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  • 1.
    Arkhammar, P.
    et al.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Juntti-Berggren, L.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Larsson, O.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Welsh, M.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Nånberg, Eewa
    Department of Medical Cell Biology, Biomedical Center, Uppsala University, Box 571, S-751 23 Uppsala, Sweden; Department of Pathology, University Hospital, Uppsala, Sweden.
    Sjöholm, A.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Köhler, M.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Berggren, P. O.
    Department of Endocrinology, Karolinska Institute, Rolf Luft Center for Diabetes Research, Karolinska Hospital, Stockholm, Sweden.
    Protein kinase C modulates the insulin secretory process by maintaining a proper function of the beta-cell voltage-activated Ca2+ channels1994In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 269, no 4, p. 2743-2749Article in journal (Refereed)
    Abstract [en]

    In the present study an attempt was made to further elucidate the molecular mechanisms whereby protein kinase C (PKC) modulates the beta-cell stimulus-secretion coupling. Regulation of Ca2+ channel activity, [Ca2+]i, and insulin release were investigated in both normal pancreatic mouse beta-cells and in similar beta-cells deprived of PKC activity. [Ca2+]i was measured with the intracellular fluorescent Ca2+ indicator fura-2 and the Ca2+ channel activity was estimated by the whole cell configuration of the patch-clamp technique. To reveal the various isoenzymes of PKC present in the mouse beta-cell, proteins were separated by one-dimensional gel electrophoresis and Western blotting was performed. The production of inositol phosphates was measured by ion-exchange chromatography and insulin release was measured radioimmunologically. Acute stimulation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate resulted in suppression of both the carbamylcholine-induced increase in [Ca2+]i and production of inositol 1,4,5-trisphosphate. Under these conditions the increase in [Ca2+]i in response to glucose was similar to that found in control cells. When beta-cells were deprived of PKC, by exposure to 200 nM 12-O-tetradecanoylphorbol-13-acetate for 24-48 h, there was an enhanced response to carbamylcholine. This response constituted increases in both the [Ca2+]i signal and production of inositol 1,4,5-trisphosphate. Interestingly, cells with down-regulated PKC activity responded more slowly to glucose stimulation, when comparing the initial increase in [Ca2+]i, than control cells. On the other hand, the maximal increase in [Ca2+]i was similar whether or not PKC was present. Moreover, PKC down-regulated cells exhibited a significant reduction of maximal whole cell Ca2+ currents, a finding that may explain the altered kinetics with regard to the [Ca2+]i increase in response to the sugar. Both the alpha and beta 1 forms of the PKC isoenzymes were present in the mouse beta-cell and were also subjected to PKC down-regulation. Hence, either of these isoenzymes or both may be involved in the modulation of phospholipase C and Ca2+ channel activity. Since insulin release under physiological conditions is critically dependent on Ca(2+)-influx through the voltage-gated L-type Ca2+ channels, the kinetics of hormone release was expected to demonstrate a similar delay as that of the [Ca2+]i increase. Although not as pronounced, such a delay was indeed also observed in the onset of insulin release. There was, however, no effect on the total amounts of hormone released. There was,h  owever, no effect on thet  otal amounts of hormone  released.  The present study con- firms that PKC has multiple roles and thereby interacta at different sites  in  the complex series of events consti- tuting  the #?-cell signal-transduction pathway. It is sug- gested that PKC  may  be tonically active and effective in  the maintenance of the phosphorylation state of the voltage-gated  L-type  Ca2+ channel, enabling an appro- priate function of this channel in the insulin secretory process.

