DUG is a novel homologue of translation initiation factor 4G that binds eIF4A

To elucidate the molecular mechanisms of cell death, we have cloned a new gene, designated death-upregulated gene (DUG), from rat insulinoma cells. DUG is constitutively expressed at very low levels in normal cells but is dramatically upregulated in apoptotic cells following serum/glucose starvation or death receptor ligation by Fas ligand. The DUG mRNA is present in two splicing forms: a long form that encodes a protein of 469 amino acids and a short form that gives rise to a polypeptide of 432 amino acids. The predicted DUG protein sequence contains two putative nuclear localization signals and multiple phosphorylation sites for protein kinases and two conserved MA3 domains. Importantly, DUG is homologous to eukaryotic translation initiation factor (eIF) 4G and binds to eIF4A presumably through MA3 domains. Upon transfection, DUG inhibits both intrinsic and extrinsic pathways of apoptosis. Thus, DUG is a novel homologue of eIF4G that regulates apoptosis.     

The contribution of photosynthetic pigments to the development of biochemical separation methods: 1900–1980

The role of photosynthetic pigments in the development of separation methods in biochemistry during the period 1900-1980 is described beginning with M. Tswett who introduced separation of chlorophylls and carotenoids on columns and coined the term chromatography in 1906. In Uppsala, T. Svedberg developed the ultracentrifuge in the 1920s. A. Tiselius improved electrophoresis in the 1930s and developed chromatography of proteins in the 1940s and 1950s. Others of 'The Uppsala school in separation science' include J. Porath, P. Flodin and S. Hjertén who further developed various gel chromatographic methods. Hjertén introduced free zone electrophoresis in narrow tubes, a forerunner of capillary electrophoresis. Two proteins, phycoerythrin and phycocyanin, were used as test substances in all these methodological studies. Aqueous two-phase partitioning as a separation method was introduced in 1956 by the author. In this work, chloroplast particles were used, and the method was applied for the separation and purification of intact chloroplasts, inside-out thylakoid vesicles and plasma membranes. My research was carried out in cooperation with G. Blomquist, G. Johansson, C. Larsson, B. Andersson and H.-E. Akerlund during a 20-year period, 1960-1980.     

Hormone replacement therapy in rheumatoid arthritis is associated with lower serum levels of soluble IL-6 receptor and higher insulin-like growth factor 1

Hormone replacement therapy (HRT) modulates the imbalance in bone remodeling, thereby decreasing bone loss. Sex hormones are known to influence rheumatic diseases. The aim of this study was to investigate the effects of HRT on the serum levels of hormones and cytokines regulating bone turnover in 88 postmenopausal women with active rheumatoid arthritis (RA) randomly allocated to receive HRT plus calcium and vitamin D3 or calcium and vitamin D3 alone for 2 years. An increase in estradiol (E2) correlated strongly with improvement of bone mineral density in the hip (P < 0.001) and lumbar spine (P < 0.001). Both baseline levels and changes during the study of IL-6 and erythrocyte sedimentation rate were correlated positively (P < 0.001). HRT for 2 years resulted in an increase of the bone anabolic factor, insulin-like growth factor 1 (IGF-1) (P < 0.05) and a decrease of serum levels of soluble IL-6 receptor (sIL-6R) (P < 0.05), which is known to enhance the biological activity of IL-6, an osteoclast-stimulating and proinflammatory cytokine. Baseline levels of IL-6 and IGF-1 were inversely associated (P < 0.05), and elevation of IGF-1 was connected with decrease in erythrocyte sedimentation rate (P < 0.05) after 2 years. Interestingly, increase in serum levels of E2 was associated with reduction of sIL-6R (P < 0.05) and reduction of sIL-6R was correlated with improved bone mineral density in the lumbar spine (P < 0.05). The latter association was however not significant after adjusting for the effect of E2 (P = 0.075). The influences of IGF-1 and the IL-6/sIL-6R pathways suggest possible mechanisms whereby HRT may exert beneficial effects in RA. However, to confirm this hypothesis future and larger studies are needed.     

Inactivation of the glycine transporter 1 gene discloses vital role of glial glycine uptake in glycinergic inhibition

The glycine transporter subtype 1 (GlyT1) is widely expressed in astroglial cells throughout the mammalian central nervous system and has been implicated in the regulation of N-methyl-D-aspartate (NMDA) receptor activity. Newborn mice deficient in GlyT1 are anatomically normal but show severe motor and respiratory deficits and die during the first postnatal day. In brainstem slices from GlyT1-deficient mice, in vitro respiratory activity is strikingly reduced but normalized by the glycine receptor (GlyR) antagonist strychnine. Conversely, glycine or the GlyT1 inhibitor sarcosine suppress respiratory activity in slices from wild-type mice. Thus, during early postnatal life, GlyT1 is essential for regulating glycine concentrations at inhibitory GlyRs, and GlyT1 deletion generates symptoms found in human glycine encephalopathy.     

