Prevalence of Selected Polymorphisms of Il7R, CD226, CAPSL, and CLEC16A Genes in Children and Adolescents with Autoimmune Thyroid Diseases

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are common autoimmune endocrine disorders in children. Studies indicate that apart from environmental factors, genetic background significantly contributes to the development of these diseases. This study aimed to assess the prevalence of selected single-nucleotide polymorphisms (SNPs) of Il7R, CD226, CAPSL, and CLEC16A genes in children with autoimmune thyroid diseases. We analyzed SNPs at the locus rs3194051, rs6897932 of IL7R, rs763361 of CD226, rs1010601 of CAPSL, and rs725613 of CLEC16A gene in 56 HT patients, 124 GD patients, and 156 healthy children. We observed significant differences in alleles IL7R (rs6897932) between HT males and the control group (C > T, p = 0.028) and between all GD patients and healthy children (C > T, p = 0.035) as well as GD females and controls (C > T, p = 0.018). Moreover, the C/T genotype was less frequent in GD patients at rs6897932 locus and in HT males at rs1010601 locus. The presence of the T allele in the IL7R (rs6897932) locus appears to have a protective effect against HT in males and GD in all children. Similarly, the presence of the T allele in the CAPSL locus (rs1010601) seems to reduce the risk of HT development in all patients.

The exoprotein Gbp of Fusobacterium nucleatum promotes THP-1 cell lipid deposition by binding to CypA and activating PI3K-AKT/MAPK/NF-κB pathways

INTRODUCTION

Growing evidence has shown the correlation between periodontitis and atherosclerosis, while our knowledge on the pathogenesis of periodontitis-promoting atherosclerosis is far from sufficient.

OBJECTIVES

Illuminate the pathogenic effects of Fusobacterium nucleatum (F. nucleatum) on intracellular lipid deposition in THP-1-derived macrophages and elucidate the underlying pathogenic mechanism of how F. nucleatum promoting atherosclerosis.

METHODS AND RESULTS

F. nucleatum was frequently detected in different kinds of atherosclerotic plaques and its abundance was positively correlated with the proportion of macrophages. In vitro assays showed F. nucleatum could adhere to and invade THP-1 cells, and survive continuously in macrophages for 24 h. F. nucleatum stimulation alone could significantly promote cellular inflammation, lipid uptake and inhibit lipid outflow. The dynamic gene expression of THP-1 cells demonstrated that F. nucleatum could time-serially induce the over-expression of multiple inflammatory related genes and activate NF-κB, MAPK and PI3K-AKT signaling pathways. The exoprotein of F. nucleatum, D-galactose-binding protein (Gbp), acted as one of the main pathogenic proteins to interact with the Cyclophilin A (CypA) of THP-1 cells and induced the activation of the NF- κB, MAPK and PI3K-AKT signaling pathways. Furthermore, use of six candidate drugs targeting to the key proteins in NF- κB, MAPK and PI3K-AKT pathways could dramatically decrease F. nucleatum induced inflammation and lipid deposition in THP-1 cells.

CONCLUSIONS

This study suggests that the periodontal pathogen F. nucleatum can activate macrophage PI3K-AKT/MAPK/NF-κB signal pathways, promotes inflammation, enhances cholesterol uptake, reduces lipid excretion, and promotes lipid deposition, which may be one of its main strategies promoting the development of atherosclerosis.

Treatment recommendations for glycogen storage disease type IB- associated neutropenia and neutrophil dysfunction with empagliflozin: Consensus from an international workshop

Glycogen storage disease type Ib (GSD Ib, biallelic variants in SLC37A4) is a rare disorder of glycogen metabolism complicated by neutropenia/neutrophil dysfunction. Since 2019, the SGLT2-inhibitor empagliflozin has provided a mechanism-based treatment option for the symptoms caused by neutropenia/neutrophil dysfunction (e.g. mucosal lesions, inflammatory bowel disease). Because of the rarity of GSD Ib, the published evidence on safety and efficacy of empagliflozin is still limited and does not allow to develop evidence-based guidelines. Here, an international group of experts provides 14 best practice consensus treatment recommendations based on expert practice and review of the published evidence. We recommend to start empagliflozin in all GSD Ib individuals with clinical or laboratory signs related to neutropenia/neutrophil dysfunction with a dose of 0.3-0.4 mg/kg/d given as a single dose in the morning. Treatment can be started in an outpatient setting. The dose should be adapted to the weight and in case of inadequate clinical treatment response or side effects. We strongly recommend to pause empagliflozin immediately in case of threatening dehydration and before planned longer surgeries. Discontinuation of G-CSF therapy should be attempted in all individuals. If available, 1,5-AG should be monitored. Individuals who have previously not tolerated starches should be encouraged to make a new attempt to introduce starch in their diet after initiation of empagliflozin treatment. We advise to monitor certain safety and efficacy parameters and recommend continuous, alternatively frequent glucose measurements during the introduction of empagliflozin. We provide specific recommendations for special circumstances like pregnancy and liver transplantation.

The metabolic basis of inherited neutropenias

Neutrophils are the shortest-lived blood cells, which requires a prodigious degree of proliferation and differentiation to sustain physiologically sufficient numbers and be poised to respond quickly to infectious emergencies. More than 107 neutrophils are produced every minute in an adult bone marrow-a process that is tightly regulated by a small group of cytokines and chemical mediators and dependent on nutrients and energy. Like granulocyte colony-stimulating factor, the primary growth factor for granulopoiesis, they stimulate signalling pathways, some affecting metabolism. Nutrient or energy deficiency stresses the survival, proliferation, and differentiation of neutrophils and their precursors. Thus, it is not surprising that monogenic disorders related to metabolism exist that result in neutropenia. Among these are pathogenic mutations in HAX1, G6PC3, SLC37A4, TAFAZZIN, SBDS, EFL1 and the mitochondrial disorders. These mutations perturb carbohydrate, lipid and/or protein metabolism. We hypothesize that metabolic disturbances may drive the pathogenesis of a subset of inherited neutropenias just as defects in DNA damage response do in Fanconi anaemia, telomere maintenance in dyskeratosis congenita and ribosome formation in Diamond-Blackfan anaemia. Greater understanding of metabolic pathways in granulopoiesis will identify points of vulnerability in production and may point to new strategies for the treatment of neutropenias.

[Durable remission of T-cell prolymphocytic leukemia with CLEC16A::IL2 after allogeneic hematopoietic stem cell transplantation]

A 64-year-old woman presented with fine motor impairment in both hands. MRI revealed a contrast-enhanced lesion in the medulla oblongata. Lymphoid cells with abnormal blebs were observed and a CD4+/CD8+ double positive (DP) T cell population was detected by flow cytometry (FCM) in the bone marrow (BM) and the peripheral blood (PB). CLEC16A::IL2 fusion gene was identified by whole exome sequencing with DNA prepared from DP T cells. Clonal rearrangement of the T-cell receptor gene and expression of TCL1A protein were detected. This led to a diagnosis of T-cell prolymphocytic leukemia (T-PLL) with central nervous system (CNS) infiltration. Abnormal cells in BM and PB became undetectable on microscopy and FCM, and the CNS lesion disappeared on MRI after second-line therapy with alemtuzumab. Meanwhile, the CLEC16A::IL2 fusion mRNA remained detectable in PB. Allogeneic hematopoietic stem-cell transplantation was performed, and the fusion mRNA has now been undetectable for more than 5 years since transplantation. This is the first report of a T-PLL case with a CLEC16A::IL2 fusion gene.

DBS are suitable for 1,5-anhydroglucitol monitoring in GSD1b and G6PC3-deficient patients taking SGLT2 inhibitors to treat neutropenia

Glycogen storage disease type Ib (GSD1b) and G6PC3-deficiency are rare autosomal recessive diseases caused by inactivating mutations in SLC37A4 (coding for G6PT) and G6PC3, respectively. Both diseases are characterized by neutropenia and neutrophil dysfunction due to the intracellular accumulation of 1,5-anhydroglucitol-6-phosphate (1,5-AG6P), a potent inhibitor of hexokinases. We recently showed that the use of SGLT2 inhibitor therapy to reduce tubular reabsorption of its precursor, 1,5-anhydroglucitol (1,5-AG), a glucose analog present in blood, successfully restored the neutropenia and neutrophil function in G6PC3-deficient and GSD1b patients. The intra-individual variability of response to the treatment and the need to adjust the dose during treatment, especially in pediatric populations, can only be efficiently optimized if the concentration of 1,5-AG in blood is monitored during treatment, together with the patients' clinical signs and symptoms. Monitoring the 1,5-AG levels would be greatly simplified if it could be performed on dry blood spots (DBS) which are easy to collect, store and transport. The challenge is to know if a suitable method can be developed to perform accurate and reproducible assays for 1,5-AG using DBS. Here, we describe and validate an assay that quantifies 1,5-AG in DBS using isotopic dilution quantitation by LC-MS/MS that should greatly facilitate patients' follow-up. 1,5-AG levels measured in plasma and DBS give comparable values. This assay was used to monitor the levels of 1,5-AG in DBS from 3 G6PC3-deficient and 6 GSD1b patients during treatment with SGLT2 inhibitors. We recommend this approach to verify the adequate therapeutical response and compliance to the treatment in G6PC3-deficient and GSD1b patients treated with SGLT2 inhibitors.