  • 2. Brooks, Andrew J
    et al.
    Johansson, Magnus
    John, Anna V
    Xu, Yibin
    Jans, David A
    Vasudevan, Subhash G
    The interdomain region of dengue NS5 protein that binds to the viral helicase NS3 contains independently functional importin beta 1 and importin alpha/beta-recognized nuclear localization signals2002In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 277, no 39, p. 36399-36407Article in journal (Refereed)
    Abstract [en]

    Dengue virus NS5 protein is a multifunctional RNA-dependent RNA polymerase that is essential for virus replication. We have shown previously that the 37- amino acid interdomain spacer sequence (residues (369)X(2)KKX(14)KKKX(11)RKX(3)405) of Dengue2 NS5 contains a functional nuclear localization signal (NLS). In this study, beta-galactosidase fusion proteins carrying point mutations of the positively charged residues or truncations of the interdomain linker region (residues 369-389 or residues 386-405) were analyzed for nuclear import and importin binding activities to show that the N-terminal part of the linker region (residues 369-389, a/bNLS) is critical for nuclear localization and is recognized with high affinity by the conventional NLS-binding importin alpha/beta heterodimeric nuclear import receptor. We also show that the importin beta-binding site (residues 320-368, bNLS) adjacent to the a/bNLS, previously identified by yeast two-hybrid analysis, is functional as an NLS, recognized with high affinity by importin beta, and able to target beta-galactosidase to the nucleus. Intriguingly, the bNLS is highly conserved among Dengue and related flaviviruses, implying a general role for the region and importin beta in the infectious cycle.

  • 3.
    Connolly, Eamonn
    et al.
    The Wenner-Gren Institute, University of Stockholm, Stockholm, Sweden.
    Nånberg, Eewa
    The Wenner-Gren Institute, University of Stockholm, Stockholm, Sweden.
    Nedergaard, Jan
    The Wenner-Gren Institute, University of Stockholm, Stockholm, Sweden.
    Norepinephrine-induced Na+ influx in brown adipocytes is cyclic AMP-mediated1986In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 261, no 31, p. 14377-14385Article in journal (Refereed)
    Abstract [en]

    To examine the involvement of Na+ ions in adrenergic responses in brown adipose tissue, a method is described for measuring Na+ influx into isolated brown adipocytes, using short (30 s) incubations with 22Na+, followed by a two-step centrifugation recovery procedure. Using this method, a clear norepinephrine-stimulated accumulation of intracellular 22Na+ was observed, which was enhanced by the addition of ouabain, was insensitive to amiloride (a Na+/H+ exchange blocker), and could not be mimicked by the total removal of oxygen from the incubation medium. The norepinephrine-stimulated Na+ influx was dose-dependent for the hormone with an EC50 of 250 nM, was blocked by the beta-antagonist propranolol but not by the alpha 1-antagonist prazosin, and could be induced by adrenergic agonists with the order of potency: isoproterenol greater than norepinephrine greater than phenylephrine, indicating a beta-receptor-mediated process. The Na+ influx was found to be cAMP-dependent since it could be induced by both theophylline (a phosphodiesterase inhibitor) and forskolin (an adenylate cyclase activator), but it was independent of other known cellular cAMP-dependent responses since neither addition of fatty acid substrates (octanoate or palmitate), nor of the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone could induce the phenomenon, despite having significant stimulatory effects on cellular respiration. Furthermore, total respiratory inhibition with rotenone, or total oxygen depletion of the medium with dithionite, did not prevent the normal norepinephrine-induced Na+ influx. The possibility that this beta-mediated norepinephrine-stimulated Na+ influx plays an important physiological role in brown adipose tissue activity is discussed, perhaps as one of the, as yet undefined, signals initiating tissue growth in the chronically beta-stimulated tissue of animals facing long-term increases in thermogenic demands.

