROMO.

Capsular polysaccharide from a fish-gut bacterium induces/promotes apoptosis of colon cancer cells in vitro through Caspases' pathway activation

Among the widespread malignancies colorectal cancer is the most lethal. Treatments of this malignant tumor include surgery for lesions and metastases, radiotherapy, immunotherapy, and chemotherapy. Nevertheless, novel therapies to reduce morbidity and mortality are demanding. Natural products, such as polysaccharides, can be a valuable alternative to sometimes very toxic chemotherapeutical agents, also because they are biocompatible and biodegradable biomaterials. Microbial polysaccharides have been demonstrated to fulfill this requirement. In this paper, the results about the structure and the activity of a capsular polysaccharide isolated from the psychrotroph Pseudoalteromonas nigrifaciens Sq02-Rif^r, newly isolated from the fish intestine, have been described. The characterization has been obtained by spectroscopic and chemical methods, and it is supported by the bioinformatic analysis. The polymer activates Caspases 3 and 9 on colon cancer cells CaCo-2 and HCT-116, indicating a promising antitumor effect, and suggesting a potential capacity of CPS to induce apoptosis.

Design of the N-Terminus Substituted Curvature-Sensing Peptides That Exhibit Highly Sensitive Detection Ability of Bacterial Extracellular Vesicles

Extracellular vesicles (EVs) have emerged as important targets in biological and medical studies because they are involved in diverse human diseases and bacterial pathogenesis. Although antibodies targeting the surface biomarkers are widely used to detect EVs, peptide-based curvature sensors are currently attracting an attention as a novel tool for marker-free EV detection techniques. We have previously created a curvature-sensing peptide, FAAV and applied it to develop a simple and rapid method for detection of bacterial EVs in cultured media. The method utilized the fluorescence/Förster resonance energy transfer (FRET) phenomenon to achieve the high sensitivity to changes in the EV amount. In the present study, to develop a practical and easy-to-use approach that can detect bacterial EVs by peptides alone, we designed novel curvature-sensing peptides, N-terminus-substituted FAAV (nFAAV) peptides. The nFAAV peptides exerted higher α-helix-stabilizing effects than FAAV upon binding to vesicles while maintaining a random coil structure in aqueous solution. One of the nFAAV peptides showed a superior binding affinity for bacterial EVs and detected changes in the EV amount with 5-fold higher sensitivity than FAAV even in the presence of the EV-secretory bacterial cells. We named nFAAV5, which exhibited the high ability to detect bacterial EVs, as an EV-sensing peptide. Our finding is that the coil-α-helix structural transition of the nFAAV peptides serve as a key structural factor for highly sensitive detection of bacterial EVs.

Initial Step of Selenite Reduction via Thioredoxin for Bacterial Selenoprotein Biosynthesis

Many organisms reductively assimilate selenite to synthesize selenoprotein. Although the thioredoxin system, consisting of thioredoxin 1 (TrxA) and thioredoxin reductase with NADPH, can reduce selenite and is considered to facilitate selenite assimilation, the detailed mechanism remains obscure. Here, we show that selenite was reduced by the thioredoxin system from Pseudomonas stutzeri only in the presence of the TrxA (PsTrxA), and this system was specific to selenite among the oxyanions examined. Mutational analysis revealed that Cys33 and Cys36 residues in PsTrxA are important for selenite reduction. Free thiol-labeling assays suggested that Cys33 is more reactive than Cys36. Mass spectrometry analysis suggested that PsTrxA reduces selenite via PsTrxA-SeO intermediate formation. Furthermore, an in vivo formate dehydrogenase activity assay in Escherichia coli with a gene disruption suggested that TrxA is important for selenoprotein biosynthesis. The introduction of PsTrxA complemented the effects of TrxA disruption in E. coli cells, only when PsTrxA contained Cys33 and Cys36. Based on these results, we proposed the early steps of the link between selenite and selenoprotein biosynthesis via the formation of TrxA–selenium complexes.

Identification of a Putative Sensor Protein Involved in Regulation of Vesicle Production by a Hypervesiculating Bacterium, Shewanella vesiculosa HM13

Bacteria secrete and utilize nanoparticles, called extracellular membrane vesicles (EMVs), for survival in their growing environments. Therefore, the amount and components of EMVs should be tuned in response to the environment. However, how bacteria regulate vesiculation in response to the extracellular environment remains largely unknown. In this study, we identified a putative sensor protein, HM1275, involved in the induction of vesicle production at high lysine concentration in a hypervesiculating Gram-negative bacterium, Shewanella vesiculosa HM13. This protein was predicted to possess typical sensing and signaling domains of sensor proteins, such as methyl-accepting chemotaxis proteins. Comparison of vesicle production between the hm1275-disrupted mutant and the parent strain revealed that HM1275 is involved in lysine-induced hypervesiculation. Moreover, HM1275 has sequence similarity to a biofilm dispersion protein, BdlA, of Pseudomonas aeruginosa PAO1, and hm1275 disruption increased the amount of biofilm. Thus, this study showed that the induction of vesicle production and suppression of biofilm formation in response to lysine concentration are under the control of the same putative sensor protein.