Perspectives of Rare Disease Experts on Newborn Genome Sequencing

Importance

Newborn genome sequencing (NBSeq) can detect infants at risk for treatable disorders currently undetected by conventional newborn screening. Despite broad stakeholder support for NBSeq, the perspectives of rare disease experts regarding which diseases should be screened have not been ascertained.

Objective

To query rare disease experts about their perspectives on NBSeq and which gene-disease pairs they consider appropriate to evaluate in apparently healthy newborns.

Design, Setting, and Participants

This survey study, designed between November 2, 2021, and February 11, 2022, assessed experts' perspectives on 6 statements related to NBSeq. Experts were also asked to indicate whether they would recommend including each of 649 gene-disease pairs associated with potentially treatable conditions in NBSeq. The survey was administered between February 11 and September 23, 2022, to 386 experts, including all 144 directors of accredited medical and laboratory genetics training programs in the US.

Exposures

Expert perspectives on newborn screening using genome sequencing.

Main Outcomes and Measures

The proportion of experts indicating agreement or disagreement with each survey statement and those who selected inclusion of each gene-disease pair were tabulated. Exploratory analyses of responses by gender and age were conducted using t and χ2 tests.

Results

Of 386 experts invited, 238 (61.7%) responded (mean [SD] age, 52.6 [12.8] years [range 27-93 years]; 126 [52.9%] women and 112 [47.1%] men). Among the experts who responded, 161 (87.9%) agreed that NBSeq for monogenic treatable disorders should be made available to all newborns; 107 (58.5%) agreed that NBSeq should include genes associated with treatable disorders, even if those conditions were low penetrance; 68 (37.2%) agreed that actionable adult-onset conditions should be sequenced in newborns to facilitate cascade testing in parents, and 51 (27.9%) agreed that NBSeq should include screening for conditions with no established therapies or management guidelines. The following 25 genes were recommended by 85% or more of the experts: OTC, G6PC, SLC37A4, CYP11B1, ARSB, F8, F9, SLC2A1, CYP17A1, RB1, IDS, GUSB, DMD, GLUD1, CYP11A1, GALNS, CPS1, PLPBP, ALDH7A1, SLC26A3, SLC25A15, SMPD1, GATM, SLC7A7, and NAGS. Including these, 42 gene-disease pairs were endorsed by at least 80% of experts, and 432 genes were endorsed by at least 50% of experts.

Conclusions and Relevance

In this survey study, rare disease experts broadly supported NBSeq for treatable conditions and demonstrated substantial concordance regarding the inclusion of a specific subset of genes in NBSeq.

Impaired autophagy promotes hair loss in the C3H/HeJ mouse model of alopecia areata

Alopecia areata (AA) involves an aberrant immune attack on the hair follicle (HF), which leads to hair loss. Previous genetic data from our lab pointed to a connection between macroautophagy/autophagy and AA pathogenesis, and GWAS identified STX17, CLEC16A and BCL2L11/BIM as risk factors for AA. Additionally, AA patients have copy number deletions in region spanning the ATG4B gene. To test whether autophagy might contribute to disease pathogenesis in AA, we investigated autophagic activity in C3H/HeJ mouse model. We found that autophagy protein SQSTM1 accumulated in HF of AA mice, while in immune cells from AA skin-draining lymph nodes SQSTM1 was not altered, suggesting that autophagic activity is inhibited in the HF of AA mice. Induction of autophagy with Tat-BECN1 peptide attenuated AA, while treatment with the autophagy blocker chloroquine promoted disease, compared to untreated AA mice. Together, our findings suggest the involvement of impaired autophagy in disease pathogenesis of AA.Abbreviations: AA: alopecia areata; CQ: chloroquine; GWAS: genome-wide association studies; HF: hair follicle; MHC: major histocompatibility complex; SDLN: skin-draining lymph nodes.

Understanding the role of SGLT2 inhibitors in glycogen storage disease type Ib: the experience of one UK centre

BACKGROUND

Glycogen storage disease type Ib (GSD Ib) is a severe disorder of carbohydrate metabolism due to bi-allelic variants in SLC37A4. It is associated with neutropaenia and neutrophil dysfunction, which has recently been attributed to the accumulation of 1,5-anhydroglucitol-6-phosphate (1,5AG6P) within neutrophils. Treatment with sodium-glucose co-transporter-2 (SGLT2) inhibitors, such as empagliflozin, is a novel therapy that reduces 1,5-anhydroglucitol (1,5AG) in plasma.

RESULTS

We report our experience in treating 8 paediatric GSD Ib patients with empagliflozin with a cumulative treatment time greater than 12 years. Treatment with a median dose of 5 mg (0.22 mg/kg height weight) of empagliflozin resulted in improvement in bowel health, growth, and laboratory parameters. Plasma 1,5AG levels reduced by a median of 78%. Baseline 1,5AG levels in our cohort were higher than in adult patients with GSD Ib. Hypoglycaemia on empagliflozin treatment occurred in 50% of our cohort.

CONCLUSION

We report the largest single centre cohort of GSD Ib patients treated with empagliflozin to date. Treatment with SGLT2 inhibitors is a novel and favourable treatment option for neutropaenia and neutrophil dysfunction in GSD Ib. We suggest a low starting dose of empagliflozin with careful titration due to the risk of hypoglycaemia. The interpretation of 1,5AG levels and their role in treatment monitoring is yet to be established, and requires ongoing research.

ECHS1, an interacting protein of LASP1, induces sphingolipid-metabolism imbalance to promote colorectal cancer progression by regulating ceramide glycosylation

Sphingolipid metabolic dysregulation has increasingly been considered to be a drug-resistance mechanism for a variety of tumors. In this study, through an LC-MS assay, LIM and SH3 protein 1 (LASP1) was identified as a sphingolipid-metabolism-involved protein, and short-chain enoyl-CoA hydratase (ECHS1) was identified as a new LASP1-interacting protein through a protein assay in colorectal cancer (CRC). Gain- and loss-of-function analyses demonstrated the stimulatory role played by ECHS1 in CRC cell proliferation, migration, and invasion in vitro and in vivo. Mechanistic studies of the underlying tumor-supportive oncometabolism indicate that ECHS1 enables altering ceramide (Cer) metabolism that increases glycosphingolipid synthesis (HexCer) by promoting UDP-glucose ceramide glycosyltransferase (UGCG). Further analysis showed that ECHS1 promotes CRC progression and drug resistance by releasing reactive oxygen species (ROS) and interfering mitochondrial membrane potential via the PI3K/Akt/mTOR-dependent signaling pathway. Meanwhile, the phenomenon of promoting the survival and drug resistance of CRC cells caused by ECHS1 could be reversed by Eliglustat, a specific inhibitor of UCCG, in vitro and in vivo. IHC assay showed that ECHS1 was overexpressed in CRC tissues, which was related to the differentiation and poor prognosis of CRC patients. This study provides new insight into the mechanism by which phospholipids promote drug resistance in CRC and identifies potential targets for future therapies.

Microtubules in insulin action: what's on the tube?

Microtubules (MT) have a role in the intracellular response to insulin stimulation and subsequent glucose transport by glucose transporter 4 (GLUT4), which resides in specialized storage vesicles that travel through the cell. Before GLUT4 is inserted into the plasma membrane for glucose transport, it undergoes complex trafficking through the cell via the integration of cytoskeletal networks. In this review, we highlight the importance of MT elements in insulin action in adipocytes through a summary of MT depolymerization studies, MT-based GLUT4 movement, molecular motor proteins involved in GLUT4 trafficking, as well as MT-related phenomena in response to insulin and links between insulin action and MT-associated proteins.

