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Results for “Secretory Vesicles”

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At least 163 records · Page 9Linked to original sources

PubMed1985

Histochemical analysis of secretory vesicles in nongoblet conjunctival epithelial cells.

An Alcian-blue/Periodic acid Schiff reagent (AB/PAS) pH dependent staining method was used to identify the mucus content of secretory vesicles of non-goblet epithelial cells of the human conjunctiva. Twenty subjects were selected for biopsy of the midcentral upper tarsal conjunctiva: 10 subjects had no contact lens wearing experience, and 10 subjects wore contact lenses. Human respiratory epithelium was used as a control for the staining procedure. Four-micron paraffin sections of conjunctival and control tissues were stained with Alcian blue at pH 2.5 and 1.0 and counterstained with PAS. Non-goblet epithelial cell secretory vesicles contained neutral mucin, sialmucin, and sulphomucin. This study provides evidence for a 'second' mucus system of the conjunctiva, that this system is in the non-goblet epithelial cells, and that the mucus of this system has sulphomucins, sialomucins and neutral mucins.

Conjunctiva↗

PubMed1988

Pro-opiomelanocortin and pro-vasopressin converting enzyme in pituitary secretory vesicles.

Peptide hormones are synthesized from larger precursors by cleavages at paired basic residues. We have isolated a pro-hormone converting enzyme from bovine neural and intermediate lobe secretory vesicles that cleaves pro-vasopressin and pro-opiomelanocortin at Lys-Arg residues to yield vasopressin, and adrenocorticotropin/endorphin-related peptides, respectively. The enzyme from both lobes is an aspartyl protease of approximately 70,000 Da, is a glycoprotein and has an optimum pH range of 4.0-5.0. Present within the same secretory vesicles is an aminopeptidase B-like enzyme which is a metalloprotease that is inhibited by Co2+ and Zn2+. This enzyme may play a role in trimming off the N-terminal extended basic residues from peptides liberated by the pro-hormone converting enzyme.

Animals↗

PubMed1998

Submaximal responses in calcium-triggered exocytosis are explained by differences in the calcium sensitivity of individual secretory vesicles.

A graded response to calcium is the defining feature of calcium-regulated exocytosis. That is, there exist calcium concentrations that elicit submaximal exocytotic responses in which only a fraction of the available population of secretory vesicles fuse. The role of calcium-dependent inactivation in defining the calcium sensitivity of sea urchin egg secretory vesicle exocytosis in vitro was examined. The cessation of fusion in the continued presence of calcium was not due to calcium-dependent inactivation. Rather, the calcium sensitivity of individual vesicles within a population of exocytotic vesicles is heterogeneous. Any specific calcium concentration above threshold triggered subpopulations of vesicles to fuse and the size of the subpopulations was dependent upon the magnitude of the calcium stimulus. The existence of multiple, stable subpopulations of vesicles is consistent with a fusion process that requires the action of an even greater number of calcium ions than the numbers suggested by models based on the assumption of a homogeneous vesicle population.

Animals↗

PubMed2004

Syncollin inhibits regulated corticotropin secretion from AtT-20 cells through a reduction in the secretory vesicle population.

Syncollin is a 13 kDa protein that is highly expressed in the exocrine pancreas. Syncollin normally exists as a doughnut-shaped homo-oligomer (quite probably a hexamer) in close association with the luminal surface of the zymogen granule membrane. In the present study, we examine the effect of expression of syncollin in AtT-20 neuroendocrine cells, which do not normally express this protein. Efficient expression was achieved by infection of the cells with adenoviral constructs encoding either untagged or GFP (green fluorescent protein)-tagged syncollin. Both forms of the protein were sorted into corticotropin (ACTH)-positive secretory vesicles present mainly at the tips of cell processes. Neither form affected basal corticotropin secretion or the constitutive secretion of exogenously expressed secreted alkaline phosphatase. In contrast, regulated secretion of corticotropin was inhibited (by 49%) by untagged but not by GFP-tagged syncollin. In parallel, untagged syncollin caused a 46% reduction in the number of secretory vesicles present at the tips of the cell processes. Syncollin-GFP was without effect. We could also show that native syncollin purified from rat pancreas was capable of permeabilizing erythrocytes. We suggest that syncollin may induce uncontrolled permeabilization of corticotropin-containing vesicles and subsequently destabilize them. Both forms of syncollin were tightly membrane-associated and appeared to exist as homooligomers. Hence, the lack of effect of syncollin-GFP on regulated exocytosis suggests that the GFP tag interferes in a subtler manner with the properties of the assembled protein.