Development of a Simple and Rapid Method for In Situ Vesicle Detection in Cultured Media

Extracellular membrane vesicles (EMVs) are biogenic secretory lipidic vesicles that play significant roles in intercellular communication related to human diseases and bacterial pathogenesis. They are being investigated for their possible use in diagnosis, vaccines, and biotechnology. However, the existing methods suffer from a number of issues. High-speed centrifugation, a widely used method to collect EMVs, may cause structural artifacts. Immunostaining methods require several steps and thus the separation and detection of EMVs from the secretory cells is time-consuming. Furthermore, detection of EMVs using these methods requires specific and costly antibodies. To tackle these problems, development of a simple and rapid detection method for the EMVs in the cultured medium without separation from the secretory cells is a pressing task. In this study, we focused on the Gram-negative bacterium Shewanella vesiculosa HM13, which produces a large amount of EMVs including a cargo protein with high purity, as a model. Curvature-sensing peptides were used for EMV-detection tools. FAAV, a peptide derived from sorting nexin protein 1, selectively binds to the EMVs even in the presence of the secretory cells in the complex cultured medium. FAAV can fully detect the EMVs within a few minutes, and the resistance of FAAV to proteases enables it to withstand prolonged use in the cultured medium. Fluorescence/Förster resonance energy transfer was used to develop a method to detect changes in the amount of the EMVs with high sensitivity. Overall, our results indicate the potential applicability of FAAV for in situ EMV detection in cultured media.

C-reactive protein : albumin ratio in patients with resectable intrahepatic cholangiocarcinoma

BACKGROUND

The C-reactive protein : albumin ratio (CAR) has been reported as a novel prognostic marker in several cancers. The aim of this study was to investigate the prognostic value of CAR in patients with intrahepatic cholangiocarcinoma (ICC).

METHODS

This was a single-centre retrospective study of patients who underwent surgery for ICC in a university hospital in Japan between 1998 and 2018. CAR, Glasgow Prognostic Score (GPS) and modified GPS (mGPS) were calculated. Their correlation with recurrence-free survival (RFS) and overall survival (OS) was analysed with Cox proportional hazards models.

RESULTS

Seventy-two patients were included in the study. Patients were divided into two groups according to the optimal CAR cut-off value of 0·02. CAR above 0·02 was associated with higher carbohydrate antigen 19-9 levels (20·5 versus 66·1 units/ml for CAR of 0·02 or less; P = 0·002), larger tumour size (3·2 versus 4·4 cm respectively; P = 0·031) and a higher rate of microvascular invasion (9 of 28 versus 25 of 44; P = 0·041). RFS and OS were shorter in patients with CAR above 0·02: hazard ratio (HR) 4·31 (95 per cent c.i. 2·02 to 10·63) and HR 4·80 (1·85 to 16·40) respectively. In multivariable analysis CAR above 0·02 was an independent prognostic factor of RFS (HR 3·29 (1·33 to 8·12); P < 0·001), but not OS.

CONCLUSIONS

CAR was associated with prognosis in patients who had hepatic resection for ICC.

Characterization of a novel class of glyoxylate reductase belonging to the β-hydroxyacid dehydrogenase family in Acetobacter aceti

Enzymes related to β-hydroxyacid dehydrogenases/3-hydroxyisobutyrate dehydrogenases are ubiquitous, but most of them have not been characterized. An uncharacterized protein with moderate sequence similarities to Gluconobacter oxydans succinic semialdehyde reductase and plant glyoxylate reductases/succinic semialdehyde reductases was found in the genome of Acetobacter aceti JCM20276. The corresponding gene was cloned and expressed in Escherichia coli. The gene product was purified and identified as a glyoxylate reductase that exclusively catalyzed the NAD(P)H-dependent reduction of glyoxylate to glycolate. The strict substrate specificity of this enzyme to glyoxylate, the diverged sequence motifs for its binding sites with cofactors and substrates, and its phylogenetic relationship to homologous enzymes suggested that this enzyme represents a novel class of enzymes in the β-hydroxyacid dehydrogenase family. This study may provide an important clue to clarify the metabolism of glyoxylate in bacteria. Abbreviations: GR: glyoxylate reductase; GRHPR: glyoxylate reductase/hydroxypyruvate reductase; HIBADH: 3-hydroxyisobutyrate dehydrogenase; SSA: succinic semialdehyde; SSAR: succinic semialdehyde reductase.

Lysophosphatidic acid acyltransferase from the thermophilic bacterium Thermus thermophilus HB8 displays substrate promiscuity

Lysophosphatidic acid acyltransferase is a phospholipid biosynthetic enzyme that introduces a fatty acyl group into the sn-2 position of phospholipids. Its substrate selectivity is physiologically important in defining the physicochemical properties of lipid membranes and modulating membrane protein function. However, it remains unclear how these enzymes recognize various fatty acids. Successful purification of bacterial lysophosphatidic acid acyltransferases (PlsCs) was recently reported and has paved a path for the detailed analysis of their reaction mechanisms. Here, we purified and characterized PlsC from the thermophilic bacterium Thermus thermophilus HB8. This integral membrane protein remained active even after solubilization and purification and showed reactivity toward saturated, unsaturated, and methyl-branched fatty acids, although branched-chain acyl groups are the major constituent of phospholipids of this bacterium. Multiple sequence alignment revealed the N-terminal end of the enzyme to be shorter than that of PlsCs with defined substrate selectivity, suggesting that the shortened N-terminus confers substrate promiscuity.

