Search results for "Secretory"
showing 10 items of 150 documents
Automatic detection of large dense-core vesicles in secretory cells and statistical analysis of their intracellular distribution.
2010
Analyzing the morphological appearance and the spatial distribution of large dense-core vesicles (granules) in the cell cytoplasm is central to the understanding of regulated exocytosis. This paper is concerned with the automatic detection of granules and the statistical analysis of their spatial locations in different cell groups. We model the locations of granules of a given cell as a realization of a finite spatial point process and the point patterns associated with the cell groups as replicated point patterns of different spatial point processes. First, an algorithm to segment the granules using electron microscopy images is proposed. Second, the relative locations of the granules with…
Alpha- and gamma-interferon (IFNα, IFNγ) but not interleukin-1 (IL-1) modulate synthesis and secretion of β2-microglobulin by hepatocytes
1988
Soluble serum beta 2-microglobulin has been thought to result from membrane shedding by activated T-lymphocytes. This hypothesis could explain the increase of beta 2-microglobulin serum levels during virally induced mononucleosis, but not elevated levels as observed in other virally induced and in malignant diseases. In this paper we demonstrate that beta 2-microglobulin is a true secretory protein, and that its synthesis in hepatocytes is modulated by IFNs but not by IL-1. While the 45,000 MW HLA antigen can be found only in cell lysates, beta 2-microglobulin is shown to be secreted also into the culture medium like other secretory proteins (e.g. albumin-factor B-complement C3). Furthermor…
Organelle pH studies using targeted avidin and fluorescein–biotin
2000
Abstract Background: Mammalian organelles of the secretory pathway are of differing pH. The pH values form a decreasing gradient: the endoplasmic reticulum (ER) is nearly neutral, the Golgi is mildly acidic and the secretory granules are more acidic still (∼pH 5). The mechanisms that regulate pH in these organelles are still unknown. Results: Using a novel method, we tested whether differences in H + ‘leak' and/or counterion conductances contributed to the pH difference between two secretory pathway organelles. A pH-sensitive, membrane-permeable fluorescein–biotin was targeted to endoplasmic-reticulum- and Golgi-localized avidin-chimera proteins in HeLa cells. In live, intact cells, ER pH (…
ER-to-Golgi Transport: The COPII-Pathway
2006
The endoplasmic reticulum (ER) is the starting site of the journey of newly synthesized proteinsto the apoplast, plasma membrane and to the vacuolar compartments. Transport between these membranecompartments of the secretory pathway in eukaryotic cells is mediated by vesicles, which are producedby a budding mechanism involving coat proteins that capture specific cargo molecules and helppackage them into coated vesicles. These vesicles are known as COPII-coated vesicles, and are usuallyisolated after their induction in vitro using microsomal membranes, cytosol and a non-hydrolyzableGTP-analogue. COPII-coated vesicles are formed at specific sites in the ER known as ER-exit sites(ERES). ERES a…
The Chaperone Activity of Clusterin is Dependent on Glycosylation and Redox Environment
2014
Background/Aims: Clusterin (CLU), also known as Apolipoprotein J (ApoJ) is a highly glycosylated extracellular chaperone. In humans it is expressed from a broad spectrum of tissues and related to a plethora of physiological and pathophysiological processes, such as Alzheimer's disease, atherosclerosis and cancer. In its dominant form it is expressed as a secretory protein (secreted CLU, sCLU). During its maturation, the sCLU-precursor is N-glycosylated and cleaved into an α- and a β-chain, which are connected by five symmetrical disulfide bonds. Recently, it has been demonstrated that besides the predominant sCLU, rare intracellular CLU forms are expressed in stressed cells. Since these for…
Intestinal drug efflux: formulation and food effects
2001
The intestine, primarily regarded as an absorptive organ, is also prepared for the elimination of certain organic acids, bases and neutral compounds depending on their affinity to intestinal carrier systems. Several of the transport systems known to mediate efflux in the major clearing organs--liver and kidney--are also expressed in the intestine. Examples of secretory transporters in the intestine are P-glycoprotein, members of the multidrug resistance associated protein family, breast cancer resistance protein, organic cation transporters and members of the organic anion polypeptide family. In this communication, the P-glycoprotein mediated intestinal secretion of talinolol, a model compo…
Biosynthesis of ecdysones in isolated prothoracic glands and oenocytes of Tenebrio molitor in vitro.
1974
Abstract Isolated prothoracic glands from Tenebrio larvae synthesize in vitro α-ecdysone, but not β-ecdysone from 4-14C-cholesterol. Isolated abdominal oenocytes from the larvae synthesize mainly β-ecdysone, but only little α-ecdysone. When prothoracic glands and oenocytes are cultured together, the α-ecdysone derived from the prothoracic glands is oxidized by the oenocytes to β-ecdysone. The newly synthesized hormones are not stored in the cells, but are secreted into the medium if sufficient amounts of non-labelled hormones are present. If no unlabelled hormones are added to the culture medium, the newly formed hormones are converted to a large extent into polar conjugates.
3D-Ultrastructure, Functions and Stress Responses of Gastropod (Biomphalaria glabrata) Rhogocytes
2014
Rhogocytes are pore cells scattered among the connective tissue of different body parts of gastropods and other molluscs, with great variation in their number, shape and size. They are enveloped by a lamina of extracellular matrix. Their most characteristic feature is the "slit apparatus", local invaginations of the plasma membrane bridged by cytoplasmic bars, forming slits of ca. 20 nm width. A slit diaphragm creates a molecular sieve with permeation holes of 20×20 nm. In blue-blooded gastropods, rhogocytes synthesize and secrete the respiratory protein hemocyanin, and it has been proposed-though not proven-that in the rare red-blooded snail species they might synthesize and secrete the he…
Cholesterol binds to synaptophysin and is required for biogenesis of synaptic vesicles.
1999
Here, to study lipid-protein interactions that contribute to the biogenesis of regulated secretory vesicles, we have developed new approaches by which to label proteins in vivo, using photoactivatable cholesterol and glycerophospholipids. We identify synaptophysin as a major specifically cholesterol-binding protein in PC12 cells and brain synaptic vesicles. Limited cholesterol depletion, which has little effect on total endocytic activity, blocks the biogenesis of synaptic-like microvesicles (SLMVs) from the plasma membrane. We propose that specific interactions between cholesterol and SLMV membrane proteins, such as synaptophysin, contribute to both the segregation of SLMV membrane constit…
Sorting of a secretory protein (gp80) to the apical surface of Caco-2 cells
1994
We have investigated the synthesis and polarized secretion of the exogenous gp80 glycoprotein complex in the human epithelial adenocarcinoma cell line, Caco-2. gp80 is secreted at the apical surface of Madin-Darby canine kidney (MDCK) cells and should, therefore, display the signal(s) required for sorting into the apical exocytic pathway. In Caco-2 cells, no bona fide secretory protein released preferentially at the apical surface has been described so far. To address the question of whether Caco-2 cells possess a machinery capable of delivery of secretory proteins at the apical surface, we stably transfected the cells with a recombinant gene coding for the gp80 glycoprotein complex. Pulse-…