Adrenocorticotropic Hormone↗

PubMed2003

[Use of three-dimensional fluorescence deconvolution microscopy for study of spatial distribution of secretory vesicles in living cells].

A three-dimensional image of a living cell is helpful for cell secretion study. In this report, the three-dimensional fluorescence deconvolution microscopy for observing living cells was studied, because this technique can obtain a quick three-dimensional imaging with minimal fluorescence quenching and cytotoxicity for living cell observation. The property of three-dimensional point spread function (PSF) of imaging system was analyzed. The relationship between experimental and theoretical PSF was illustrated, and the theoretical PSF was proved that it could reflect the principle of imaging system with NA 1.65 objective in use. Three-dimensional deconvolution algorithm in this report was proved effective by well-defined three-dimensional specimens. Furthermore, the rat pancreatic beta cell secretory vesicles labeled by acridine orange was observed by using this technique. Results showed that the blurring induced by out-of-focus light was removed by the deconvolution algorithm effectively, under current experiment conditions (with NA 1.65 objective) the experimental PSF approximated the theoretical PSF very well, and deconvolved living cell images exhibited the spatial distribution of the secretory vesicles clearly.

Algorithms↗

PubMed1999

Chitinase secretion by encysting Entamoeba invadens and transfected Entamoeba histolytica trophozoites: localization of secretory vesicles, endoplasmic reticulum, and Golgi apparatus.

Entamoeba histolytica, the protozoan parasite that phagocytoses bacteria and host cells, has a vesicle/vacuole-filled cytosol like that of macrophages. In contrast, the infectious cyst form has four nuclei and a chitin wall. Here, anti-chitinase antibodies identified hundreds of small secretory vesicles in encysting E. invadens parasites and in E. histolytica trophozoites overexpressing chitinase under an actin gene promoter. Abundant small secretory vesicles were also identified with antibodies to the surface antigen Ariel and with a fluorescent substrate of cysteine proteinases. Removal of an N-terminal signal sequence directed chitinase to the cytosol. Addition of a C-terminal KDEL peptide, identified on amebic BiP, retained chitinase in a putative endoplasmic reticulum, which was composed of a few vesicles of mixed sizes. A putative Golgi apparatus, which was Brefeldin A sensitive and composed of a few large, perinuclear vesicles, was identified with antibodies to ADP-ribosylating factor and to epsilon-COP. We conclude that the amebic secretory pathway is similar to those of other eukaryotic cells, even if its appearance is somewhat different.

ADP-Ribosylation Factors↗

PubMed2002

Nerve growth factor enhances neurotransmitter release from PC12 cells by increasing Ca(2+)-responsible secretory vesicles through the activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase.

Neurotrophins play important roles in the differentiation and survival of neurons during development, and in the regulation of synaptic transmission in adult brain. Brief treatment with nerve growth factor (NGF) enhances depolarization and ionomycin-induced dopamine and acetylcholine release from PC12 cells. The enhancing effect appears very quickly and reaches a plateau 10-15 min after application. NGF also enhances hypertonic solution-induced dopamine release, and increases the amount of dopamine released from membrane-permeabilized PC12 cells in the absence of MgATP, suggesting that NGF enhances neurotransmitter release by increasing the number of Ca(2+)-responsive secretory vesicles. The activation of Trk receptors is essential for NGF action, since K252a abolishes the NGF-induced potentiation of dopamine release and brain-derived neurotrophic factor enhanced ionomycin-induced release only in TrkB-expressing cells. NGF-mediated potentiation of dopamine release is completely abolished by wortmannin, a PI 3-kinase inhibitor, and by U0126 and PD98059, MAP kinase kinase inhibitors, indicating that the activation of PI 3-kinase and MAP kinase pathways is essential for NGF action. These findings suggest that NGF regulates neurotransmitter release through the activation of TrkA receptors, possibly by increasing the number of secretory vesicles in a readily releasable pool.