  • 4.
    Eriksson, Anders
    et al.
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Nånberg, Eewa
    Department of Pathology, University Hospital, Uppsala, Sweden.
    Rönnstrand, Lars
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Engström, Ulla
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Hellman, Ulf
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Rupp, Eva
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Carpenter, Graham
    Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, Tennessee.
    Heldin, Carl-Henrik
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Claesson-Welsh, Lena
    Ludwig Institute for Cancer Research, Uppsala, Sweden.
    Demonstration of functionally different interactions between phospholipase C-gamma and the two types of platelet-derived growth factor receptors1995In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 270, no 13, p. 7773-7781Article in journal (Refereed)
    Abstract [en]

    Phosphorylated tyrosine residues in receptor tyrosine kinases serve as binding sites for signal transduction molecules. We have identified two autophosphorylation sites, Tyr-988 and Tyr-1018, in the platelet-derived growth factor (PDGF) alpha-receptor carboxyl-terminal tail, which are involved in binding of phospholipase C-gamma (PLC-gamma). The capacities of the Y988F and Y1018F mutant PDGF alpha-receptors, expressed in porcine aortic endothelial cells, to bind PLC-gamma are 60 and 5% of that of the wild-type receptor, respectively. Phosphorylated but not unphosphorylated peptides containing Tyr-1018 are able to compete with the intact receptor for binding to immobilized PLC-gamma SH2 domains; a phosphorylated Tyr-988 peptide competes 10 times less efficiently. The complex between PLC-gamma and the PDGF alpha-receptor is more stable than that of PLC-gamma and the PDGF beta-receptor. However, PDGF stimulation results in a smaller fraction of tyrosine-phosphorylated PLC-gamma and a smaller accumulation of inositol trisphosphate in cells expressing the alpha-receptor as compared with cells expressing the beta-receptor. We conclude that phosphorylated Tyr-988 and Tyr-1018 in the PDGF alpha-receptor carboxyl-terminal tail bind PLC-gamma, but this association leads to only a relatively low level of tyrosine phosphorylation and activation of PLC-gamma.

  • 5.
    Fagerström, Sofia
    et al.
    Department of Laboratory Medicine, Lund University, University Hospital MAS, Malmö.
    Påhlman, Sven
    Department of Laboratory Medicine, Lund University, University Hospital MAS, Malmö.
    Nånberg, Eewa
    Department of Pathology, University Hospital, Uppsala, Sweden.
    Protein kinase C-dependent tyrosine phosphorylation of p130cas in differentiating neuroblastoma cells1998In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 273, no 4, p. 2336-2343Article in journal (Refereed)
    Abstract [en]

    The cell signaling docking protein p130cas became tyrosine-phosphorylated in SH-SY5Y human neuroblastoma cells during induced differentiation with 12-O-tetradecanoylphorbol-13-acetate (TPA) and serum or a combination of basic fibroblast growth factor (bFGF) and insulin-like growth factor-I (IGF-I). The differentiating cells develop a neuronal phenotype with neurites and growth cones and sustained activation of protein kinase C (PKC) and pp60c-src. The TPA-induced p130cas phosphorylation increased within 5 min of stimulation and persisted for at least 4 days, whereas bFGF/IGF-I-induced p130cas phosphorylation was biphasic. However, the increase in tyrosine phosphorylation of p130cas was not restricted to differentiation inducing stimuli. The phosphorylation was blocked by the specific PKC inhibitor GF 109203X, and transient transfection with active PKC-epsilon induced p130cas tyrosine phosphorylation. pp60c-src, known to directly phosphorylate p130cas in other cell systems, was not activated after stimulation with TPA or bFGF/IGF-I for up to 30 min, and the initial p130cas phosphorylation was resistant to the Src family kinase inhibitor herbimycin A. However, in long term stimulated cells, herbimycin A blocked the induced phosphorylation of p130cas. Also, overexpression of src induced phosphorylation of p130cas. p130cas protein and phosphorylated p130cas were present in growth cones isolated from differentiated SH-SY5Y cells. Inhibition of PKC activity in differentiating cells with GF 109203X leads to a rapid retraction of growth cone filopodia, and p130cas phosphorylation decreased transiently (within minutes). Growth cones isolated from these cells were virtually devoid of phosphorylated p130cas. These data suggest a function for p130cas as a PKC downstream target in SH-SY5Y cells and possibly also in their growth cones.