A modified fluorescent sensor for reporting glucose concentration in the airway lumen

We have modified the periplasmic Escherichia coli glucose/galactose binding protein (GBP) and labelled with environmentally sensitive fluorophores to further explore its potential as a sensor for the evaluation of glucose concentration in airway surface liquid (ASL). We identified E149C/A213R GBP labelled with N,N’-Dimethyl-N-(iodoacetyl)-N’-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)ethylenediamine (IANBD, emission wavelength maximum 536nm) with a K_d for D-glucose of 1.02mM and a fluorescence dynamic range of 5.8. This sensor was specific for D-glucose and exhibited fluorescence stability in experiments for several hours. The use of E149C/A213R GBP-IANBD in the ASL of airway cells grown at air-liquid-interface (ALI) detected an increase in glucose concentration 10 minutes after raising basolateral glucose from 5 to 15mM. This sensor also reported a greater change in ASL glucose concentration in response to increased basolateral glucose in H441 airway cells compared to human bronchial epithelial cells (HBEC) and there was less variability with HBEC data than that of H441 indicating that HBEC more effectively regulate glucose movement into the ASL. The sensor detected glucose in bronchoalveolar lavage fluid (BALf) from diabetic db/db mice but not normoglycaemic wildtype mice, indicating limited sensitivity of the sensor at glucose concentrations <50μM. Using nasal inhalation of the sensor and spectral unmixing to generate images, E149C/A213R GBP-IANBD fluorescence was detected in luminal regions of cryosections of the murine distal lung that was greater in db/db than wildtype mice. In conclusion, this sensor provides a useful tool for further development to measure luminal glucose concentration in models of lung/airway to explore how this may change in disease.

[Construction and optimization of p-coumaric acid-producing Saccharomyces cerevisiae]

p-Coumaric acid is an important precursor of various natural compounds, such as flavonoids and stilbenes. It has been widely used in biomedicine, food, nutrition and health care industries. Compared with traditional plant extracts and chemical synthesis, microbial synthesis of natural compounds such as p-coumaric acid has attracted wide attention due to its short production cycle and high conversion efficiency. Here a p-coumaric acid-producing Saccharomyces cerevisiae platform strain was developed. First, the tyrosine synthesis competition pathway genes ARO10 and PDC5 were knocked out, and ARO4(K229L) and ARO7(G141S) were mutated to release negative feedback inhibition from tyrosine. The tyrosine ammonia-lyase coding gene TAL from Flavobacterium johnsoniaeu was then integrated into genome and obtained C001 with yield of p-coumaric acid 296.73 mg/L. To further increase the accumulation of p-coumaric acid precursors, 8 genes encoding amino acids and carbohydrate transporters were knocked out and the gluconeogenesis pathway was enhanced. The results showed that GAL2 knockout and overexpression of EcppsA increased the yield of p-coumaric acid to 475.11 mg/L. Finally, the effect of FjTAL anchoring to yeast vacuoles on product accumulation was analyzed, and the highest titer of p-coumaric acid of 593.04 mg/L was obtained after intracellular vacuolar localization of FjTAL. It provided an efficient p-coumaric acid-producing platform strain for the subsequent synthesis of flavonoids and stilbene compounds by enhancing the supply of precursors, blocking the competitive bypass pathway, and using the strategy of subcellular localization.

Genome-wide Characterization and Expression Analysis of Sugar Transporter Family Genes in Woodland Strawberry

In higher plants, sugars are nutrients and important signal molecules. Sugar transporters (STs) facilitate sugar transport across membranes and are associated with loading and unloading of the conducting complex. Strawberry ( Duchesne ex Rozier) is one of the most economically important and widely cultivated fruit crop and a model plant among fleshy fruits worldwide. In this study, 66 woodland strawberry ( L.) ST (FvST) genes were identified and further classified into eight distinct subfamilies in the woodland strawberry genome based on the phylogenetic analysis. In the promoter sequences of FvST gene families, a search for -regulatory elements suggested that some of them might probably be regulated by plant hormones (e.g., salicylic acid, abscisic acid, and auxin), abiotic (e.g., drought, excessive cold, and light), and biotic stress factors. Exon-intron analysis showed that each subfamily manifested closely associated gene architectural features based on similar number or length of exons. Moreover, to comprehend the potential evolution mechanism of FvST gene family, the analysis of genome duplication events was performed. The segmental and tandem duplication analysis elucidated that some of ST genes arose through whole-genome duplication (WGD) or segmental duplication, accompanied by tandem duplications. The expression analysis of 24 FvST genes in vegetative and during fruit development has shown that the expression of several ST genes was tissue and developmental stage specific. Generally, our findings are important in understanding of the allocation of photo assimilates from source to sink cell and provide insights into the genomic organization and expression profiling of FvST gene families in woodland strawberry.

Sfp1 and Rtg3 reciprocally modulate carbon source-conditional stress adaptation in the pathogenic yeast Candida albicans

The pathogenicity of the clinically important yeast, Candida albicans, is dependent on robust responses to host-imposed stresses. These stress responses have generally been dissected in vitro at 30°C on artificial growth media that do not mimic host niches. Yet host inputs, such as changes in carbon source or temperature, are known to affect C. albicans stress adaptation. Therefore, we performed screens to identify novel regulators that promote stress resistance during growth on a physiologically relevant carboxylic acid and at elevated temperatures. These screens revealed that, under these 'non-standard' growth conditions, numerous uncharacterised regulators are required for stress resistance in addition to the classical Hog1, Cap1 and Cta4 stress pathways. In particular, two transcription factors (Sfp1 and Rtg3) promote stress resistance in a reciprocal, carbon source-conditional manner. SFP1 is induced in stressed glucose-grown cells, whereas RTG3 is upregulated in stressed lactate-grown cells. Rtg3 and Sfp1 regulate the expression of key stress genes such as CTA4, CAP1 and HOG1 in a carbon source-dependent manner. These mechanisms underlie the stress sensitivity of C. albicans sfp1 cells during growth on glucose, and rtg3 cells on lactate. The data suggest that C. albicans exploits environmentally contingent regulatory mechanisms to retain stress resistance during host colonisation.

[Genome-wide screening of predicted sugar transporters in Neurospora crassa and the application in hexose fermentation by Saccharomyces cerevisiae]

The lignocellulolytic filamentous fungus Neurospora crassa is able to assimilate various mono- and oligo-saccharides. However, more than half of predicted sugar transporters in the genome are still waiting for functional elucidation. In this study, system analysis of substrate spectra of predicted sugar transporters in N. crassa was performed at genome-wide level. NCU01868 and NCU08152 have the capability of uptaking various hexose, which are named as NcHXT-1 and NcHXT-2 respectively. Their transport activities for glucose were further confirmed by fluorescence resonance energy transfer analysis. Over-expression of either NcHXT-1 or NcHXT-2 in the null-hexose-transporter yeast EBY.VW4000 restored the growth and ethanol fermentation under submerged fermentation with glucose, galactose, or mannose as the sole carbon source. NcHXT-1/-2 homologues were found in a variety of cellulolytic fungi. Functional identification of two filamentous fungal-conserved hexose transporters NcHXT-1/-2 via genome scanning would represent novel targets for ongoing efforts in engineering cellulolytic fungi and hexose fermentation in yeast.

Concurrent TMPRSS2-ERG and SLC45A3-ERG rearrangements plus PTEN loss are not found in low grade prostate cancer and define an aggressive tumor subset

BACKGROUND

SLC45A3 is the second most common ERG partner in prostate cancer (PrCa). Coexisting TMPRSS2 and SLC45A3 rearrangements are found in a subset of cases, but the meaning is still unknown.

METHODS

SLC45A3-ERG and TMPRSS2-ERG rearrangements and their association with ERG and PTEN expression and with clinical and pathological features have been analyzed in 80 PrCa (PSMAR-Biobank, Barcelona, Spain). ERG and PTEN mRNA were assessed by qRT-PCR; TMPRSS2-ERG and SLC45A3-ERG by RT-PCR, FISH, and direct sequencing; and ERG expression by IHC. The endpoints were Gleason score (GS), stage, and PSA progression-free survival.