Animals↗

PubMed1987

The androgen-dependent mouse seminal vesicle secretory protein IV: characterization and complementary deoxyribonucleic acid cloning.

Seminal vesicle secretory protein IV of a mouse has been isolated, and the cDNA coding for its mRNA has been cloned and sequenced. The 556-nucleotides encode 16 amino acid signal peptides and 92 residues of mature protein. Considerable homology between mouse and rat SVS IV cDNA was found. In the leader peptide and 3'-noncoding region there is 92% and 85% homology, respectively. The other regional homologies are 86% for the first 12, 68.5% for the last 35, and 40% for the middle 44 amino acids. The expression of mouse SVS IV mRNA is under the control of androgen. Administration of testosterone to castrated mice resulted in induction of the mRNA level to 50% of the mature male in 96 h of hormone treatment. Secretion of the protein after testosterone injection follows a similar pattern.

Amino Acid Sequence↗

PubMed1994

pH-dependent interaction of chromogranin A with integral membrane proteins of secretory vesicle including 260-kDa protein reactive to inositol 1,4,5-triphosphate receptor antibody.

Chromogranin A is a high capacity, low affinity Ca(2+)-binding protein suggested to be responsible for the Ca2+ storage function of the secretory vesicle, which has been identified as a major inositol 1,4,5-trisphosphate (IP3)-sensitive intracellular Ca2+ store of adrenal medullary chromaffin cells. Moreover, chromogranin A has recently been shown to interact with the vesicle membrane at the intravesicular pH of 5.5 and to be released from it at a near physiological pH of 7.5 (Yoo, S. H. (1993) Biochemistry 32, 8213-8219). In the present study, chromogranin A is shown to interact with several integral membrane proteins of secretory vesicles at pH 5.5 but not at pH 7.5. One of the chromogranin A-interacting membrane proteins had a mass of 260 kDa and reacted with the IP3 receptor antibody. This result suggested not only the existence of the IP3 receptor in the vesicle membrane but also the existence of direct communication between chromogranin A and the IP3 receptor. In addition, the pH-dependent interaction of chromogranin A with integral membrane proteins implies an important role for chromogranin A in the sorting process of the vesicle membrane proteins during vesicle biogenesis in the trans-Golgi network.

Adrenal Medulla↗

PubMed1983

Characterization of a genomic clone for rat seminal vesicle secretory protein IV.

The entire coding region for rat seminal vesicle secretory protein IV was obtained on a 3.5 kb Eco RI fragment isolated from a genomic library in lambda Charon 4A. The coding sequence for SVS IV message is interrupted twice by introns. The first lies just downstream from the juncture of the 21 amino acid secretory signal peptide with the start of the mature protein, and the second lies in the 3'-nontranslated region. The major transcriptional start site was mapped by primer extention and is 22 nucleotides upstream from the translational initiation codon. S1 protection experiments indicated additional minor transcriptional starts about 27 and 50 nucleotides further upstream from the major cap site. The entire transcriptional unit comprises about 1740 nucleotides. The SVS IV gene does not belong to an obvious gene family, and it is conserved in mice and guinea pigs.

Amino Acid Sequence↗

PubMed1986

Purification and characterization of a paired basic residue-specific prohormone-converting enzyme from bovine pituitary neural lobe secretory vesicles.

The neuropeptides arginine vasopressin and oxytocin are generated from their prohormones in the hypothalamoneurohypophysial system by enzymatic cleavages at paired basic residues (i.e. Lys-Arg). This study describes the purification of an enzyme from bovine neural lobe secretory vesicles, the putative site of this processing, which is capable of cleaving several prohormones at paired basic residues. The enzyme is a glycoprotein of Mr approximately 70,000 and has an acidic pH maximum. It processes the heterologous precursors pro-opiomelanocortin and insulin at paired basic residues in a manner similar to a pro-opiomelanocortin-converting enzyme derived from bovine intermediate lobe secretory vesicles which has been described previously. In addition, the neural lobe-derived converting enzyme cleaves the human vasopressin prohormone in vitro to yield arginine vasopressin-Gly10-Lys11-Arg12 as the major vasopressin cleavage product. This indicates that the enzymatic cleavage in the vasopressin precursor occurred primarily on the carboxyl side of the arginine in the pair of Lys-Arg basic residues separating the vasopressin peptide from the neurophysin moiety in the precursor. The properties of the neural and intermediate lobe-derived enzymes are virtually identical, raising the possibility that a family of similar enzymes may be responsible for cleaving a number of prohormones at paired basic residues in different tissues.

