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101.
Capell A Kaether C Edbauer D Shirotani K Merkl S Steiner H Haass C 《The Journal of biological chemistry》2003,278(52):52519-52523
Two secretases are involved in the generation of amyloid beta-peptide, the principal component of amyloid plaques in the brains of Alzheimer's disease patients. While beta-secretase is a classical aspartyl protease, gamma-secretase activity is associated with a high molecular weight complex. One of the complex components, which is critically required for gamma-secretase activity is nicastrin (NCT). Here we investigate the assembly of NCT into the gamma-secretase complex. NCT mutants either lacking the entire cytoplasmic tail, the cytoplasmic tail, and the transmembrane domain (TMD), or containing a set of heterologous TMDs were expressed in cells with strongly reduced levels of endogenous NCT. Maturation of exogenous NCT, gamma-secretase complex formation and proteolytic function was then investigated. This revealed that the cytoplasmic tail of NCT is dispensable for gamma-secretase complex assembly and function. In contrast, the authentic TMD of NCT is critically required for the interaction with gamma-secretase complex components and for formation of an active gamma-secretase complex. Neither soluble NCT lacking any membrane anchor nor NCT containing a heterologous TMD were inserted into the gamma-secretase complex. We identified the N-terminal region of the NCT TMD as a functionally important entity of NCT. These data thus demonstrate that NCT interacts with other gamma-secretase complex components via its TMD. 相似文献
102.
Regulation of the interleukin-1 receptor antagonist in THP-1 cells by ligands of the peroxisome proliferator-activated receptor gamma 总被引:5,自引:0,他引:5
Monocytes/macrophages (Mphi) play a pivotal role in the persistence of chronic inflammation and local tissue destruction in diseases such as rheumatoid arthritis and atherosclerosis. The production by Mphi of cytokines, chemokines, metalloproteinases and their inhibitors is an essential component in this process, which is tightly regulated by multiple factors. The peroxisome proliferator-activated receptors (PPARs) were shown to be involved in modulating inflammation. PPARgamma is activated by a wide variety of ligands such as fatty acids, the anti-diabetic thiazolidinediones (TZDs), and also by certain prostaglandins of which 15-deoxy-Delta(12,14)-PGJ2 (PGJ2). High concentrations of PPARgamma ligands were shown to have anti-inflammatory activities by inhibiting the secretion of interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNFalpha) by stimulated monocytes.The aim of this study was to determine whether PGJ2 and TZDs would also exert an immunomodulatory action through the up-regulation of anti-inflammatory cytokines such as the IL-1 receptor antagonist (IL-1Ra). THP-1 monocytic cells were stimulated with PMA, thereby enhancing the secretion of IL-1, IL-6, TNFalpha, IL-1Ra and metalloproteinases. Addition of PGJ2 had an inhibitory effect on IL-1, IL-6 and TNFalpha secretion, while increasing IL-1Ra production. In contrast, the bona fide PPARgamma ligands (TZDs; rosiglitazone, pioglitazone and troglitazone) barely inhibited proinflammatory cytokines, but strongly enhanced the production of IL-1Ra from PMA-stimulated THP-1 cells. Unstimulated cells did not respond to TZDs in terms of IL-1Ra production, suggesting that in order to be effective, PPAR ligands depend on PMA signalling. Basal levels of PPARgamma are barely detectable in unstimulated THP-1 cells, while stimulation with PMA up-regulates its expression, suggesting that higher levels of PPARgamma expression are necessary for receptor ligand effects to occur. In conclusion, we demonstrate for the first time that TZDs may exert an anti-inflammatory activity by inducing the production of the IL-1Ra. 相似文献
103.
Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis 总被引:1,自引:0,他引:1
Griesbeck C Schütz M Schödl T Bathe S Nausch L Mederer N Vielreicher M Hauska G 《Biochemistry》2002,41(39):11552-11565
Biological sulfide oxidation is a reaction occurring in all three domains of life. One enzyme responsible for this reaction in many bacteria has been identified as sulfide:quinone oxidoreductase (SQR). The enzyme from Rhodobacter capsulatus is a peripherally membrane-bound flavoprotein with a molecular mass of approximately 48 kDa, presumably acting as a homodimer. In this work, SQR from Rb. capsulatus has been modified with an N-terminal His tag and heterologously expressed in and purified from Escherichia coli. Three cysteine residues have been shown to be essential for the reductive half-reaction by site-directed mutagenesis. The catalytic activity has been nearly completely abolished after mutation of each of the cysteines to serine. A decrease in fluorescence on reduction by sulfide as observed for the wild-type enzyme has not been observed for any of the mutated enzymes. Mutation of a conserved valine residue to aspartate within the third flavin-binding domain led to a drastically reduced substrate affinity, for both sulfide and quinone. Two conserved histidine residues have been mutated individually to alanine. Both of the resulting enzymes exhibited a shift in the pH dependence of the SQR reaction. Polysulfide has been identified as a primary reaction product using spectroscopic and chromatographic methods. On the basis of these data, reaction mechanisms for sulfide-dependent reduction and quinone-dependent oxidation of the enzyme and for the formation of polysulfide are proposed. 相似文献
104.
Overcoming the Thermal Instability of Efficient Polymer Solar Cells by Employing Novel Fullerene‐Based Acceptors 下载免费PDF全文
105.
106.