RESULTS

Single TMPRSS2-ERG was found in 51.6% GS ≤ 7 and 22.2% GS ≥ 8 tumors (P = 0.027). SLC45A3-ERG was found in 25 cases, 20 of them with concurrent TMPRSS2-ERG rearrangement: 11.5% GS = 6, 22.2% GS = 7, and 50% GS ≥ 8 tumors (P = 0.013). Double rearrangements were associated with higher levels of ERG mRNA (P = 0.04). Double rearrangement plus PTEN loss was detected in 0% GS = 6; 14.7% GS = 7, and 29.4% GS ≥ 8 tumors (P = 0.032). Furthermore, this triple change was present in 19.2% stage T3-4 but not in any of stage T2 tumors (P = 0.05). No relationship was found with PSA progression-free survival.

CONCLUSIONS

Single TMPRSS2-ERG translocation is associated with low grade PrCa. Subsequent development of SLC45A3-ERG results in higher ERG expression. The combination of double rearrangement plus PTEN loss, according to our series, is never found in low grade, low stage tumors. These findings could be potentially useful in therapeutic decision making in PrCa. Tumors with combined TMPRSS2-ERG/SLC45A3-ERG fusions plus PTEN loss should be excluded from watchful waiting and are candidates for intensive therapy. Prostate 76:854-865, 2016. © 2016 Wiley Periodicals, Inc.

Role of CTCF in Regulating SLC45A3-ELK4 Chimeric RNA

The chimeric RNA, SLC45A3-ELK4, was found to be a product of cis-splicing between the two adjacent genes (cis-SAGe). Despite the biological and clinical significance of SLC45A3-ELK4, its generating mechanism has not been elucidated. It was shown in one cell line that the binding of transcription factor CTCF to the insulators located at or near the gene boundaries, inversely correlates with the level of the chimera. To investigate the mechanism of such cis-SAGe events, we sequenced potential regions that may play a role in such transcriptional read-through. We could not detect mutations at the transcription termination site, insulator sites, splicing sites, or within CTCF itself in LNCaP cells, thus suggesting a “soft-wired” mechanism in regulating the cis-SAGe event. To investigate the role CTCF plays in regulating the chimeric RNA expression, we compared the levels of CTCF binding to the insulators in different cell lines, as well as clinical samples. Surprisingly, we did not find an inverse correlation between CTCF level, or its bindings to the insulators and SLC45A3-ELK4 expression among different samples. However, in three prostate cancer cell lines, different environmental factors can cause the expression levels of the chimeric RNA to change, and these changes do inversely correlate with CTCF level, and/or its bindings to the insulators. We thus conclude that CTCF and its bindings to the insulators are not the primary reasons for differential SLC45A3-ELK4 expression in different cell lines, or clinical cases. However, they are the likely mechanism for the same cells to respond to different environmental cues, in order to regulate the expression of SLC45A3-ELK4 chimeric RNA. This response to different environmental cues is not general to other cis-SAGe events, as we only found one out of 16 newly identified chimeric RNAs showing a pattern similar to SLC45A3-ELK4.

Genetic variants at 1q32.1, 10q11.2 and 19q13.41 are associated with prostate-specific antigen for prostate cancer screening in two Korean population-based cohort studies

Prostate-specific antigen (PSA) levels are affected by non-cancerous conditions such as benign prostatic hyperplasia, inflammations, and inherited factors. To search for genetic variants associated with PSA levels, we conducted a genome-wide association study (GWAS) using a two-stage design. A total of 554 men from the Korean Cancer Prevention Study-II were used as a discovery stage and 1575 men collected by the Korean Genome Epidemiology Study were used as a replication stage. Analysis by Genome-wide Human single-nucleotide polymorphism (SNP) array 5.0 was performed by using DNAs derived from venous blood. We analyzed the association between genetic variants and PSA levels using multivariate linear regression models, including age as a covariate. We detected 12 genome-wide significant signals on chromosome 1q32.1, 10q11.2, and 19q13.41 between PSA levels and SNPs. The top SNP associated with log PSA levels was rs2153904 in SLC45A3 (p values, 5.24×10(-9) to 2.00×10(-6)). We also investigated GWAS using 754 subjects from KCPS-II cohort whether our genome-wide significant loci were associated with a risk of prostate cancer (PCa) (200 PCa cases and 554 controls). Three of the SNPs on 10q11.2, rs7077830, rs2611489, and rs4631830, were associated with a risk of PCa. However, two loci, 1q32.1 and 19q13, were not significantly associated with a PCa risk. We suggest that our results for some but not all PCa risk SNPs to be associated with PSA levels could be used as an evidence for the advance of individual PCa screening strategies, such as applying a personalized cutoff value for PSA.

[Research on glucose measuring technique by surface plasmon resonance based on thiol coupling]

In the glucose measuring technique by surface plasmon resonance, D-galactose/D-glucose binding protein (GGBP) that can specifically adsorb glucose was introduced, and high-precision specific detection of glucose concentration was realized. In the present paper, the GGBP protein was bound on the surface of SPR sensor through thiol coupling method. GGBP binding experiment was carried out on SPR sensor and then glucose concentration experiment was conducted with this sensor. The results indicated that the SPR sensor had good linearity, stability and repeatability in the range of 0.1-10 mg x dL(-1). SPR sensor bound with GGBP would have great potential and vast development prospects.

Fluorescence intensity- and lifetime-based glucose sensing using glucose/galactose-binding protein

We review progress in our laboratories toward developing in vivo glucose sensors for diabetes that are based on fluorescence labeling of glucose/galactose-binding protein. Measurement strategies have included both monitoring glucose-induced changes in fluorescence resonance energy transfer and labeling with the environmentally sensitive fluorophore, badan. Measuring fluorescence lifetime rather than intensity has particular potential advantages for in vivo sensing. A prototype fiber-optic-based glucose sensor using this technology is being tested.

Exploring the world of phospholipids and their interactions with proteins: the work of William Dowhan

The Gene Encoding the Phosphatidylinositol Transfer Protein Is Essential for Cell Growth (Aitken, J. F., van Heusden, G. P., Temkin, M., and Dowhan, W. (1990) J. Biol. Chem. 265, 4711–4717)

A Phospholipid Acts as a Chaperone in Assembly of a Membrane Transport Protein (Bogdanov, M., Sun, J., Kaback, H. R., and Dowhan, W. (1996) J. Biol. Chem. 271, 11615–11618)

[Effect of hyperglycemia on glucose uptake of rat mandibular osteoblasts]

PURPOSE

Growing evidence shows an association between diabetes mellitus and alveolar bone loss. As abnormal cellular glucose uptake and metabolism are partly involved in diabetic complications, this study was undertaken to explore the effect of hyperglycemia on glucose uptake, glucose transporter1 (GLUT1) expression induced by insulin of rat mandibular osteoblasts.

METHODS

Primary osteoblasts were isolated and cultured. The cells were incubated for 48h with medium containing 5.5mmol/L and 16.5mmol/L glucose respectively,then treated with or without insulin for 24h. Glucose uptake was detected by using (18)F-FDG in the cells and GLUT1 expression levels were evaluated by Western blotting analysis. One-way ANOVA and t test were performed using SPSS13.0 software package.

RESULTS

The results showed that with 16.5mmol/L glucose, glucose uptake was not changed significantly, but GLUT1 expression was increased by 35% (P<0.01), insulin had no significant effect on glucose uptake, but it decreased GLUT1 expression by 33% (P<0.01).

CONCLUSIONS

It is concluded that hyperglycemia can induce insulin resistance of osteoblasts, in which alteration in transport activity and function of GLUT1 might be involved.

Site-directed alkylation of cysteine to test solvent accessibility of membrane proteins

This protocol describes a detailed method to study the static and dynamic features of membrane proteins, as well as solvent accessibility, by utilizing the lactose permease of Escherichia coli (LacY) as a model. The method relies on the use of functional single-Cys mutants, an affinity tag and a PhosphoImager. The membrane-permeant, radioactive thiol reagent N-[ethyl-1-14C]ethylmaleimide ([14C]NEM) is used to detect site-directed alkylation of engineered single-Cys mutants in situ. The solvent accessibility of the Cys residues is also determined by blockage of [14C]NEM labeling with membrane-impermeant thiol reagents such as methanethiosulfonate ethylsulfonate (MTSES). The labeled proteins are purified by mini-scale affinity chromatography and analyzed by gel electrophoresis. Gels are dried and exposed to a PhosphoImager screen for 1-5 d, and incorporation of radioactivity is visualized. Initial results can be obtained in 24 h.