Animals↗

PubMed1989

The secretory vesicle in living Paramecium is acidic.

In Paramecium, secretory proteins are packaged within membrane-bounded vesicles in a condensed form. This form expands when the proteins are released. We have now determined that a proton gradient is present in the secretory vesicles of living Paramecium. Acridine Orange, used as an in vivo indicator of acidic compartments, stained the secretory vesicles in both wild-type and mutant cells. Addition of the two agents that dissipate proton gradients (protonophores), namely, 2,4-dinitrophenol (DNP) and carbonylcyanide m-chlorophenylhydrazone (CCCP), eliminated this staining. Washed cells re-established their intravesicular acidity. Effects of sodium azide on vesicular acidity suggest that proton transport in these vesicles involves an ATP-dependent mechanism.

Acridine Orange↗

PubMed2001

The yeast Rvs161 and Rvs167 proteins are involved in secretory vesicles targeting the plasma membrane and in cell integrity.

The Rvs161 and Rvs167 proteins are known to play a role in actin cytokeleton organization and endocytosis. Moreover, Rvs167p functionally interacts with the myosin Myo2p. Therefore, we explored the involvement of the Rvs proteins in vesicle traffic and in cell integrity. The rvs mutants accumulate late secretory vesicles at sites of membrane and cell wall construction. They are synthetic-lethal with the slt2/mpk1 mutation, which affects the MAP kinase cascade controlled by Pkc1p and is required for cell integrity. The phenotype of the double mutants is close to that described for the pkc1 mutant. Synthetic defects for growth are also observed with mutation in KRE6, a gene coding for a glucan synthase, required for cell wall construction. These data support the idea that the Rvs proteins are involved in the late targeting of vesicles whose cargoes are required for cell wall construction.

Cell Membrane↗

PubMed1994

Neutrophil control of formylmethionyl-leucyl-phenylalanine induced mobilization of secretory vesicles and NADPH-oxidase activation: effect of an association of the ligand-receptor complex to the cytoskeleton.

The stimulus formylmethionyl-leucyl-phenylalanine (FMLP) interacts with neutrophils and generates signal(s) in the cells that induces mobilization of the secretory vesicles as well as activation of the superoxide anion/hydrogen peroxide generating NADPH-oxidase. Binding, at 15 degrees C, of FMLP to its neutrophil surface receptor is followed by an association of the ligand-receptor complex to the cell cytoskeleton, and this association occurs concomitant with a desensitization of the cells with respect to activation of the NADPH-oxidase. Other stimuli can still activate the oxidase (in fact even induce a primed response), indicating that the observed phenomenon is stimulus specific and could not be accounted for by an effect on the oxidase itself, but rather that the association of the ligand-receptor complex to the cytoskeleton eliminates the capacity of the complex to generate the signal(s) that activates the NADPH-oxidase. The cytoskeleton associated ligand-receptor complex generates, however, the signal(s) responsible for mobilization of the secretory vesicles, to the plasma membrane, and this mobilization occurs without any increase in the intracellular concentration of free Ca2+.

Calcium↗

PubMed2003

Neutrophil granules and secretory vesicles in inflammation.

The neutrophil is a major effector cell of innate immunity. Exocytosis of granules and secretory vesicles plays a pivotal role in most neutrophil functions from early activation to the destruction of phagocytosed microorganisms. Neutrophil granules contain a multitude of antimicrobial and potentially cytotoxic substances that are delivered to the phagosome or to the exterior of the cell following degranulation. This review summarises current knowledge of granule biology and highlights the effects of neutrophil degranulation in the acute inflammatory response.

Cell Degranulation↗

PubMed1984

Morphometric evaluation of lipid droplet associations with secretory vesicles, mitochondria and other components in the lactating cell.

