A new class of Spiegelmers containing 2'-fluoro-nucleotides

Synthesis of 2'-fluoro-nucleosides from L-arabinose in order to perform the synthesis of 2'-fluoro-Spiegelmers binding to a neuropeptide.

Differential regulation of endogenous glucose-6-phosphatase and phosphoenolpyruvate carboxykinase gene expression by the forkhead transcription factor FKHR in H4IIE-hepatoma cells

The insulin responsive H4IIEC3 rat hepatoma cell line (H4 cells) was used in order to determine the role of the transcription factor FKHR in the regulation of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Both PEPCK and G6Pase contain putative FKHR binding sites in their promoter sequence. Using a retroviral expression system, we stably overexpressed FKHR in H4-cells. FKHR was phosphorylated in a PI 3-kinase- and Akt-dependent manner, and was translocated from the nucleus to the cytoplasm in response to insulin. Furthermore, overexpression of FKHR markedly increased the expression of the catalytic subunit of G6Pase (basal about 2.5-fold, dexamethasone/cAMP stimulated about fivefold, respectively). In contrast, both basal and dexamethasone/cAMP-induced levels of PEPCK mRNA were unaffected by FKHR-overexpression. These data suggest a specific function for FKHR in the regulation of hepatic gluconeogenesis at the level of G6Pase, but not PEPCK gene expression.

PSCA expression is regulated by phorbol ester and cell adhesion in the bladder carcinoma cell line RT112

The expression of the surface protein prostate stem cell antigen (PSCA) in prostate carcinoma increases in parallel with the progression of the tumor. In contrast, we have recently shown that PSCA expression is reduced or undetectable in other types of undifferentiated tumors. To elucidate the cellular mechanisms that underlie this complex pattern of expression, we studied regulatory parameters for PSCA expression in the bladder carcinoma cell line RT112 by Northern analysis. PSCA gene expression was stimulated by a culture dish surface that caused aggregation of cells, suggesting that its expression is regulated by mechanisms related to the adhesion of epithelial cells. Phorbol ester markedly stimulated PSCA gene expression in a cycloheximide- and actinomycin-inhibitable manner after a lag phase of 10 h, indicating that transcription of the PSCA gene is regulated by protein kinase C and a newly synthesized protein. In contrast, epidermal growth factor, platelet-derived growth factor (PDGF)-BB, tumor necrosis factor-alpha, interferon-gamma or a slightly lowered pH failed to increase PSCA mRNA levels. Consistent with the variable expression of PSCA in different tumors, our analysis in RT112 cells shows that its expression is controlled by a strongly inducible promoter that is specifically regulated by extracellular signals.

Quantitative trait loci for obesity and insulin resistance (Nob1, Nob2) and their interaction with the leptin receptor allele (LeprA720T/T1044I) in New Zealand obese mice

AIMS/HYPOTHESIS

To locate genes responsible for obesity and insulin resistance, a backcross model of New Zealand obese (NZO) mice with the lean Swiss/Jackson Laboratory (SJL) strain was stablished.

RESULTS

In female NZO x F1 backcross mice, two major quantitative trait loci for variables of obesity (body weight, body mass index, total body fat) and insulin resistance (hyperinsulinaemia) were identified on chromosomes 5 (Nob1) and 19 (Nob2) close to the markers D5Mit392 and D19Mit91. The aberrant alleles have presumably contributed by the NZO genome. Whereas Nob1 contributed mainly to higher body weight, Nob2 seemed to mainly aggravate insulin resistance independent of obesity. The leptin receptor variant of NZO (LeprA720T/T1044I) failed to alter any of the variables of obesity. It seemed, however, to enhance the effect of Nob1 on body weight and that of Nob2 on serum insulin concentration. When expressed in COS-7 cells, LeprA720T/T10441 produced a normal basal and maximum activation with a minor increase in the EC50 of leptin.