ABBREVIATIONS

ACP: acyl carrier protein; CAPS: N-cyclohexyl-3-aminopropanesulfonic acid; CoA: coenzyme A; CYMAL-6: 6-cyclohexyl-1-hexyl-β-D-maltoside; DDM: n-dodecyl-β-D-maltoside; DTNB: 5,5´-dithiobis(2-nitrobenzoic acid); EPA: eicosapentaenoic acid; G3P: glycerol 3-phosphate; HEPES: N-2-hydroxyethylpiperazine-N´-2-ethanesulfonic acid; LPA: lysophosphatidic acid; MS: mass spectrometry; PA: phosphatidic acid.

Bioconversion From Docosahexaenoic Acid to Eicosapentaenoic Acid in the Marine Bacterium Shewanella livingstonensis Ac10

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which belong to the same class of long chain ω-3 polyunsaturated fatty acids (PUFAs), are present in marine γ-proteobacteria. In contrast to their de novo biosynthesis that has been intensively studied, their metabolic fates remain largely unknown. Detailed information regarding bacterial ω-3 PUFA metabolism would be beneficial for understanding the physiological roles of EPA/DHA as well as the industrial production of EPA, DHA, and other PUFAs. Our previous studies revealed that the EPA-producing marine bacterium Shewanella livingstonensis Ac10 produces EPA from exogenous DHA independently of de novo EPA biosynthesis, indicating the presence of an unidentified metabolic pathway that converts DHA into EPA. In this study, we attempted to reveal the molecular basis for the bioconversion through both in vivo and in vitro analyses. Mutagenesis experiments showed that the gene disruption of fadH, which encodes an auxiliary β-oxidation enzyme 2,4-dienoyl-CoA reductase, impaired EPA production under DHA-supplemented conditions, and the estimated conversion rate decreased by 86% compared to that of the parent strain. We also found that the recombinant FadH had reductase activity toward the 2,4-dienoyl-CoA derivative of DHA, whereas the intermediate did not undergo β-oxidation in the absence of the FadH protein. These results indicate that a typical β-oxidation pathway is responsible for the conversion. Furthermore, we assessed whether DHA can act as a substitute for EPA by using an EPA-less and conversion-deficient mutant. The cold-sensitive phenotype of the mutant, which is caused by the lack of EPA, was suppressed by supplementation with EPA, whereas the DHA-supplementation suppressed it to a lesser extent. Therefore, DHA can partly substitute for, but is not biologically equivalent to, EPA in S. livingstonensis Ac10.

Effects of a pyroglutamyl pentapeptide isolated from fermented barley extract on atopic dermatitis-like skin lesions in hairless mouse

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritic and eczematous skin lesions. The skin of AD patients is generally in a dried condition. Therefore, it is important for AD patients to manage skin moisturization. In this study, we examined the effects of orally administered fermented barley extract P (FBEP), which is prepared from a supernatant of barley shochu distillery by-product, on stratum corneum (SC) hydration and transepidermal water loss (TEWL) in AD-like lesions induced in hairless mice using 2,4,6-trinitrochlorobenzene. Oral administration of FBEP increased SC hydration and decreased TEWL in the dorsal skin of this mouse model. Further fractionation of FBEP showed that a pyroglutamyl pentapeptide, pEQPFP comprising all -L-form amino acids, is responsible for these activities. These results suggested that this pyroglutamyl pentapeptide may serve as a modality for the treatment of AD.

A Novel Lysophosphatidic Acid Acyltransferase of Escherichia coli Produces Membrane Phospholipids with a cis-vaccenoyl Group and Is Related to Flagellar Formation

Lysophosphatidic acid acyltransferase (LPAAT) introduces fatty acyl groups into the sn-2 position of membrane phospholipids (PLs). Various bacteria produce multiple LPAATs, whereas it is believed that Escherichia coli produces only one essential LPAAT homolog, PlsC-the deletion of which is lethal. However, we found that E. coli possesses another LPAAT homolog named YihG. Here, we show that overexpression of YihG in E. coli carrying a temperature-sensitive mutation in plsC allowed its growth at non-permissive temperatures. Analysis of the fatty acyl composition of PLs from the yihG-deletion mutant (∆yihG) revealed that endogenous YihG introduces the cis-vaccenoyl group into the sn-2 position of PLs. Loss of YihG did not affect cell growth or morphology, but ∆yihG cells swam well in liquid medium in contrast to wild-type cells. Immunoblot analysis showed that FliC was highly expressed in ∆yihG cells, and this phenotype was suppressed by expression of recombinant YihG in ∆yihG cells. Transmission electron microscopy confirmed that the flagellar structure was observed only in ∆yihG cells. These results suggest that YihG has specific functions related to flagellar formation through modulation of the fatty acyl composition of membrane PLs.

Seventeen-year clinical outcome of schizophrenia in Bali

Objective

To examine the 17-year clinical outcome of schizophrenia and its predictors in Bali.

