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  • 1
    Electronic Resource
    Electronic Resource
    Ligation of the α2-macroglobulin signaling receptor on macrophages induces synthesis of platelet activating factor (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 61 (1996), S. 39-47 
    Details
    ISSN: 0730-2312
    Keywords: α2M ; PAF ; RBF ; PKC ; lyso-PAF acetyltransferase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding of receptor-recognized forms of α2-macroglobulin (α2M) to macrophage α2M signaling receptors increases inositol-1,4,5-triphosphate synthesis and induces Ca2+ mobilization. In this report, we demonstrate that ligation of the macrophage α2M signaling receptor is also associated with synthesis of platelet activating factor (PAF) by both the de novo and remodeling pathways. Both α2M-methylamine and a cloned and expressed 20-kDa receptor binding fragment (RBF) from rat α2M+, stimulated macrophage synthesis of PAF from [3H]acetate, [3H]methylcholine, and 1-O-[3H]alkyl lyso-PAF by two- to threefold. PAF levels reached a peak in 20 min after the cells were exposed to α2M-methylamine or RBF; they remained elevated for about 1 h after ligand addition to the cells. When [3H]methylcholine was the substrate, pertussis toxin did not block PAF synthesis, but the protein kinase C inhibitor staurosporin reduced synthesis by 65-70%. Cycloheximide completely abolished the increase in synthesis of PAF by macrophages exposed to α2M-methylamine. By contrast, when [3H]acetate was employed as a precursor, staurosporin or cycloheximide did not abolish the increase in PAF synthesis. These studies suggest that protein kinase C is necessary for the induction of the de novo pathway by α2M-methylamine. Both α2M-methylamine and RBF stimulated the activity of lyso-PAF acetyltransferase by about fourfold. Both ligands also stimulated the activity of PAF acetylhydrolase by about six- to sevenfold, indicating that ligation of the α2M signaling receptor also regulates the degradation of PAF. The ability of receptor-recognized forms of α2M to regulate levels of PAF suggests that α2M-proteinase complexes not only regulate macrophage function by activating intracellular signaling but also may indirectly regulate the function of other cells that cannot bind α2M-proteinase complexes. © 1996 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Chloroquine, quinine and quinidine inhibit calcium release from macrophage intracellular stores by blocking inositol 1,4,5-trisphosphate binding to its receptor (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 225-232 
    Details
    ISSN: 0730-2312
    Keywords: chemotherapy of malaria ; inositol trisphosphate receptors ; chloroquine ; cytosolic calcium ; endocytosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding of many ligands to cellular receptors induces a signaling cascade which generates inositol 1,4,5-trisphosphate (IP3). IP3 binding to its receptors in various internal compartments causes a rapid Ca2+ efflux into the cytosol. We now demonstrate that chloroquine blocks ligand-induced Ca2+ mobilization without affecting IP3 synthesis. The effect is independent of the ligand employed and occurred with five unrelated ligands; namely, α2-macroglobulin-methylamine, angiotensin II, bradykinin, carbachol, and epidermal growth factor. Chloroquine, quinidine, and quinine, however, block binding of [3H]IP3 to its receptors by 90%, 88%, and 71%, respectively. These observations suggest a previously undetected mechanism by which these agents may in part function as antimalarials. J. Cell. Biochem. 64:225-232. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
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