  • 6.
    Hall, Diana
    et al.
    Department of Physiology, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
    Poussin, Carine
    Department of Physiology, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
    Velagapudi, Vidya R.
    VTT Technical Research Centre of Finland, Espoo, Finland.
    Empsen, Christophe
    Vrije Universiteit Brussel, Brussels, Belgium.
    Joffraud, Magali
    Department of Physiology, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
    Beckmann, Jacques S.
    Service and Department of Medical Genetics, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland.
    Geerts, Albert E.
    Vrije Universiteit Brussel, Brussels, Belgium.
    Ravussin, Yann
    Department of Physiology, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
    Ibberson, Mark
    Service and Department of Medical Genetics, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland; Vital-IT, Lausanne, Switzerland.
    Oresic, Matej
    Örebro University, School of Medical Sciences. VTT Technical Research Centre of Finland, Espoo, Finland.
    Thorens, Bernard
    Department of Physiology, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
    Peroxisomal and microsomal lipid pathways associated with resistance to hepatic steatosis and reduced pro-inflammatory state2010In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 285, no 40, p. 31011-31023Article in journal (Refereed)
    Abstract [en]

    Accumulation of fat in the liver increases the risk to develop fibrosis and cirrhosis and is associated with development of the metabolic syndrome. Here, to identify genes or gene pathways that may underlie the genetic susceptibility to fat accumulation in liver, we studied A/J and C57Bl/6 mice that are resistant and sensitive to diet-induced hepatosteatosis and obesity, respectively. We performed comparative transcriptomic and lipidomic analysis of the livers of both strains of mice fed a high fat diet for 2, 10, and 30 days. We found that resistance to steatosis in A/J mice was associated with the following: (i) a coordinated up-regulation of 10 genes controlling peroxisome biogenesis and β-oxidation; (ii) an increased expression of the elongase Elovl5 and desaturases Fads1 and Fads2. In agreement with these observations, peroxisomal β-oxidation was increased in livers of A/J mice, and lipidomic analysis showed increased concentrations of long chain fatty acid-containing triglycerides, arachidonic acid-containing lysophosphatidylcholine, and 2-arachidonylglycerol, a cannabinoid receptor agonist. We found that the anti-inflammatory CB2 receptor was the main hepatic cannabinoid receptor, which was highly expressed in Kupffer cells. We further found that A/J mice had a lower pro-inflammatory state as determined by lower plasma levels and IL-1β and granulocyte-CSF and reduced hepatic expression of their mRNAs, which were found only in Kupffer cells. This suggests that increased 2-arachidonylglycerol production may limit Kupffer cell activity. Collectively, our data suggest that genetic variations in the expression of peroxisomal β-oxidation genes and of genes controlling the production of an anti-inflammatory lipid may underlie the differential susceptibility to diet-induced hepatic steatosis and pro-inflammatory state.

  • 7. Jones, I.
    et al.
    Lindberg, C.
    Jakobsson, S.
    Hellqvist, A.
    Hellman, U.
    Borg, B.
    Olsson, Per-Erik
    Insitutionen för Molekylärbiologi, Umeå Universitet.
    Molecular cloning and characterization of spiggin: an androgen-regulated extraorganismal adhesive with structural similarities to von Willebrand Factor-related proteins2001In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 276, no 21, p. 17857-17863Article in journal (Refereed)
    Abstract [en]