The size, cellular location, and identity of surface-associated components were determined for lipid droplets in lactating cells. Transmission electron-microscopic measurements were made involving 3801 droplets in approximately 211 cells from three rats and 1197 droplets in 66 cells from a mouse. For the purposes of droplet evaluation, cells were divided into seven locations ranging from basal to secreting positions. Droplets were also categorized with respect to contact with other droplets, basolateral plasma membrane, mitochondria, Golgi apparatus, secretory vesicles, and endoplasmic reticulum-cytoplasm (ERC). Data on droplet size showed that droplet growth occurs mainly in the secretory position, confirming previously published findings. Lipid droplets from mouse tissue, although somewhat smaller in size showed similar growth trends to those of the rat. Data on numbers of droplet contacts and percentages of droplet circumferences involved in associations with other cell components showed that the dominant interaction of lipid droplets was with the ERC. However, intimate association of droplets with mitochondria was noted in all cellular locations. In addition, nursed animals exhibited a greater proportion of droplet surface association with secretory vesicles and less in contact with mitochondria in comparison to those not nursed. The significance of these relationships to milk synthesis and secretion is discussed.

Animals↗

PubMed1998

Non-opioid dynorphin binding site on secretory vesicles of a pituitary-derived cell line.

Accumulating evidence indicates that the endogenous opioid peptides dynorphinA-(1-17) and dynorphinA-(1-13) interact not only with opioid but also with yet poorly characterized non-opioid receptors. The latter have been implicated in a number of the effects of dynorphins including induction of ACTH release in sheep and in AtT 20 cells, a pituitary-derived mouse cell line. AtT 20 cells do not express opioid receptors and therefore are particularly suitable for search of non-opioid dynorphin receptors. We report here that 3H-dynorphinA-(1-13)-NH2 associates specifically with AtT 20 cells, apparently through an uptake process and a binding site. Within the cell, it binds preferentially to fractions containing secretory vesicles, with a Kd of about 100 nM. DynorphinA-(1-17), and several non-opioid fragments of dynorphin, including A-(2-17), A-(2-16) and A-(2-13), compete with 3H-dynorphinA-(1-13)-NH2 for that site with IC50s ranging from 200 nM to 2 microM. ACTH(1-39) also competes with 3H-dynorphinA-(1-13)-NH2 for the site with an IC50 of about 300 nM. DynorphinA-(2-17) at microM concentrations stimulates release of ACTH from the isolated vesicles. The results indicate the presence of a non-opioid dynorphin binding site on the secretory vesicle fractions of AtT20 cells that might be involved in ACTH release. The ability of ACTH itself to compete for the binding sites associated with the vesicles suggest that those sites may be involved in an autocrine loop.

Adrenocorticotropic Hormone↗

PubMed1983

3',5'-cyclic adenosine monophosphate- and Ca2+-calmodulin-dependent endogenous protein phosphorylation activity in membranes of the bovine chromaffin secretory vesicles: identification of two phosphorylated components as tyrosine hydroxylase and protein kinase regulatory subunit type II.

Membranes of the secretory vesicles from bovine adrenal medulla were investigated for the presence of the endogenous protein phosphorylation activity. Seven phosphoprotein bands in the molecular weight range of 250,000 to 30,000 were observed by means of the sodium dodecyl sulphate electrophoresis and autoradiography. On the basis of the criteria of molecular weight, selective stimulation of the phosphorylation by cyclic AMP (as compared with cyclic GMP) and immunoprecipitation by specific antibodies, band 5 (molecular weight 60,300) was found to represent the phosphorylated form of the secretory vesicle-bound tyrosine hydroxylase. The electrophoretic mobility, the stimulatory and inhibitory effects of cyclic AMP in presence of Mg2+ and Zn,2+ respectively, and immunoreactivity toward antibodies showed band 6 to contain two forms of the regulatory subunits of the type II cyclic AMP-dependent protein kinase, distinguishable by their molecular weights (56,000 and 52,000, respectively). Phosphorylation of band 7 (molecular weight 29,800) was stimulated about 2 to 3 times by Ca2+ and calmodulin in the concentration range of both agents believed to occur in the secretory tissues under physiological conditions.

Adrenal Medulla↗