The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform

Harvey B Pollard - One of the best experts on this subject based on the ideXlab platform.

  • enhancement by f actin of mgatp dependent dopamine uptake into isolated Chromaffin Granules
    Iubmb Life, 1996
    Co-Authors: Kyoji Morita, Stuart M. Tomares, Harvey B Pollard
    Abstract:

    Interaction of Chromaffin Granules with the microfilament network in the cytoplasmic space of adrenal medullary cells has been proposed, but the influence of Chromaffin granule-microfilament interaction on granule function has not yet been studied. In the present study, the effect of F-actin on dopamine uptake into isolated Chromaffin Granules was examined. The MgATP-dependent component of dopamine uptake was significantly enhanced by F-actin. In contrast, catecholamine efflux from the Granules was not significantly altered by F-actin under the conditions in which the enhancement of MgATP-dependent dopamine uptake was observed. These findings suggest that the interaction of Chromaffin Granules with the microfilament network results in the enhancement of MgATP-dependent dopamine uptake into the Granules, thus modulating the accumulation and storage of catecholamines in the adrenal medullary cell.

  • Enhancement by F‐actin of MgATP‐dependent dopamine uptake into isolated Chromaffin Granules
    Iubmb Life, 1996
    Co-Authors: Kyoji Morita, Stuart M. Tomares, Harvey B Pollard
    Abstract:

    Interaction of Chromaffin Granules with the microfilament network in the cytoplasmic space of adrenal medullary cells has been proposed, but the influence of Chromaffin granule-microfilament interaction on granule function has not yet been studied. In the present study, the effect of F-actin on dopamine uptake into isolated Chromaffin Granules was examined. The MgATP-dependent component of dopamine uptake was significantly enhanced by F-actin. In contrast, catecholamine efflux from the Granules was not significantly altered by F-actin under the conditions in which the enhancement of MgATP-dependent dopamine uptake was observed. These findings suggest that the interaction of Chromaffin Granules with the microfilament network results in the enhancement of MgATP-dependent dopamine uptake into the Granules, thus modulating the accumulation and storage of catecholamines in the adrenal medullary cell.

  • immunolocalization of synexin annexin vii in adrenal Chromaffin Granules and Chromaffin cells evidence for a dynamic role in the secretory process
    Cell and Tissue Research, 1992
    Co-Authors: Gemma A J Kuijpers, Harvey B Pollard
    Abstract:

    Synexin (annexin VII) is a Ca2+- and phospholid-binding protein which has been proposed to play a role in Ca2+-dependent membrane fusion processes. Using a monoclonal antibody against synexin, Mab 10E7, and immunogold, we carried out a semiquantitative localization study of synexin in bovine adrenal medullary Chromaffin Granules, and in resting and nicotine-stimulated adrenal Chromaffin cells. Isolated Chromaffin Granules contained very little synexin, whereas Chromaffin Granules aggregated with synexin (24 μg/mg) and Ca2+ (1 mM) clearly showed synexin-associated immunogold particles in the vicinity of the granule membrane (1.88 gold particles per granule profile). In isolated, cultured adrenal Chromaffin cells, synexin was present in the nucleus (5.5 particles/μm2) and in the cytosol (5.3 particles/μm2), but mainly around the granule membrane in the granular cell area (11.7 particles/μm2). During the active phase of cholinergically stimulated catecholamine secretion, the amount of synexin label was reduced by 33% in the nucleus, by 23% in the cytosol, and by 51% in the granule area. The plasma membrane contained a small amount of synexin, which did not significantly change upon stimulation of the cells. We conclude that synexin is involved in the secretory process in Chromaffin cells.

Vivian Hook - One of the best experts on this subject based on the ideXlab platform.

  • protein trafficking to Chromaffin Granules and proteolytic processing within regulated secretory vesicles of neuroendocrine Chromaffin cells
    Annals of the New York Academy of Sciences, 2002
    Co-Authors: Vivian Hook, Mariehelene Metzboutigue
    Abstract:

    : Proteolytic processing within secretory vesicles is required for the production and secretion of biologically active peptide neurotransmitters and hormones, known collectively as neuropeptides. This chapter addresses several new aspects of proteolysis in secretory vesicles, Chromaffin Granules, with respect to sorting proneuropeptides or prohormones into such regulated secretory vesicles that use specific prohormone sorting signals. Concomitant with prohormone sorting, evidence for the role of chromogranin A in secretory granule biogenesis is presented. Secretory vesicle function involves endogenous serpin protease inhibitors for the regulation of proteolysis. The novel serpins endopin 1 and endopin 2 possess high homology to a1-antichymotrypsin, yet they possess distinct target protease specificities. The serpins PAI-1 and neuroserpin are also localized to Chromaffin Granules. In addition, regulation of secretory vesicle function involves cytochrome b561 that regulates reducing equivalents to maintain the intravesicular redox state. These studies demonstrate multiple components as regulatory factors in the control of secretory vesicle function for the biosynthesis and secretion of neuropeptides and catecholamines.