    One of the most definitive examples of a vertebrate extraorganismal structural protein can be found in three-spined sticklebacks (Gasterosteus aculeatus). In the breeding male the kidney hypertrophies and synthesizes an adhesive protein called "spiggin," which is secreted into the urinary bladder from where it is employed as a structural thread for nest building. This paper describes the first molecular characterization of spiggin and demonstrates that this adhesive is a protein complex assembled from a potential of three distinct subunits (alpha, beta, and gamma). These subunits arise by alternative splicing, and 11-ketoandrogens induce their expression in stickleback kidneys. Analysis of the predicted amino acid sequence of each subunit reveals a modular organization whose structural elements display a similarity to the multimerization domains found within von Willebrand Factor-related proteins. These results implicate that spiggin utilizes a conserved multimerization mechanism for the formation of a viscous agglutinate from its constituent subunits in the urinary bladders of male sticklebacks. This novel extraorganismal structural protein is therefore ideally suited to its function as an adhesive thread.

  • 8.
    Nånberg, Eewa
    et al.
    Department of Pathology, University Hospital, Uppsala, Sweden.
    Westermark, Bengt
    Department of Pathology, University Hospital, Uppsala, Sweden.
    Platelet-derived growth factor increases the turnover of GTP/GDP on Ras in permeabilized fibroblasts1993In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 268, no 24, p. 18187-18194Article in journal (Refereed)
    Abstract [en]

    The potent mitogen platelet-derived growth factor (PDGF) induced a rapid increase in Ras.GTP in permeabilized human and murine fibroblasts. The effect was initiated by both PDGF-AA acting exclusively through PDGF alpha-receptors, and by PDGF-BB interacting with both alpha- and beta-type receptors. The dose-response curves suggest that both receptor types mediate the response. PDGF-dependent Ras activation, measured as increased formation of Ras.GTP, was rapid and reversible. At 37 degrees C the effect had a duration of around 10 min. The PDGF-dependent increase in Ras.GTP was followed by a simultaneous increase in Ras.GDP. Under no experimental condition could a relative increase in Ras.GTP be detected. 0.5 microM GDP and 0.5 microM GTP were equally potent competing for the formation of Ras.[alpha-32P]GTP upon PDGF stimulation. Furthermore, when the basal nucleotide exchange rate on Ras was elevated by omission of Mg2+ from the medium, PDGF had no further effect on the formation of Ras.GTP. We therefore conclude that PDGF activates Ras through a mechanism leading to an increased nucleotide exchange on Ras.

  • 9.
    Pradhan, Ajay
    et al.
    Örebro University, School of Science and Technology.
    Khalaf, Hazem
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden.
    Ochsner, Scott A.
    Baylor College of Medicine, Houston, USA.
    Sreenivasan, Rajini
    Temasek Life Sciences Laboratory, Singapore, Singapore.
    Koskinen, Jarno
    Örebro University, School of Science and Technology.
    Karlsson, Marie
    Örebro University, School of Science and Technology.
    Karlsson, Jesper
    Department of Biology, School of Science and Technology, Örebro University, Örebro, Sweden.
    McKenna, Neil J.
    Baylor College of Medicine, Houston, USA.
    Orban, Laszlo
    Temasek Life Sciences Laboratory, Singapore, Singapore; National University of Singapore, Singapore, Singapore; University of Pannonia, Keszthely, Hungary.
    Olsson, Per-Erik
    Örebro University, School of Science and Technology.
    Activation of NF-kappa B Protein Prevents the Transition from Juvenile Ovary to Testis and Promotes Ovarian Development in Zebrafish2012In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 287, no 45, p. 37926-37938Article in journal (Refereed)
    Abstract [en]