Golgi GDP-fucose Transporter-deficient Mice Mimic Congenital Disorder of Glycosylation IIc/Leukocyte Adhesion Deficiency II

Modification of glycoproteins by the attachment of fucose residues is widely distributed in nature. The importance of fucosylation has recently been underlined by identification of the monogenetic inherited human disease "congenital disorder of glycosylation IIc," also termed "leukocyte adhesion deficiency II." Due to defective Golgi GDP-fucose transporter (SLC35C1) activity, patients show a hypofucosylation of glycoproteins and present clinically with mental and growth retardation, persistent leukocytosis, and severe infections. To investigate effects induced by the loss of fucosylated structures in different organs, we generated a mouse model for the disease by inactivating the Golgi GDP-transporter gene (Slc35c1). Lectin binding studies revealed a tremendous reduction of fucosylated glycoconjugates in tissues and isolated cells from Slc35c1(-/-) mice. Fucose treatment of cells from different organs led to partial normalization of the fucosylation state of glycoproteins, thereby indicating an alternative GDP-fucose transport mechanism. Slc35c1-deficient mice presented with severe growth retardation, elevated postnatal mortality rate, dilatation of lung alveoles, and hypocellular lymph nodes. In vitro and in vivo leukocyte adhesion and rolling assays revealed a severe impairment of P-, E-, and L-selectin ligand function. The diversity of these phenotypic aspects demonstrates the broad general impact of fucosylation in the mammalian organism.

Intramolecular domain-domain association/dissociation and phosphoryl transfer in the mannitol transporter of Escherichia coli are not coupled

The Escherichia coli mannitol transporter (II(Mtl)) comprises three domains connected by flexible linkers: a transmembrane domain (C) and two cytoplasmic domains (A and B). II(Mtl) catalyzes three successive phosphoryl-transfer reactions: one intermolecular (from histidine phosphocarrier protein to the A domain) and two intramolecular (from the A to the B domain and from the B domain to the incoming sugar bound to the C domain). A key functional requirement of II(Mtl) is that the A and B cytoplasmic domains be able to rapidly associate and dissociate while maintaining reasonably high occupancy of an active stereospecific AB complex to ensure effective phosphoryl transfer along the pathway. We have investigated the rate of intramolecular domain-domain association and dissociation in IIBA(Mtl) by using (1)H relaxation dispersion spectroscopy in the rotating frame. The open, dissociated state (comprising an ensemble of states) and the closed, associated state (comprising the stereospecific complex) are approximately equally populated. The first-order rate constants for intramolecular association and dissociation are 1.7 (+/-0.3) x 10(4) and 1.8 (+/-0.4) x 10(4) s(-1), respectively. These values compare to rate constants of approximately 500 s(-1) for A --> B and B --> A phosphoryl transfer, derived from qualitative line-shape analysis of (1)H-(15)N correlation spectra taken during the course of active catalysis. Thus, on average, approximately 80 association/dissociation events are required to effect a single phosphoryl-transfer reaction. We conclude that intramolecular phosphoryl transfer between the A and B domains of II(Mtl) is rate-limited by chemistry and not by the rate of formation or dissociation of a stereospecific complex in which the active sites are optimally apposed.

Glycogen synthase kinase‐3 is required for optimalde novosynthesis of inositol

Studies have shown that the inositol biosynthetic pathway and the enzyme glycogen synthase kinase-3 (GSK-3) are targets of the mood-stabilizing drugs lithium and valproate. However, a relationship between these targets has not been previously described. We hypothesized that GSK-3 may play a role in inositol synthesis, and that loss of GSK-3 may lead to inositol depletion, thus providing a mechanistic link between the two drug targets. Utilizing a yeast Saccharomyces cerevisiae gsk-3Delta quadruple-null mutant, in which all four genes encoding homologues of mammalian GSK-3 are disrupted, we tested the hypothesis that GSK-3 is required for de novo inositol biosynthesis. The gsk-3Delta mutant exhibited multiple features of inositol depletion, including defective growth in inositol-lacking medium, decreased intracellular inositol, increased INO1 and ITR1 expression, and decreased levels of phosphatidylinositol. Treatment of wild-type cells with a highly specific GSK-3 inhibitor led to a significant increase in INO1 expression. Supplementation with inositol alleviated the temperature sensitivity of gsk-3Delta. Activity of myo-inositol-3 phosphate synthase, the rate-limiting enzyme in inositol de novo biosynthesis, was decreased in gsk-3Delta. These results demonstrate for the first time that GSK-3 is required for optimal myo-inositol-3 phosphate synthase activity and de novo inositol biosynthesis, and that loss of GSK-3 activity causes inositol depletion.

Endothelin-1 impairs glucose transporter trafficking via a membrane-based mechanism

Endothelin-1 (ET-1) disrupts insulin-regulated glucose transporter GLUT4 trafficking. Since the negative consequence of chronic ET-1 exposure appears to be independent of signal disturbance along the insulin receptor substrate-1/phosphatidylinositol (PI) 3-kinase (PI3K)/Akt-2 pathway of insulin action, we tested if ET-1 altered GLUT4 regulation engaged by osmotic shock, a PI3K-independent stimulus that mimics insulin action. Regulation of GLUT4 by hyperosmotic stress was impaired by ET-1. Because of the mutual disruption of both insulin- and hyperosmolarity-stimulated GLUT4 translocation, we tested whether shared signaling and/or key phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated cytoskeletal events of GLUT4 trafficking were targets of ET-1. Both insulin and hyperosmotic stress signaling to Cbl were impaired by ET-1. Also, plasma membrane PIP2 and cortical actin levels were reduced in cells exposed to ET-1. Exogenous PIP2, but not PI 3,4,5-bisphosphate, restored actin structure, Cbl activation, and GLUT4 translocation. These data show that ET-1-induced PIP2/actin disruption impairs GLUT4 trafficking elicited by insulin and hyperosmolarity. In addition to showing for the first time the important role of PIP2-regulated cytoskeletal events in GLUT4 regulation by stimuli other than insulin, these studies reveal a novel function of PIP2/actin structure in signal transduction.

The oligomeric state and stability of the mannitol transporter, EnzymeII(mtl), from Escherichia coli: a fluorescence correlation spectroscopy study

Numerous membrane proteins function as oligomers both at the structural and functional levels. The mannitol transporter from Escherichia coli, EnzymeII(mtl), is a member of the phosphoenolpyruvate-dependent phosphotransferase system. During the transport cycle, mannitol is phosphorylated and released into the cytoplasm as mannitol-1-phosphate. Several studies have shown that EII(mtl) functions as an oligomeric species. However, the oligomerization number and stability of the oligomeric complex during different steps of the catalytic cycle, e.g., substrate binding and/or phosphorylation of the carrier, is still under discussion. In this paper, we have addressed the oligomeric state and stability of EII(mtl) using fluorescence correlation spectroscopy. A functional double-cysteine mutant was site-specifically labeled with either Alexa Fluor 488 or Alexa Fluor 633. The subunit exchange of these two batches of proteins was followed in time during different steps of the catalytic cycle. The most important conclusions are that (1) in a detergent-solubilized state, EII(mtl) is functional as a very stable dimer; (2) the stability of the complex can be manipulated by changing the intermicellar attractive forces between PEG-based detergent micelles; (3) substrate binding destabilizes the complex whereas phosphorylation increases the stability; and (4) substrate binding to the phosphorylated species partly antagonizes the stabilizing effect.

A long-wavelength fluorescent glucose biosensor based on bioconjugates of galactose/glucose binding protein and Nile Red derivatives

BACKGROUND

Fluorescent biosensors based on galactose/glucose binding protein (GGBP) and environmentally sensitive derivatives of the phenoxazine dye Nile Red are described. These biosensors are proposed as the sensing platform for a minimally invasive, continuous glucose monitoring system that can be implanted under the skin and read transdermally using an external fluorometer.

METHODS

To construct the biosensors, the thiol-reactive Nile Red derivatives INR and IANR were prepared and conjugated to GGBP proteins possessing cysteine mutations that were designed for optimal site-specific fluorophore attachment. The attachment sites were selected to maximize the local environment change for attached dyes between the bound and unbound conformations of GGBP.

RESULTS

Fluorescence responses at the selected cysteine sites of GGBP upon binding to glucose showed that the conjugates typically yielded fluorescence emission around 640-650 nm with up to 50% changes in fluorescence intensity. Conjugate E149C/A213C/L238S INR GGBP also displayed glucose binding in the human physiological range (K (D) = 7.4 mM).