Methods

Subjects were 59 consecutively admitted first-episode schizophrenia patients. Their clinical outcome was evaluated by standardized symptomatic remission criteria based on Positive and Negative Syndrome Scale (PANSS) scores and operational functional remission criteria at 17-year follow-up. The standardized mortality ratio (SMR) over 17 years was also calculated as another index of clinical outcome.

Results

Among these 59 patients, 43 (72.9%) could be followed-up, 15 (25.4%) had died, and one (1.7%) was alive but refused to participate in the study. Combined remission (i.e. symptomatic and functional remission) was achieved in 14 patients (23.7% of original sample). Duration of untreated psychosis (DUP) was a significant baseline predictor of combined remission. Mean age at death of deceased subjects was 35.7, and SMR was 4.85 (95% CI: 2.4–7.3), indicating that deaths were premature. Longer DUP was associated with excess mortality.

Conclusions

The long-term outcome of schizophrenia in Bali was heterogeneous, demonstrating that a quarter achieved combined remission, half were in nonremission, and a quarter had died at 17-year follow-up. DUP was a significant predictor both for combined remission and mortality.

Genetic characterization and functional implications of the gene cluster for selective protein transport to extracellular membrane vesicles of Shewanella vesiculosa HM13

A hyper-vesiculating Gram-negative bacterium, Shewanella vesiculosa HM13, secretes a protein of unknown function (P49) as a major cargo of the extracellular membrane vesicles (EMVs). Here, we analyzed the transport mechanism of P49 to EMVs. The P49 gene is found in a gene cluster containing the genes encoding homologs of surface glycolipid biosynthesis proteins (Wza, WecA, LptA, and Wzx), components of type II secretion system (T2SS), glycerophosphodiester phosphodiesterase (GdpD), and nitroreductase (NfnB). We disrupted the genes in this cluster and analyzed the productivity and morphology of EMVs and the localization of P49. EMV production and morphology were only moderately affected by gene disruption, demonstrating that these gene products are not essential for EMV synthesis. In contrast, the localization of P49 was significantly affected by gene disruption. The lack of homologs of the T2SS components resulted in deficiency in secretion of P49. When gdpD, wzx, lptA, and nfnB were disrupted, P49 was released to the extracellular space without being loaded to the EMVs. These results suggest that P49 is translocated across the outer membrane through the T2SS-like machinery and subsequently loaded onto EMVs through interaction with surface glycolipids of EMVs.

Isolation of a Novel Bacterial Strain Capable of Producing Abundant Extracellular Membrane Vesicles Carrying a Single Major Cargo Protein and Analysis of Its Transport Mechanism

Extracellular membrane vesicles (EMVs) play an important role in various bacterial activities. EMVs have potential for use as vaccines, drug-delivery vehicles, platforms for extracellular production of recombinant proteins, and so on. In this study, we newly isolated a cold-adapted bacterium, Shewanella vesiculosa HM13, which abundantly produces EMVs, characterized them, and analyzed their cargo transport mechanism. S. vesiculosa HM13, isolated from the intestine of a horse mackerel as a prospective host for a low-temperature secretory protein expression system, produced a single major secretory protein, P49, of unknown function in the culture supernatant. Analysis using sucrose density gradient ultracentrifugation indicated that P49 is a cargo protein carried by EMVs. S. vesiculosa HM13 displayed extensive blebbing on the surface of the outer membrane, and the size of blebs was comparable to that of EMVs. These blebs are thought to be precursors of the EMVs. Disruption of the P49 gene resulted in only a marginal decrease in the EMV production, indicating that the EMVs are produced even in the absence of the major cargo protein. Whole genome sequencing of S. vesiculosa HM13 revealed that this bacterium has a gene cluster coding for a non-canonical type II protein secretion system (T2SS) homolog in addition to a gene cluster coding for canonical T2SS. The P49 gene was located downstream of the former gene cluster. To examine the role of the putative non-canonical T2SS-like translocon, we disrupted the gene coding for a putative outer membrane channel of the translocon, named GspD2. The gspD2 disruption lead to disappearance of P49 in the EMV fraction, whereas the production of EMVs was not significantly affected by this mutation. These results are indicative that the T2SS-like machinery functions as a novel type of protein translocon responsible for selective cargo loading to the EMVs. We also found that GFP fused to the C-terminus of P49 expressed in S. vesiculosa HM13 was transported to EMVs, indicating that P49 is useful as a carrier to deliver the fusion partner to EMVs. These findings deepen our understanding of the mechanism of biogenesis of EMVs and facilitate their applications.

Development of a regulatable low-temperature protein expression system using the psychrotrophic bacterium, Shewanella livingstonensis Ac10, as the host

A low-temperature protein expression system is useful for the production of thermolabile proteins. We previously developed a system that enables constitutive protein production at low temperatures, using the psychrotrophic bacterium Shewanella livingstonensis Ac10 as the host. To increase the utility of this system, in the present study, we introduced a repressible promoter of the trp operon of this bacterium into the system. When ß-lactamase was produced under the control of this promoter at 18°C and 4°C, the yields were 75 and 33 mg/L-culture, respectively, in the absence of L-Trp, and the yields were decreased by 72% and 77%, respectively, in the presence of L-Trp. We also found that 3-indoleacrylic acid, a competitive inhibitor of the Escherichia coli trp repressor, increased the expression of the reporter gene. This repressible gene expression system would be useful for regulatable recombinant protein production at low temperatures.