Effects of transforming growth factor β1 expression in a rat colon carcinoma: growth inhibition, leukocyte infiltration and production of interleukin-10 and tumor necrosis factor α

The cytokine transforming growth factor β-1 (TGFβ1), was transfected into a TGFβ1-negative rat colon carcinoma. The growth of isografts of TGFβ1-expressing tumors was compared to that of vector control transfectants. The TGFβ1 transfectant grew significantly more slowly after intrahepatic isografting than did vector control and wild-type tumors. The TGFβ1-transfected tumor tissue had significantly greater infiltration of both CD4⁺ and CD8⁺ T lymphocytes than did the vector control tumor. The tumor-infiltrating leukocytes (TIL) from TGFβ1-transfected tumor secreted significantly more of the cytokines interleukin-10 (IL-10) and tumor necrosis factor α (TNFα) than did TIL from the vector control tumor. The TGFβ1 transfectant also demonstrated a significantly slower outgrowth in immunodeficient SCID mice, supporting a non-T-lymphocyte-dependent mechanism for the tumor retardation. In SCID mice, the TGFβ1-transfected tumor demonstrated significantly greater infiltration of both granulocytes and macrophages than did the vector control transfectant. We also demonstrated a direct inhibitory effect of rat TNFα on tumor proliferation in vitro. These results suggest that TGFβ1 induces a local secretion of immunomodulating cytokines and that this may influence monocytes, lymphocytes and granulocytes to retard tumor outgrowth. Received: 7 July 1999 / Accepted: 12 August 1999     

Protein phosphatase 2A holoenzyme and its subunits from Medicago sativa

We detected an about 200 kDa holoenzyme of protein phosphatase 2A (PP2A) in the crude extract of Medicago sativa microcallus cells by gel permeation chromatography. By polymerase chain reaction (PCR) we isolated two M. sativa cDNA fragments corresponding to the catalytic (C) subunit, and one each coding for the A and the B regulatory subunits of PP2A. The C subunit sequences were different from that published previously, indicating the existence of at least three different isoforms in M. sativa. Using the PCR fragments as probes, we obtained two distinct full-length clones for both the A and B subunits from an alfalfa cDNA library. Our results demonstrate that the components of the PP2A holoenzyme, namely the catalytic and regulatory subunits, are present in alfalfa in several isoforms and that their sequences are highly similar to their plant, yeast and animal counterparts. The distinct regulatory subunit genes are constitutively expressed during the cell cycle. Interestingly, two A-B subunit pairs had parallel mRNA steady-state levels in different plant tissues suggesting that not all of the possible isoform combinations are present in all tissues. The expression of the MsPP2A B subunit form was induced by abscisic acid indicating a specific function for this protein in the stress response.     

Supression of hemin-mediated oxidation of low-density lipoprotein and subsequent endothelial reactions by hydrogen sulfide (H2S)

Heme-mediated oxidative modification of low-density lipoprotein (LDL) plays a crucial role in early atherogenesis. It has been shown that hydrogen sulfide (H₂S) produced by vascular smooth muscle cells is present in plasma at a concentration of about 50 µmol/L. H₂S is a strong reductant which can react with reactive oxygen species like superoxide anion and hydrogen peroxide. The current study investigated the effect of H₂S on hemin-mediated oxidation of LDL and oxidized LDL (oxLDL)-induced endothelial reactions. H₂S dose dependently delayed the accumulation of lipid peroxidation products—conjugated dienes, lipid hydroperoxides (LOOH), and thiobarbituric acid reactive substances—during hemin-mediated oxidation. Moreover, H₂S decreased the LOOH content of both oxidized LDL and lipid extracts derived from soft atherosclerotic plaque, which was accompanied by reduced cytotoxicity. OxLDL-mediated induction of the oxidative stress responsive gene, heme oxygenase-1, was also abolished by H₂S. Finally we have shown that H₂S can directly protect endothelium against hydrogen peroxide and oxLDL-mediated endothelial cytotoxicity. These results demonstrate novel functions of H₂S in preventing hemin-mediated oxidative modification of LDL, and consequent deleterious effects, suggesting a possible antiatherogenic action of H₂S.