CONCLUSIONS

The phenoxazine derivatives fluoresced at longer wavelengths (>600 nm) approaching the near-infrared spectral window, where interference from scattering and tissue absorbance are minimal. Ultimately, we expect that monitoring systems based on GGBP and longwavelength dyes will be implanted for up to 6 months and can be used to transmit information through the skin to an external monitor.

Interaction of pyridostigmine bromide and N,N-diethyl-m-toluamide alone and in combination with P-glycoprotein expressed in Escherichia coli leaky mutant

P-glycoprotein (P-gp), the most extensively studied ATP-binding transporter, functions as a biological barrier by extruding toxic substances and xenobiotics out of the cell. This study was carried out to determine the effect of N,N-diethyl-m-toluamide (DEET) and pyridostigmine bromide (PB), alone and in combination, on P-gp expression using Escherichia coli leaky mutant transformed with Mdr1 gene (pT5-7/mdr1), which codes for P-gp or lactose permease (pT5-7/lacY) as negative control. Also, daunomycin (a known P-gp sustrate) was used as a positive control and reserpine (a known P-gp inhibitor) served as a negative control. An in vitro cell-resistant assay was used to monitor the potential of test compounds to interact with P-gp. Following exposure of the cells to pyridostigmine bromide or daunomycin, P-gp conferred significant resistance against both compounds, while reserpine and DEET significantly inhibited the glycoprotein. Cells were grown in the presence of noncytotoxic concentrations of daunomycin, pyridostigmine bromide, reserpine, or DEET, and membrane fractions were examined by Western immunoblotting for expression of P-gp. Daunomycin induced P-gp expression quantitatively more than pyridostigmine bromide, while reserpine and DEET significantly inhibited P-gp expression in cells harboring mdr1. Photoaffinity labeling experiment performed with the P-gp ligand [125I]iodoarylazidoprazosin demonstrated that compounds that induced or inhibited P-gp transport activity also bound to P-gp. DEET was also found to be a potent inhibitor of P-gp-mediated ATPase activity, whereas pyridostigmine bromide increased P-gp ATPase activity. Cells expressing P-gp or lac permease were exposed to pyridostigmine bromide and DEET, alone and in combination. Noncytotoxic concentrations of DEET significantly inhibited P-gp-mediated resistance against pyridostigmine bromide, resulting in a reduction of the number of effective drug interactions with biological targets. An explanation of these results might be that DEET is a third-generation inhibitor of P-gp; it has high potency and specificity for P-gp, it inhibits hydrolysis of ATP, it exerts no appreciable impact on cytochrome P-450 3A4, and it prevents transport of xenobiotics, such as pyridostigmine bromide, out of the cell. This conclusion explains, at least in part, the increased toxicity and bioavailability of pyridostigmine bromide following combined administration with DEET. This study improves our understanding of the basis of chemical interactions with DEET by defining the ability of drugs to interact with P-gp either as inhibitors or substrates, which may in turn lead to altered efficacy or toxicity.

Effects of N-glycosylation and inositol on the ER stress response in yeast Saccharomyces cerevisiae

IRE1 and HAC1 are essential for the unfolded protein response in the endoplasmic reticulum (ER). IRE1- and HAC1-disruptants require high concentrations of inositol for its normal growth. The ALG6, ALG8, and ALG10 genes encode the glucosyltransferases necessary for the completion of the synthesis of the lipid-linked oligosaccharide used for the asparagine-linked glycosylation of proteins in that order. Here we show that, given a combination of the hac1 defect with a disruption of ALG6, ALG8, and ALG10, no strains grow on inositol-free medium. However, the growth defect of the hac1-alg10 double disrupted was partially, but significantly, suppressed by the addition of inositol to the medium. These results indicate that inositol, according to the numbers of glucose residues in the oligosaccharide, plays an important role in the stress response and quality control of glycoproteins in the ER.

Substrate-induced conformational changes in the membrane-embedded IIC(mtl)-domain of the mannitol permease from Escherichia coli, EnzymeII(mtl), probed by tryptophan phosphorescence spectroscopy

Membrane-bound transport proteins are expected to proceed via different conformational states during the translocation of a solute across the membrane. Tryptophan phosphorescence spectroscopy is one of the most sensitive methods used for detecting conformational changes in proteins. We employed this technique to study substrate-induced conformational changes in the mannitol permease, EnzymeII(mtl), of the phosphoenolpyruvate-dependent phosphotransferase system from Escherichia coli. Ten mutants containing a single tryptophan were engineered in the membrane-embedded IIC(mtl)-domain, harboring the mannitol translocation pathway. The mutants were characterized with respect to steady-state and time-resolved phosphorescence, yielding detailed, site-specific information of the Trp microenvironment and protein conformational homogeneity. The study revealed that the Trp environments vary from apolar, unstructured, and flexible sites to buried, highly homogeneous, rigid peptide cores. The most remarkable example of the latter was observed for position 97, because its long sub-second phosphorescence lifetime and highly structured spectra in both glassy and fluid media imply a well defined and rigid core around the probe that is typical of beta-sheet-rich structural motifs. The addition of mannitol had a large impact on most of the Trp positions studied. In the case of position 97, mannitol binding induced partial unfolding of the rigid protein core. On the contrary, for residue positions 126, 133, and 147, both steady-state and time-resolved data showed that mannitol binding induces a more ordered and homogeneous structure around these residues. The observations are discussed in context of the current mechanistic and structural model of EII(mtl).

Stoichiometry and substrate affinity of the mannitol transporter, EnzymeIImtl, from Escherichia coli

Uptake and consecutive phosphorylation of mannitol in Escherichia coli is catalyzed by the mannitol permease EnzymeIImtl. The substrate is bound at an extracellular-oriented binding site, translocated to an inward-facing site, from where it is phosphorylated, and subsequently released into the cell. Previous studies have shown the presence of both a high- and a low-affinity binding site with K(D)-values in the nano- and micromolar range, respectively. However, reported K(D)-values in literature are highly variable, which casts doubts about the reliability of the measurements and data analysis. Using an optimized binding measurement system, we investigated the discrepancies reported in literature, regarding both the variability in K(D)-values and the binding stoichiometry. By comparing the binding capacity obtained with flow dialysis with different methods to determine the protein concentration (UV-protein absorption, Bradford protein detection, and a LDH-linked protein assay to quantify the number of phosphorylation sites), we proved the existence of only one mannitol binding site per dimeric species of unphosphorylated EnzymeIImtl. Furthermore, the affinity of EnzymeIImtl for mannitol appeared to be dependent on the protein concentration and seemed to reflect the presence of an endogenous ligand. The dependency could be simulated assuming that >50% of the binding sites were occupied with a ligand that shows an affinity for EnzymeIImtl in the same range as mannitol.

A novel mutation (A148V) in the glucose 6-phosphate translocase (SLC37A4) gene in a Korean patient with glycogen storage disease type 1b

We report a Korean patient with glycogen storage disease type 1b (GSD-1b) whose diagnosis was confirmed by liver biopsy and laboratory results. The patient presented with delay of puberty and short stature on admission and had typical clinical symptoms of GSD as well as chronic neutropenia and inflammatory bowel disease. Mutation analysis of the glucose 6-phosphate translocase 6-phosphate translocase (SLC37A4) gene revealed that the patient was a compound heterozygote of two different mutations including a deletion mutation (c.1042_1043delCT; L348fs) and a missense mutation (A148V). The L348fs mutation was inherited from the patient's father and has been reported in an Italian family with GSD-1b, while the A148V mutation was transmitted from the patient's mother and was a novel mutation. To the best of our knowledge, this is the first report of genetically confirmed case of GSD-1b in Korean.

Comparative study of epithelial gene expression in the small intestine among total proctocolectomized, dietary sodium-depleted, and aldosterone-infused rats

We previously demonstrated enhanced plasma aldosterone, ileal activation of epithelial sodium channel (ENaC), and induction of 11 beta-hydroxysteroid dehydrogenase type 2 after total proctocolectomies in rats. However, factors other than circulating aldosterone may cause molecular induction associated with sodium transport. Sprague-Dawley rats were treated with sodium-deficient diets or subcutaneous aldosterone infusion for 4 weeks. Rats also underwent total proctocolectomies as positive control. We extracted epithelial RNA from the distal small intestine and compared mRNA expression of the alpha, beta, and gamma subunits of ENaC, prostasin, sodium glucose transporter 1 (SGLT1), and the alpha1 and beta1 subunits of Na(+)/K(+)-ATPase among control, total proctocolectomized, dietary sodium-depleted, and aldosterone-infused rats by quantitative reverse transcription-polymerase chain reaction or Northern blotting. A significant increase in aldosterone was noted in sodium-depleted and aldosterone-infused rats. The induction of three subunits of ENaC and prostasin mRNA was observed in proctocolectomized, aldosterone-infused rats but not in dietary sodium-depleted rats. The levels of the alpha1 and beta1 subunits of Na(+)/K(+)-ATPase were similar among the experimental groups. SGLT1 mRNA was induced only in proctocolectomized rats. The molecular induction of ENaC, prostasin, and SGLT1 is unique for total proctocolectomized rats. Aldosterone infusion can induce several essential molecules for sodium absorption, as seen in total proctocolectomy.