Structural Elucidation of a Novel Lipooligosaccharide from the Antarctic Bacterium OMVs Producer Shewanella sp. HM13

Shewanella sp. HM13 is a cold-adapted Gram-negative bacterium isolated from the intestine of a horse mackerel. It produces a large amount of outer membrane vesicles (OMVs), which are particles released in the medium where the bacterium is cultured. This strain biosynthesizes a single major cargo protein in the OMVs, a fact that makes Shewanella sp. HM13 a good candidate for the production of extracellular recombinant proteins. Therefore, the structural characterization of the components of the vesicles, such as lipopolysaccharides, takes on a fundamental role for understanding the mechanism of biogenesis of the OMVs and their applications. The aim of this study was to investigate the structure of the oligosaccharide (OS) isolated from Shewanella sp. HM13 cells as the first step for a comparison with that from the vesicles. The lipooligosaccharide (LOS) was isolated from dry cells, purified, and hydrolyzed by alkaline treatment. The obtained OS was analyzed completely, and the composition of fatty acids was obtained by chemical methods. In particular, the OS was investigated in detail by ¹H and 13C NMR spectroscopy and MALDI-TOF mass spectrometry. The oligosaccharide was characterized by the presence of a residue of 8-amino-3,8-dideoxy-manno-oct-2-ulosonic acid (Kdo8N) and of a d,d-heptose, with both residues being identified in other oligosaccharides from Shewanella species.

Rendezvous Technique Using Double Balloon Endoscope for Removal of Multiple Intrahepatic Bile Duct Stones in Hepaticojejunostomy After Living Donor Liver Transplant: A Case Report

Cholangitis is a major complication following transplantation. We report a living donor liver transplant (LDLT) patient with cholangitis due to multiple stones in the intrahepatic bile duct during hepaticojejunostomy anastomosis, who was successfully treated with the rendezvous technique using double balloon endoscope. A 64-year-old woman underwent LDLT with right lobe graft and hepaticojejunostomy for Wilson disease. There was bile leakage with biliary peritonitis, which was treated conservatively after transplant. Two years after surgery, she developed reiterated cholangitis due to stenosis of hepaticojejunostomy anastomosis and multiple stones in the intrahepatic bile ducts. Percutaneous transhepatic biliary drainage was performed. The size of the drainage tube was increased, and the anastomotic area was dilated in a stepwise manner using a balloon catheter. The stones were crushed and lithotomy was performed using electronic hydraulic lithotripsy through cholangioscopy. Finally, lithotomy was performed for the remaining stones through endoscopic retrograde cholangiography with the rendezvous technique using the double balloon endoscope. Rendezvous approach with percutaneous transhepatic biliary drainage and double balloon endoscopic retrograde cholangiography was an effective treatment for the multiple intrahepatic stones in hepaticojejunostomy following LDLT with right lobe graft.

Purification and characterization of 1-acyl-sn-glycerol-3-phosphate acyltransferase with a substrate preference for polyunsaturated fatty acyl donors from the eicosapentaenoic acid-producing bacterium Shewanella livingstonensis Ac10

1-Acyl-sn-glycerol-3-phosphate acyltransferase (designated as PlsC in bacteria) catalyzes the acylation of lysophosphatidic acid and is responsible for the de novo production of phosphatidic acid, a precursor for the synthesis of various membrane glycerophospholipids. Because PlsC is an integral membrane protein, it is generally difficult to solubilize it without causing its inactivation, which has been hampering its biochemical characterization despite its ubiquitous presence and physiological importance. Most biochemical studies of PlsC have been carried out using crude membrane preparations or intact cells. In this study, we succeeded in solubilization and purification of a recombinant PlsC in its active form from the eicosapentaenoic acid-producing bacterium Shewanella livingstonensis Ac10 using 6-cyclohexyl-1-hexyl-β-d-maltoside as the detergent. We characterized the purified enzyme and found that it has a substrate preference for the acyl donors with a polyunsaturated fatty acyl group, such as eicosapentaenoyl group. These results provide a new method for purification of the PlsC family enzyme and demonstrate the occurrence of a new PlsC with unique substrate specificity.