CONCLUSIONS/INTERPRETATION

The data identify two new quantitative trait loci that are responsible for a major part of obesity and hyperinsulinaemia as produced by recessive genes in NZO mice. LeprA720T/T1044I alone cannot produce obesity, but may enhance the effects of other obesity/insulin resistance genes in this mouse model.

Reduced expression of PSCA, a member of the LY-6 family of cell surface antigens, in bladder, esophagus, and stomach tumors

Prostate stem cell antigen (PSCA) is a member of the LY-6 family of surface proteins that is overexpressed in prostate cancer. Using serial analysis of gene expression (SAGE), we identified PSCA as one of the most abundant transcripts in a differentiated urothelial tumor. As assessed by Northern blotting, PSCA is highly expressed in normal urothelium and noninvasive urothelial tumors. In contrast to the previously reported overexpression of PSCA in progressive and invasive forms of prostate cancer, we found a markedly reduced expression in undifferentiated bladder carcinoma. In addition, several aberrant splicing products derived from the PSCA gene were found in urothelial tumors. Furthermore, PSCA mRNA was highly abundant in normal esophagus and stomach, but was undetectable in esophageal or gastric tumors. The PSCA expression appeared to depend on cell contact, since mRNA levels were increased when RT112 bladder carcinoma cells were grown to confluence. Our data suggest that PSCA could serve as a potential marker for the early carcinogenesis in urothelial and gastric tissues and that its expression is specific for epithelial cells.

GLUT8, a novel member of the sugar transport facilitator family with glucose transport activity

GLUT8 is a novel glucose transporter-like protein that exhibits significant sequence similarity with the members of the sugar transport facilitator family (29.4% of amino acids identical with GLUT1). Human and mouse sequence (86.2% identical amino acids) comprise 12 putative membrane-spanning helices and several conserved motifs (sugar transporter signatures), which have previously been shown to be essential for transport activity, e.g. GRK in loop 2, PETPR in loop 6, QQLSGVN in helix 7, DRAGRR in loop 8, GWGPIPW in helix 10, and PETKG in the C-terminal tail. An expressed sequence tag (STS A005N15) corresponding with the 3'-untranslated region of GLUT8 has previously been mapped to human chromosome 9. COS-7 cells transfected with GLUT8 cDNA expressed a 42-kDa protein exhibiting specific, glucose-inhibitable cytochalasin B binding (K(D) = 56.6 +/- 18 nm) and reconstitutable glucose transport activity (8.1 +/- 1. 4 nmol/(mg protein x 10 s) versus 1.1 +/- 0.1 in control transfections). In human tissues, a 2.4-kilobase pair transcript was predominantly found in testis, but not in testicular carcinoma. Lower amounts of the mRNA were detected in most other tissues including skeletal muscle, heart, small intestine, and brain. GLUT8 mRNA was found in testis from adult, but not from prepubertal rats; its expression in human testis was suppressed by estrogen treatment. It is concluded that GLUT8 is a sugar transport facilitator with glucose transport activity and a hormonally regulated testicular function.

NADH: ubiquinone oxidoreductase in obligate aerobic yeasts

The strictly aerobic yeasts Candida pinus, Cryptococcus albidus, Rhodotorula minuta, Rhodotorula mucilaginosa and Trichosporon beigelii possess mitochondrial NADH dehydrogenases with significant features of the NADH:ubiquinone oxidoreductase (complex I). These species show in all growth phases and under standard cultivation conditions, NADH dehydrogenases of approximately 700 kDa, which are sensitive to rotenone, a specific inhibitor of this complex. Identical results were obtained with the weakly fermenting C. pinus. The facultatively fermenting yeasts Saccharomyces cerevisiae and Kluyveromyces marxianus do not possess the 700 kDa-complex and are insensitive to rotenone. In S. cerevisiae, a rotenone-insensitive NADH dehydrogenase of about 500-600 kDa is detected only in stationary phase cells. As in Neurospora crassa, upon incubation of the obligately aerobic yeast R. mucilaginosa with chloramphenicol, an intermediate NADH dehydrogenase of approximately 350 kDa was formed, which was insensitive to rotenone.