The First Cytoplasmic Loop of the Mannitol Permease from Escherichia coli is Accessible for Sulfhydryl Reagents from the Periplasmic Side of the Membrane

The mannitol permease (EII(Mtl)) from Escherichia coli couples mannitol transport to phosphorylation of the substrate. Renewed topology prediction of the membrane-embedded C domain suggested that EII(Mtl) contains more membrane-embedded segments than the six proposed previously on the basis of a PhoA fusion study. Cysteine accessibility was used to confirm this notion. Since cysteine 384 in the cytoplasmic B domain is crucial for the phosphorylation activity of EII(Mtl), all cysteine mutants contained this activity-linked cysteine residue in addition to those introduced for probing the membrane topology of the protein. To distinguish between the activity-linked cysteine and the probed cysteine, either trypsin was used to specifically digest the two cytoplasmic domains (A and B), thereby removing Cys384, or Cys384 was protected by phosphorylation from alkylation by N-ethylmaleimide (NEM). Our data show that upon phosphorylation EII(Mtl) undergoes major conformational changes, whereby residues in the putative first cytoplasmic loop become accessible to NEM. Other residues in this loop were accessible to NEM in intact cells and inside-out membrane vesicles, but cysteine residues at these positions only reacted with the membrane-impermeable sulfhydryl reagent from the periplasmic side of the protein. These and other results suggest that the predicted loop between TM2 and TM3 may fold back into the membrane and form part of the translocation path.

Brain contains a functional glucose-6-phosphatase complex capable of endogenous glucose production

Glucose is absolutely essential for the survival and function of the brain. In our current understanding, there is no endogenous glucose production in the brain, and it is totally dependent upon blood glucose. This glucose is generated between meals by the hydrolysis of glucose-6-phosphate (Glc-6-P) in the liver and the kidney. Recently, we reported a ubiquitously expressed Glc-6-P hydrolase, glucose-6-phosphatase-beta (Glc-6-Pase-beta), that can couple with the Glc-6-P transporter to hydrolyze Glc-6-P to glucose in the terminal stages of glycogenolysis and gluconeogenesis. Here we show that astrocytes, the main reservoir of brain glycogen, express both the Glc-6-Pase-beta and Glc-6-P transporter activities and that these activities can couple to form an active Glc-6-Pase complex, suggesting that astrocytes may provide an endogenous source of brain glucose.

The lactose permease ofEscherichia coli: overall structure, the sugar-binding site and the alternating access model for transport

Membrane transport proteins transduce free energy stored in electrochemical ion gradients into a concentration gradient and are a major class of membrane proteins, many of which play important roles in human health and disease. Recently, the X-ray structure of the Escherichia coli lactose permease (LacY), an intensively studied member of a large group of related membrane transport proteins, was solved at 3.5 A. LacY is composed of N- and C-terminal domains, each with six transmembrane helices, symmetrically positioned within the molecule. The structure represents the inward-facing conformation, as evidenced by a large internal hydrophilic cavity open to the cytoplasmic side. The structure with a bound lactose homolog reveals the sugar-binding site in the cavity, and a mechanism for translocation across the membrane is proposed in which the sugar-binding site has alternating accessibility to either side of the membrane.

[Gene therapy in familial amyloidotic polyneuropathy by single-stranded oligonucleotides (SSOs)]

Transthyretin (TTR) related familial amyloidotic polyneuropathy (FAP) is the common form of hereditary generalized amyloidosis and is characterized by the accumulation of amyloid deposits in the peripheral nerves and other organs. Liver transplantation has been utilized as therapy for FAP, because the variant TTR is predominantly synthesized by the liver, but this therapy is associated with several problems. Since we need to develop a new treatment, we examined the feasibility of gene therapy in FAP to prevent the production of variant TTR in the liver by using single-stranded oligonucleotides (SSOs). To examine in vitro and in vivo conversion of the TTR gene by SSOs embedded in atelocollagen, we used HepG2 cells and liver from transgenic mice whose intrinsic wild-type TTR gene was replaced by the mouse TTR V30M gene. The level of gene conversion was determined by real-time RCR combined with mutant-allele-specific amplification. The level of gene conversion was approximately 11% and 9% of the total TTR gene in HepG2 cells and liver from transgenic mice, respectively. Therefore, gene therapy via this method may be a promising alternative to liver transplantation for treatment of FAP.

The cellular fate of glucose and its relevance in type 2 diabetes

Type 2 diabetes is a complex disorder with diminished insulin secretion and insulin action contributing to the hyperglycemia and wide range of metabolic defects that underlie the disease. The contribution of glucose metabolic pathways per se in the pathogenesis of the disease remains unclear. The cellular fate of glucose begins with glucose transport and phosphorylation. Subsequent pathways of glucose utilization include aerobic and anaerobic glycolysis, glycogen formation, and conversion to other intermediates in the hexose phosphate or hexosamine biosynthesis pathways. Abnormalities in each pathway may occur in diabetic subjects; however, it is unclear whether perturbations in these may lead to diabetes or are a consequence of the multiple metabolic abnormalities found in the disease. This review is focused on the cellular fate of glucose and relevance to human type 2 diabetes.

Homology modeling of the human microsomal glucose 6-phosphate transporter explains the mutations that cause the glycogen storage disease type Ib

Glycogen storage disease type Ib is caused by mutations in the glucose 6-phosphate transporter (G6PT) in the endoplasmic reticulum membrane in liver and kidney. Twenty-eight missense and two deletion mutations that cause the disease were previously shown to reduce or abolish the transporter's activity. However, the mechanisms by which these mutations impair transport remain unknown. On the basis of the recently determined crystal structure of its Escherichia coli homologue, the glycerol 3-phosphate transporter, we built a three-dimensional structural model of human G6PT by homology modeling. G6PT is proposed to consist of 12 transmembrane alpha-helices that are divided into N- and C-terminal domains, with the substrate-translocation pore located between the two domains and the substrate-binding site formed by R28 and K240 at the domain interface. The disease-causing mutations were found to occur at four types of positions: (I) in the substrate-translocation pore, (II) at the N-/C-terminal domain interface, (III) in the interior of the N- and C-terminal domains, and (IV) on the protein surface. Whereas class I mutations affect substrate binding directly, class II mutations, mostly involving changes in side chain size, charge, or both, hinder the conformational change required for substrate translocation. On the other hand, class III and class IV mutations, often introducing a charged residue into a helix bundle or at the protein-lipid interface, probably destabilize the protein. These results also suggest that G6PT operates by a similar antiport mechanism as its E. coli homologue, namely, the substrate binds at the N- and C-terminal domain interface and is then transported across the membrane via a rocker-switch type of movement of the two domains.

Three-dimensional Solution Structure of the Cytoplasmic B Domain of the Mannitol Transporter IIMannitol of the Escherichia coli Phosphotransferase System

The solution structure of the cytoplasmic B domain of the mannitol (Mtl) transporter (II(Mtl)) from the mannitol branch of the Escherichia coli phosphotransferase system has been solved by multidimensional NMR spectroscopy with extensive use of residual dipolar couplings. The ordered IIB(Mtl) domain (residues 375-471 of II(Mtl)) consists of a four-stranded parallel beta-sheet flanked by two helices (alpha(1) and alpha(3)) on one face and helix alpha(2) on the opposite face with a characteristic Rossmann fold comprising two right-handed beta(1)alpha(1)beta(2) and beta(3)alpha(2)beta(4) motifs. The active site loop is structurally very similar to that of the eukaryotic protein tyrosine phosphatases, with the active site cysteine (Cys-384) primed in the thiolate state (pK(a) < 5.6) for nucleophilic attack at the phosphorylated histidine (His-554) of the IIA(Mtl) domain through stabilization by hydrogen bonding interactions with neighboring backbone amide groups at positions i + 2/3/4 from Cys-384 and with the hydroxyl group of Ser-391 at position i + 7. Modeling of the phosphorylated state of IIB(Mtl) suggests that the phosphoryl group can be readily stabilized by hydrogen bonding interactions with backbone amides in the i + 2/4/5/6/7 positions as well as with the hydroxyl group of Ser390 at position i + 6. Despite the absence of any significant sequence identity, the structure of IIB(Mtl) is remarkably similar to the structures of bovine protein tyrosine phosphatase (which contains two long insertions relative to IIB(Mtl)) and the cytoplasmic B component of enzyme II(Chb), which fulfills an analogous role to IIB(Mtl) in the N,N'-diacetylchitobiose branch of the phosphotransferase system. All three proteins utilize a cysteine residue in the nucleophilic attack of a phosphoryl group covalently bound to another protein.