A novel 1-acyl-sn-glycerol-3-phosphate O-acyltransferase homolog for the synthesis of membrane phospholipids with a branched-chain fatty acyl group in Shewanella livingstonensis Ac10

1-Acyl-sn-glycerol-3-phosphate O-acyltransferase (PlsC) plays an essential role in the formation of phosphatidic acid, a precursor of various membrane phospholipids (PLs), in bacteria by catalyzing the introduction of an acyl group into the sn-2 position of lysophosphatidic acid. Various bacteria produce more than one PlsC. However, the physiological significance of the occurrence of multiple PlsCs is poorly understood. A psychrotrophic bacterium, Shewanella livingstonensis Ac10, which produces eicosapentaenoic acid at low temperatures, has five putative PlsCs (PlsC1-5). We previously showed that PlsC1 is responsible for the production of PLs containing an eicosapentaenoyl group. Here, we characterized another putative PlsC of this bacterium named PlsC4. We generated a plsC4-disrupted mutant and found that PLs containing 13:0 found in the parental strain were almost completely absent in the mutant. The loss of these PLs was suppressed by introduction of a plsC4-expression plasmid. PLs containing 15:0 were also drastically decreased by plsC4 disruption. Gas chromatography-mass spectrometry analysis of fatty acyl methyl esters derived from PLs of the parental strain showed that the 13:0 and 15:0 groups were an 11-methyllauroyl group and a 13-methylmyristoyl group, respectively. Phospholipase A2 treatment revealed that these fatty acyl groups were linked to the sn-2 position of PLs. Thus, PlsC4 is a new type of PlsC homolog that is responsible for the synthesis of PLs containing a branched-chain fatty acyl group at the sn-2 position and plays a clearly different role from that of PlsC1 in vivo.

Dimer-monomer equilibrium of human HSP27 is influenced by the in-cell macromolecular crowding environment and is controlled by fatty acids and heat

Small heat shock protein 27 (HSP27) is an essential element of the proteostasis network in human cells. The HSP27 monomer coexists with the dimer, which can bind unfolded client proteins. Here, we evaluated the in-cell dimer-monomer equilibrium and its relevance to the binding of client proteins in a normal human vascular endothelial cell line. When cells were treated with a membrane-permeable crosslinker, the protein existed primarily as a free monomer (27 kDa) with a markedly smaller percentage of dimer (54 kDa), hetero-conjugates, and minor smear-like bands. When the protein was crosslinked in a cell-free lysate, two of the hetero-conjugates that were crosslinked in live cells were also detected, but the dimer and other complexes were absent. However, when cells were pretreated with fatty acid (FA) and/or heat (42.5 °C), dissociation of the dimer was selectively prevented and two types of covalently linked dimers were increased. These changes occurred most prominently in cells treated with docosahexaenoic acid (DHA) and heat, which appeared to intensify the heat resistance of the cell. Both the formation of covalently linked dimers and heat resistance were prevented by N-acetylcysteine. By contrast, nearly all of the free monomers in the lysate converted to disulfide bond-linked dimers by a simple, long incubation at 4 °C. These results strongly suggest that the monomer-dimer equilibrium of HSP27 was inversed between the in-cell and cell-free systems. Temperature- and amphiphile-regulated dimerization was restricted probably due to the low hydration of the in-cell crowding environment.

Synthesis and Functional Assessment of a Novel Fatty Acid Probe, ω-Ethynyl Eicosapentaenoic Acid Analog, to Analyze the in Vivo Behavior of Eicosapentaenoic Acid

Eicosapentaenoic acid (EPA) is an ω-3 polyunsaturated fatty acid that plays various beneficial roles in organisms from bacteria to humans. Although its beneficial physiological functions are well-recognized, a molecular probe that enables the monitoring of its in vivo behavior without abolishing its native functions has not yet been developed. Here, we designed and synthesized an ω-ethynyl EPA analog (eEPA) as a tool for analyzing the in vivo behavior and function of EPA. eEPA has an ω-ethynyl group tag in place of the ω-methyl group of EPA. An ethynyl group has a characteristic Raman signal and can be visualized by Raman scattering microscopy. Moreover, this group can specifically react in situ with azide compounds, such as those with fluorescent group, via click chemistry. In this study, we first synthesized eEPA efficiently based on the following well-known strategies. To introduce four C-C double bonds, a coupling reaction between terminal acetylene and propargylic halide or tosylate was employed, and then, by simultaneous and stereoselective partial hydrogenation with P-2 nickel, the triple bonds were converted to cis double bonds. One double bond and an ω-terminal C-C triple bond were introduced by Wittig reaction with a phosphonium salt harboring an ethynyl group. Then, we evaluated the in vivo function of the resulting probe by using an EPA-producing bacterium, Shewanella livingstonensis Ac10. This cold-adapted bacterium inducibly produces EPA at low temperatures, and the EPA-deficient mutant (ΔEPA) shows growth retardation and abnormal morphology at low temperatures. When eEPA was exogenously supplemented to ΔEPA, eEPA was incorporated into the membrane phospholipids as an acyl chain, and the amount of eEPA was about 5% of the total fatty acids in the membrane, which is comparable to the amount of EPA in the membrane of the parent strain. Notably, by supplementation with eEPA, the growth retardation and abnormal morphology of ΔEPA were almost completely suppressed. These results indicated that eEPA mimics EPA well and is useful for analyzing the in vivo behavior of EPA.