    Testis differentiation in zebrafish involves juvenile ovary to testis transformation initiated by an apoptotic wave. The molecular regulation of this transformation process is not fully understood. NF-kappa B is activated at an early stage of development and has been shown to interact with steroidogenic factor-1 in mammals, leading to the suppression of anti-Mullerian hormone (Amh) gene expression. Because steroidogenic factor-1 and Amh are important for proper testis development, NF-kappa B-mediated induction of anti-apoptotic genes could, therefore, also play a role in zebrafish gonad differentiation. The aim of this study was to examine the potential role of NF-kappa B in zebrafish gonad differentiation. Exposure of juvenile zebrafish to heat-killed Escherichia coli activated the NF-kappa B pathways and resulted in an increased ratio of females from 30 to 85%. Microarray and quantitative real-time-PCR analysis of gonads showed elevated expression of NF-kappa B-regulated genes. To confirm the involvement of NF-kappa B-induced anti-apoptotic effects, zebrafish were treated with sodium deoxycholate, a known inducer of NF-kappa B or NF-kappa B activation inhibitor (NAI). Sodium deoxycholate treatment mimicked the effect of heat-killed bacteria and resulted in an increased proportion of females from 25 to 45%, whereas the inhibition of NF-kappa B using NAI resulted in a decrease in females from 45 to 20%. This study provides proof for an essential role of NF-kappa B in gonadal differentiation of zebrafish and represents an important step toward the complete understanding of the complicated process of sex differentiation in this species and possibly other cyprinid teleosts as well.

  • 10.
    Welinder, Karen Gjesing
    et al.
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark.
    Hansen, Rasmus
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark; Wellspring Biosciences LLC, San Diego CA, United States.
    Overgaard, Michael Toft
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark.
    Brohus, Malene
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark.
    Sønderkær, Mads
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark.
    von Bergen, Martin
    Department of Chemistry and Bioscience, Section of Biotechnology, Aalborg University, Aalborg, Denmark; Department of Metabolomics, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany; Department of Proteomics, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.
    Rolle-Kampczyk, Ulrike
    Department of Metabolomics, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.
    Otto, Wolfgang
    Department of Proteomics, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.
    Lindahl, Tomas L.
    Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
    Arinell, Karin
    Örebro University, School of Medical Sciences. Department of Cardiology, Örebro University Hospital, Örebro, Sweden.
    Evans, Alina L.
    Department of Forestry and Wildlife Management, Hedmark University College Evenstrand, Elverum, Norway.
    Swenson, Jon E.
    Department for Ecology and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway; Norwegian Institute for Nature Research, Trondheim, Norway.
    Revsbech, Inge G.
    Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark.
    Fröbert, Ole
    Department of Cardiology, Faculty of Health, Örebro University, Örebro, Sweden.
    Biochemical Foundations of Health and Energy Conservation in Hibernating Free-Ranging Subadult Brown Bear Ursus arctos2016In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, no 43, p. 22509-22523Article in journal (Refereed)
    Abstract [en]

    Brown bears (Ursus arctos) hibernate for 5-7 months without eating, drinking, urinating and defecating at a metabolic rate of only 25% of the summer activity rate. Nonetheless, they emerge healthy and alert in spring. We quantified the biochemical adaptations for hibernation by comparing the proteome, metabolome, and hematologic features of blood from hibernating and active free-ranging subadult brown bears with a focus on conservation of health and energy. We found that total plasma protein concentration increased during hibernation, even though the concentrations of most individual plasma proteins decreased, as did the white blood cell types. Strikingly, antimicrobial defense proteins increased in concentration. Central functions in hibernation involving the coagulation response and protease inhibition, as well as lipid transport and metabolism, were upheld by increased levels of very few key or broad-specificity proteins. The changes in coagulation factor levels matched the changes in activity measurements. A dramatic 45-fold increase in sex-hormone-binding-globulin SHBG levels during hibernation draws, for the first time, attention to its significant but unknown role in maintaining hibernation physiology. We propose that energy for the costly protein synthesis is reduced by three mechanisms, (i) dehydration, which increases protein concentration without de novo synthesis; (ii) reduced protein degradation rates due to a 6 °C reduction in body temperature, and decreased protease activity; and (iii) a marked redistribution of energy resources only increasing de novo synthesis of few key proteins. This comprehensive global data identified novel biochemical strategies for bear adaptations to the extreme condition of hibernation, and have implications for our understanding of physiology in general.

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