Realization and Characterization of Porous Gold for Increased Protein Coverage on Acoustic Sensors

Immunosensors show great potential for the direct detection of biological molecules. The sensitivity of these affinity-based biosensors is dictated by the amount of receptor molecules immobilized on the sensor surface. An enlargement of the sensor area would allow for an increase of the binding capacity, hence a larger amount of immobilized receptor molecules. To this end, we use electrochemically deposited "gold black" as a porous sensor surface for the immobilization of proteins. In this paper, we have analyzed the different parameters that define the electrochemical growth of porous gold, starting from flat gold surfaces, using different characterization techniques. Applied potentials of -0.5 V versus a reference electrode were found to constitute the most adequate conditions to grow porous gold surfaces. Using cyclic voltammetry, a 16 times increase of the surface area was observed under these electrochemical deposition conditions. In addition, we have assessed the immobilization degree of alkanethiols and of proteins on these different porous surfaces. The optimized deposition conditions for realizing porous gold substrates lead to a 11.4-fold increase of thiol adsorption and a 3.3-fold increase of protein adsorption, using the quartz crystal microbalance (QCM-D) as a biological transducer system. Hence, it follows that the high specific area of the porous gold can amplify the final sensitivity of the original flat surface device.

Engineering Lactococcus lactis for production of mannitol: high yields from food-grade strains deficient in lactate dehydrogenase and the mannitol transport system

Mannitol is a sugar polyol claimed to have health-promoting properties. A mannitol-producing strain of Lactococcus lactis was obtained by disruption of two genes of the phosphoenolpyruvate (PEP)-mannitol phosphotransferase system (PTS(Mtl)). Genes mtlA and mtlF were independently deleted by double-crossover recombination in strain L. lactis FI9630 (a food-grade lactate dehydrogenase-deficient strain derived from MG1363), yielding two mutant (Delta ldh Delta mtlA and Delta ldh Delta mtlF) strains. The new strains, FI10091 and FI10089, respectively, do not possess any selection marker and are suitable for use in the food industry. The metabolism of glucose in nongrowing cell suspensions of the mutant strains was characterized by in vivo (13)C-nuclear magnetic resonance. The intermediate metabolite, mannitol-1-phosphate, accumulated intracellularly to high levels (up to 76 mM). Mannitol was a major end product, one-third of glucose being converted to this hexitol. The double mutants, in contrast to the parent strain, were unable to utilize mannitol even after glucose depletion, showing that mannitol was taken up exclusively by PEP-PTS(Mtl). Disruption of this system completely blocked mannitol transport in L. lactis, as intended. In addition to mannitol, approximately equimolar amounts of ethanol, 2,3-butanediol, and lactate were produced. A mixed-acid fermentation (formate, ethanol, and acetate) was also observed during growth under controlled conditions of pH and temperature, but mannitol production was low. The reasons for the alteration in the pattern of end products under nongrowing and growing conditions are discussed, and strategies to improve mannitol production during growth are proposed.

Selective stimulation of G-6-Pase catalytic subunit but not G-6-P transporter gene expression by glucagon in vivo and cAMP in situ

We recently compared the regulation of glucose-6-phosphatase (G-6-Pase) catalytic subunit and glucose 6-phosphate (G-6-P) transporter gene expression by insulin in conscious dogs in vivo (Hornbuckle LA, Edgerton DS, Ayala JE, Svitek CA, Neal DW, Cardin S, Cherrington AD, and O'Brien RM. Am J Physiol Endocrinol Metab 281: E713-E725, 2001). In pancreatic-clamped, euglycemic conscious dogs, a 5-h period of hypoinsulinemia led to a marked increase in hepatic G-6-Pase catalytic subunit mRNA; however, G-6-P transporter mRNA was unchanged. Here, we demonstrate, again using pancreatic-clamped, conscious dogs, that glucagon is a candidate for the factor responsible for this selective induction. Thus glucagon stimulated G-6-Pase catalytic subunit but not G-6-P transporter gene expression in vivo. Furthermore, cAMP stimulated endogenous G-6-Pase catalytic subunit gene expression in HepG2 cells but had no effect on G-6-P transporter gene expression. The cAMP response element (CRE) that mediates this induction was identified through transient transfection of HepG2 cells with G-6-Pase catalytic subunit-chloramphenicol acetyltransferase fusion genes. Gel retardation assays demonstrate that this CRE binds several transcription factors including CRE-binding protein and CCAAT enhancer-binding protein.

In vivo synthesized proteins with monoexponential fluorescence decay kinetics

Tryptophan, when in a protein, typically shows multiexponential fluorescence decay kinetics. Complex kinetics prevents a straightforward interpretation of time-resolved fluorescence protein data, particularly in anisotropy studies or if the effect of a dynamic quencher or a resonance energy transfer (RET) acceptor is investigated. Here, time-resolved fluorescence data are presented of an isosteric tryptophan analogue, 5-fluorotryptophan, which when biosynthetically incorporated in proteins shows monoexponential decay kinetics. Data are presented indicating that the presence of a fluoro atom at the 5-position suppresses the electron transfer rate from the excited indole moiety to the peptide bond. This process has been related to the multiexponential fluorescence decay of tryptophan in proteins. The monoexponential decay of 5-fluorotryptophan makes it possible to measure simultaneously multiple distances between 5-fluorotryptophan and a RET acceptor. We demonstrate that for an oligomeric protein, consisting of two single-tryptophan-containing subunits, the individual distances between 5-fluorotryptophan and the single substrate binding site can be resolved using a substrate harboring a RET acceptor.

Improved neutrophil function in a glycogen storage disease type 1b patient after liver transplantation

Patients with glycogen storage disease type 1b (GSD1b) not only show hepatomegaly, hypoglycaemia and lactic acidosis, but also neutropenia and neutrophil dysfunction. Here, we report improvement of neutropenia and neutrophil function in a 22-year-old male GSD1b patient who had undergone living-related partial liver transplantation (LT) at 18 years of age. After LT, the patient's infectious episodes decreased, gastrointestinal symptoms ameliorated, neutrophil counts increased, and neutrophil function tests normalised.

CONCLUSION

Although it is not known whether this improvement was causally related to liver transplantation, this may be the first recorded case of restoration of neutrophil dysfunction in a glycogen storage disease type 1b patient.

Prolonged maltose-limited cultivation of Saccharomyces cerevisiae selects for cells with improved maltose affinity and hypersensitivity

Prolonged cultivation (>25 generations) of Saccharomyces cerevisiae in aerobic, maltose-limited chemostat cultures led to profound physiological changes. Maltose hypersensitivity was observed when cells from prolonged cultivations were suddenly exposed to excess maltose. This substrate hypersensitivity was evident from massive cell lysis and loss of viability. During prolonged cultivation at a fixed specific growth rate, the affinity for the growth-limiting nutrient (i.e., maltose) increased, as evident from a decreasing residual maltose concentration. Furthermore, the capacity of maltose-dependent proton uptake increased up to 2.5-fold during prolonged cultivation. Genome-wide transcriptome analysis showed that the increased maltose transport capacity was not primarily due to increased transcript levels of maltose-permease genes upon prolonged cultivation. We propose that selection for improved substrate affinity (ratio of maximum substrate consumption rate and substrate saturation constant) in maltose-limited cultures leads to selection for cells with an increased capacity for maltose uptake. At the same time, the accumulative nature of maltose-proton symport in S. cerevisiae leads to unrestricted uptake when maltose-adapted cells are exposed to a substrate excess. These changes were retained after isolation of individual cell lines from the chemostat cultures and nonselective cultivation, indicating that mutations were involved. The observed trade-off between substrate affinity and substrate tolerance may be relevant for metabolic engineering and strain selection for utilization of substrates that are taken up by proton symport.