  • Purification and characterization of a cathepsin D protease from bovine Chromaffin Granules
    Biochemistry, 1992
    Co-Authors: Timothy J. Krieger, Vivian Hook
    Abstract:

    Purification and potential tachykinin and enkephalin precursor cleaving enzymes from bovine Chromaffin Granules was undertaken using as substrates the model precursors 35 S-(Met)-β-preprotachykinin [ 35 S-(Met)-β-PPT] and 35 S-(Met)-preproenkephalin [ 35 S-(Met)-PPE]. Purification by concanavalin A-Sepharose, Sephacryl S200, and chromatofocusing resulted in a Chromaffin granule aspartyl protease (CGAP) that preferred the tachykinin over the enkephalin precursor

H. Winkler - One of the best experts on this subject based on the ideXlab platform.

  • immunological characterization of the endoproteases pc1 and pc2 in adrenal Chromaffin Granules and in the pituitary gland
    FEBS Letters, 1992
    Co-Authors: Rudolf Kirchmair, Andrea Laslop, Reiner Fischercolbrie, Patricia Gee, R Hogueangeletti, H. Winkler
    Abstract:

    Specific antisera against synthetic Fragments of the endoproteases, PC1 and PC2, were used to characterize these proteins. In one-dimensional immunoblots these antisera labelled components of 85 kDa for PC1 and of 70 kDa for PC2 in purified bovine Chromaffin Granules and anterior and posterior pituitary of ox and rat. In membranes of bovine Chromaffin Granules glycoprotein H was identified as the major PC2 immunoreactive spot. A major part of these endoproteases appeared membrane bound.

  • synaptin synaptophysin p65 and sv2 their presence in adrenal Chromaffin Granules and sympathetic large dense core vesicles
    Biochimica et Biophysica Acta, 1991
    Co-Authors: Thomas Schmidle, Reiner Fischercolbrie, R Weiler, Claire Desnos, Daniel Scherman, Erik Floor, H. Winkler
    Abstract:

    The subcellular distribution of three proteins of synaptic vesicles (synaptin/synaptophysin, p65 and SV2) was determined in bovine adrenal medulla and sympathetic nerve axons. In adrenals most p65 and SV2 is confined to Chromaffin Granules. Part of synaptin/synaptophysin is apparently also present in these organelles, but a considerable portion is found in a light vesicle which does not contain significant concentrations of typical markers of Chromaffin Granules (cytochrome b -561, dopamine β-hydroxylase or the amine carrier). An analogous finding was obtained for sympathetic axons. The large dense core vesicles contain most p65 and also SV2 but only a smaller portion of synaptin/synaptophysin. A lighter vesicle containing this latter antigen and some SV2 has also been found. These results establish that in adrenal medulla and sympathetic axons three typical antigens of synaptic vesicles are not restricted to light vesicles. Apparently, a varying part of these antigens is found in Chromaffin Granules and large dense core vesicles. On the other hand, the light vesicles do not contain significant concentrations of functional antigens of Chromaffin Granules. Thus, the biogenesis of small presynaptic vesicles which contain all three antigens as well as functional components like the amine carrier is likely to involve considerable membrane sorting.

David K Apps - One of the best experts on this subject based on the ideXlab platform.

  • membrane and soluble proteins of adrenal Chromaffin Granules
    Seminars in Cell & Developmental Biology, 1997
    Co-Authors: David K Apps
    Abstract:

    Abstract Bovine adrenal Chromaffin Granules are useful ‘model’ neurosecretory vesicles, particularly for biochemical studies. The granule matrix contains three major secretory proteins (chromogranin A and secretogranins I and II) together with peptides derived from them, and smaller amounts of neuropeptides (enkephalins and neuropeptide Y). Several different endo- and exo-proteinases are also present in both soluble and membrane-bound forms. The major membrane proteins are those involved in catecholamine biosynthesis (dopamine β-monooxygenase and cytochrome b561), active transport of granule components (vacuolar-type proton-translocating ATPase, and carriers for monoamines, nucleotides and small ions) and exocytosis (synaptotagmin, synaptobrevin and other proteins). In addition, the functions of a number of major granule membrane proteins remain unknown.

Tateo Daimon - One of the best experts on this subject based on the ideXlab platform.

  • Presence of laminin B chain-like protein in bovine and rat adrenal Chromaffin Granules.
    Journal of Biochemistry, 1994
    Co-Authors: Yukio Fujino, Tomoko Fujii, Tateo Daimon
    Abstract:

    The presence of a glycoprotein laminin in bovine adrenal Chromaffin Granules was examined by SDS-PAGE followed by immunoblotting. The two Chromaffin granule membrane fractions were obtained by linear sucrose gradient centrifugation followed by freezing and thawing and gel-filtration of the Chromaffin granule-rich fraction, respectively. The purity of the Granules in these fractions was examined by electron microscopy. These fractions contained laminin B chain-like immunoreactivity as a major immunoreactive component against anti-laminin. Laminin A chain-like immunoreactive protein was undetectable. The soluble fraction of the Chromaffin Granules contained no immunoreactive peptide. The presence of laminin-like immunoreactivity in the Chromaffin Granules was confirmed by immunocytochemical study. Laminin B chain-like immunoreactivity was also identified in the rat adrenal Chromaffin granule fraction. Laminin A chain was hardly detected, as in the case of bovine adrenals. Structure of laminin in Chromaffin Granules in bovine and rat adrenals may be different from that of mouse Englebrethe-Holm-Swarm sarcoma laminin. The functional significance of laminin B chain-like protein in the Granules is unknown at present.