Development of a versatile method for targeted gene deletion and insertion by using the pyrF gene in the psychrotrophic bacterium, Shewanella livingstonensis Ac10

Shewanella livingstonensis Ac10, a psychrotrophic bacterium isolated from Antarctic seawater, grows well at low temperatures close to 0°C. The bacterium is useful as a host in a low-temperature protein expression system. It is also useful as a model microorganism to investigate the mechanisms of microbial cold-adaptation. Versatile genetic manipulation techniques would be useful to investigate the biology of this bacterium and to develop its applications. In this study, we developed a method for targeted gene deletion and insertion by using the gene coding for orotidine-5'-phosphate decarboxylase (pyrF), which is involved in pyrimidine synthesis. We found that S. livingstonensis Ac10 is sensitive to 5-fluoroorotic acid (5-FOA), which is converted to a highly toxic compound by the product of pyrF. A uracil-auxotrophic strain resistant to 5-FOA was constructed by deleting pyrF, thus allowing the use of a plasmid-borne copy of pyrF for selection of recombinants. We constructed the pyrF complementation suicide plasmid pKKP, which contains pyrF, the R6K replication origin, the mob site of RP4, an antibiotic marker gene, and a multiple cloning site. To demonstrate pyrF-based gene replacement, we deleted the internal region of orf5, the gene coding for an eicosapentaenoic acid (EPA) synthesis enzyme. We also successfully inserted a His₆-tag-coding sequence into orf8, the gene coding for another EPA synthesis enzyme. This system allows the markerless deletion and insertion of desired sequences at specific sites in the genome, which remarkably facilitates genetic manipulation of this bacterium.

Effects of habitual aerobic exercise on the relationship between intramyocellular or extramyocellular lipid content and arterial stiffness

The accumulation of intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) is associated with arterial stiffness in middle-aged and older adults. Habitual aerobic exercise induces the improvement of arterial stiffness with reduction in fat accumulation. However, the relationship between aerobic exercise-induced changes in muscular lipids and arterial stiffness remains unclear. The purpose of this study was to investigate whether habitual aerobic exercise-induced changes in IMCL and EMCL content would lead to an improvement of arterial stiffness. First, in a cross-sectional study, we investigated whether cardiorespiratory fitness level affects the association between IMCL or EMCL content and arterial stiffness in 60 middle-aged and older subjects (61.0±1.3 years). Second, in an intervention study, we examined whether aerobic exercise training-induced changes in IMCL and EMCL content are associated with a reduction in arterial stiffness in 18 middle-aged and older subjects (67.0±1.7 years). In the cross-sectional study, IMCL content was negatively correlated with brachial-ankle pulse wave velocity (baPWV) (r=-0.47, P<0.05), whereas EMCL content was positively correlated with baPWV (r=0.48, P<0.05) in the low-fitness group, but was not correlated in the high-fitness group. Furthermore, 8-week aerobic exercise training in older adults increased IMCL content and reduced EMCL content. The training-induced change in baPWV was negatively correlated with training-induced changes in IMCL but was positively correlated with training-induced changes in EMCL. These findings suggest that aerobic exercise training-induced changes in IMCL and EMCL content may be related to a reduction in arterial stiffness in middle-aged and older adults.

Development and pathological changes of neurovascular unit regulated by hypoxia response in the retina

Retina is a highly vascularized tissue with a high oxygen and metabolic demand receiving light located in the back of the eye. The development and the maintenance of the retinal vasculature are important to regulate the homeostasis in the tissue. α Subunits of hypoxia-inducible factor (HIF) are key molecules in hypoxia response inducing genes required for cell survival such as vascular endothelial growth factor under hypoxia. Neurons, glia, and vascular endothelium cells interdependently form neurovascular unit in the retina tightly regulated by hypoxia response via HIF expression. A corruption of the precise hypoxia response in the developmental or matured retinal tissue may lead congenital vascular anomalies or adult neovascular ocular diseases. To regulate hypoxia response through HIF activity would be an ideal therapeutic target for these vision-threatening eye diseases.

Nar is the dominant dissimilatory nitrate reductase under high pressure conditions in the deep-sea denitrifier Pseudomonas sp. MT-1

In this paper, relative nitrate reductase activities of the soluble and membrane fractions of MT-1 grown anaerobically under atmospheric pressure in the presence of 30 mM NaNO3 were measured. In the analyses, the diazocoupling method was employed to determine the concentration of nitrite formed. Follow-up recent experiments have revealed that formed coupling compound lose its color rapidly, but this instability is unusual. The authors recognized the possibility that they failed to quantify the accurate concentration of nitrite formed and agree the additional in-depth analyses should be performed. Thus, the JGAM editorial board agreed to retract the paper.

Nar is the dominant dissimilatory nitrate reductase under high pressure conditions in the deep-sea denitrifier Pseudomonas sp. MT-1

The deep-sea denitrifier Pseudomonas sp. MT-1 has two gene clusters encoding dissimilatory nitrate reductases, periplasmic nitrate reductase (Nap) and membrane-bound nitrate reductase (Nar). In order to investigate the physiological role of these enzymes, we constructed the disrupted mutants of napA, narG, and narK (encoding the catalytic subunits of Nap and Nar, as well as the nitrate transporter, respectively). The napA mutant showed almost the same growth rate as the wild-type under both atmospheric and high pressure of 30 MPa. On the other hand, the narG and narK mutants showed growth deficiencies under atmospheric pressure which were more pronounced at a pressure of 30 MPa. Thus, Nar was shown to be the dominant dissimilatory nitrate reductase in MT-1, especially under high pressure, whereas Nap can support the growth with denitrification to some extent. Further, nitrate reductase activity of the soluble and membrane fractions of MT-1 was measured under high pressure. Both activities were highly piezotolerant even under a pressure of 150 MPa. Therefore, the stability of nitrate reductases under high pressure is not a limiting step for the growth of MT-1 under these conditions. Although the reason why Nar rather than Nap is dominant and the physiological role of Nap in MT-1 are still unclear, we have demonstrated the mechanisms of the denitrification system in the environment of the deep-sea.