Brigitte Jeschke Kerstin Uhl Bernd Weist Dirk Schröder Thomas Meitinger Christoph Döhlemann H.-P. Vosberg 《Human genetics》1998,102(3):299-304
Hypertrophic cardiomyopathy (HCM) is a genetically and clinically heterogeneous myocardial disease that is in most cases
familial and transmitted in a dominant fashion. The most frequently affected gene codes for the cardiac (ventricular) β-myosin
heavy chain. We have investigated the genetic cause of an isolated case of HCM, which was marked by an extremely severe phenotype
and a very early age of onset. HCM is normally not a disease of small children. The proband was a boy who had suffered cardiac
arrest at the age of 6.5years (resuscitation by cardioconversion). Upon screening of the β-myosin heavy chain gene as a candidate,
two missense mutations, one in exon19 (Arg719Trp) and a second in exon12 (Met349Thr), were identified. The Arg719Trp mutation
was de novo, as it was not found in the parents. In contrast, the Met349Thr mutation was inherited through the maternal grandmother.
Six family members were carriers of this mutation but only the proband was clinically affected. Segregation and molecular
analysis allowed us to assign the Met349Thr mutation to the maternal and the Arg719Trp de novo mutation to the paternal β-myosin
allele. Thus, the patient has no normal myosin. We interpret these findings in terms of compound heterozygosity of a dominant
(Arg719Trp) and a recessive (Met349Thr) mutation. Whereas a single mutated Arg719Trp allele would be sufficient to cause HCM,
the concurrent Met349Thr mutation alone does not apparently induce the disease. Nevertheless, it conceivably contributes to
the particularly severe phenotype.
Received: 15 September 1997 / Accepted: 26 November 1997 相似文献
107.
108.
Alexis Jourdain Mariusz Karbowski Yves Mattenberger Sébastien Herzig Pascaline Clerc Ines Raschke Carsten Merkwirth Sarah Ehses Frank Krause David C Chan Christiane Alexander Christoph Bauer Richard Youle Thomas Langer Jean‐Claude Martinou 《The EMBO journal》2009,28(11):1589-1600
Mitochondria are dynamic organelles, the morphology of which results from an equilibrium between two opposing processes, fusion and fission. Mitochondrial fusion relies on dynamin‐related GTPases, the mitofusins (MFN1 and 2) in the outer mitochondrial membrane and OPA1 (optic atrophy 1) in the inner mitochondrial membrane. Apart from a role in the maintenance of mitochondrial DNA, little is known about the physiological role of mitochondrial fusion. Here we report that mitochondria hyperfuse and form a highly interconnected network in cells exposed to selective stresses. This process precedes mitochondrial fission when it is triggered by apoptotic stimuli such as UV irradiation or actinomycin D. Stress‐induced mitochondrial hyperfusion (SIMH) is independent of MFN2, BAX/BAK, and prohibitins, but requires L‐OPA1, MFN1, and the mitochondrial inner membrane protein SLP‐2. In the absence of SLP‐2, L‐OPA1 is lost and SIMH is prevented. SIMH is accompanied by increased mitochondrial ATP production and represents a novel adaptive pro‐survival response against stress. 相似文献
109.
Ganesan AN O'Rourke B Maack C Colecraft H Sidor A Johns DC 《Biochemical and biophysical research communications》2005,329(2):749-754
The alpha(1c) subunit of the cardiac L-type Ca(2+) channel, which contains the channel pore, voltage- and Ca(2+)-dependent gating structures, and drug binding sites, has been well studied in heterologous expression systems, but many aspects of L-type Ca(2+) channel behavior in intact cardiomyocytes remain poorly characterized. Here, we develop adenoviral constructs with E1, E3 and fiber gene deletions, to allow incorporation of full-length alpha(1c) gene cassettes into the adenovirus backbone. Wild-type (alpha(1c-wt)) and mutant (alpha(1c-D-)) Ca(2+) channel adenoviruses were constructed. The alpha(1c-D-) contained four point substitutions at amino acid residues known to be critical for dihydropyridine binding. Both alpha(1c-wt) and alpha(1c-D-) expressed robustly in A549 cells (peak L-type Ca(2+) current (I(CaL)) at 0 mV: alpha(1c-wt) -9.94+/-1.00pA/pF, n=9; alpha(1c-D-) -10.30pA/pF, n=12). I(CaL) carried by alpha(1c-D-) was markedly less sensitive to nitrendipine (IC(50) 17.1 microM) than alpha(1c-wt) (IC(50) 88 nM); a feature exploited to discriminate between engineered and native currents in transduced guinea-pig myocytes. 10 microM nitrendipine blocked only 51+/-5% (n=9) of I(CaL) in alpha(1c-D-)-expressing myocytes, in comparison to 86+/-8% (n=9) of I(CaL) in control myocytes. Moreover, in 20 microM nitrendipine, calcium transients could still be evoked in alpha(1c-D-)-transduced cells, but were largely blocked in control myocytes, indicating that the engineered channels were coupled to sarcoplasmic reticular Ca(2+) release. These alpha(1c) adenoviruses provide an unprecedented tool for structure-function studies of cardiac excitation-contraction coupling and L-type Ca(2+) channel regulation in the native myocyte background. 相似文献
110.
Christine Bernsmeier Anne C. Meyer-Gerspach Lea S. Blaser Lia Jeker Robert E. Steinert Markus H. Heim Christoph Beglinger 《PloS one》2014,9(1)