Alkyl hydroperoxide reductase enhances the growth of Leuconostoc mesenteroides lactic acid bacteria at low temperatures

Lactic acid bacteria (LAB) can cause deterioration of food quality even at low temperatures. In this study, we investigated the cold-adaptation mechanism of a novel food spoilage LAB, Leuconostoc mesenteroides NH04 (NH04). L. mesenteroides was isolated from several spoiled cooked meat products at a high frequency in our factories. NH04 grew rapidly at low temperatures within the shelf-life period and resulted in heavy financial losses. NH04 grew more rapidly than related strains such as Leuconostoc mesenteroides NBRC3832 (NBRC3832) at 10°C. Proteome analysis of NH04 demonstrated that this strain produces a homolog of alkyl hydroperoxide reductase––AhpC––the expression of which can be induced at low temperatures. The expression level of AhpC in NH04 was approximately 6-fold higher than that in NBRC3832, which was grown under the same conditions. Although AhpC is known to have an anti-oxidative role in various bacteria by catalyzing the reduction of alkyl hydroperoxide and hydrogen peroxide, the involvement of AhpC in cold adaptation of food spoilage bacteria was unclear. We introduced an expression plasmid containing ahpC into NBRC3832, which grows slower than NH04 at 10°C, and found that expression of AhpC enhanced growth. These results demonstrated that AhpC, which likely increases anti-oxidative capacity of LAB, plays an important role in their rapid growth at low temperatures.

Correlation between portal vein anatomy and bile duct variation in 407 living liver donors

Our aim was to determine whether variant bile duct (BD) anatomy is associated with portal vein (PV) and/or hepatic artery (HA) anatomy. We examined the associations between BD anatomy and PV and/or HA anatomy in 407 living donor transplantation donors. We also examined whether the right posterior BD (RPBD) course was associated with the PV and/or HA anatomy. Variant PV, HA and BD anatomies were found in 11%, 25% and 25%, respectively, of 407 donors enrolled in this study. The presence of a variant BD was more frequently associated with a variant PV than with a normal PV (61% vs. 20%, p < 0.0001). By contrast, the presence of a variant HA was not associated with a variant BD. A supraportal RPBD was found in 357 donors (88%) and an infraportal RPBD was found in 50 donors (12%). An infraportal RPBD was significantly more common in donors with a variant PV than in donors with a normal PV (30% vs. 10%, p = 0.0004). Variant PV, but not variant HA, anatomies were frequently associated with variant BD anatomy. Additionally, an infraportal RPBD was more common in donors with a variant PV than in donors with a normal PV.

[Chemical approach to analyze the physiological function of phospholipids with polyunsaturated fatty acyl chain]

Polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) occur in biological membranes as acyl groups of phospholipids and exhibit remarkable physiological activities. In human, they have various beneficial effects on health such as protective effects against cardiovascular disease, inflammation, and cancer. We have been studying their physiological functions in bacteria, which have a much simpler membrane structure than eukaryotes. We found that the cell division of a marine bacterium, Shewanella livingstonensis Ac10, is inhibited and shows growth retardation by disruption of its EPA biosynthesis genes. We synthesized a fluorescent analog of EPA-containing phospholipids (EPA-PLs) as a chemical probe to analyze their subcellular distribution and found that it is localized at the center of the cell undergoing cell division. This localization was shown to depend on the structure of the hydrocarbon chain of the phospholipids. We also examined the effects of EPA-PLs on the folding of Omp74, a major membrane protein of this bacterium, by using liposomes and found that EPA-PLs facilitated the folding process. The results imply that EPA-PLs function as a chemical chaperone in the folding of membrane proteins. These findings would contribute to understanding of the physiological function of phospholipids with polyunsaturated fatty acyl chains in various biological membranes.

Glutathione contributes to the efflux of selenium from hepatoma cells

Selenite is a selenium source for selenoprotein biosynthesis in mammalian cells. Although previous studies have suggested the involvement of glutathione (GSH) and/or thioredoxin reductase in selenite metabolism, intracellular selenite metabolism remains largely unknown. Here, we report that GSH depletion did not affect the amount of selenoprotein in Hepa 1-6 cells, suggesting that GSH does not play a central role in the reduction of selenite in selenoprotein biosynthesis. On the other hand, we found that GSH is involved in the efflux of low-molecular-weight selenium compounds from cells, presumably via the formation of selenodiglutathione. Moreover, selenite inhibited the efflux of a fluorescent bimane-GS conjugate that is mediated by ATP-dependent multidrug-resistant proteins, implying the existence of an active transporter for selenodiglutathione. This is the first report demonstrating that GSH plays a role in selenium excretion from cells by forming a GSH-conjugate, which may contribute to the distribution, detoxification, and homeostasis of selenium in the body.