scholarly journals Selective nucleotide-release from dense-core granules in insulin-secreting cells

2005 ◽  
Vol 118 (18) ◽  
pp. 4271-4282 ◽  
Author(s):  
S. Obermuller
Keyword(s):  
Dense Core ◽  
Nucleotide Release ◽  
Insulin Secreting Cells ◽  
Dense Core Granules

Requirements for the identification of dense-core granules

2004 ◽  
Vol 14 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Jacopo Meldolesi ◽  
Evelina Chieregatti ◽  
Maria Luisa Malosio
Keyword(s):  
Dense Core ◽  
Dense Core Granules

scholarly journals Differential effects of G-protein activators on 5-hydroxytryptamine and platelet-derived growth factor release from streptolysin-O-permeabilized human platelets

1996 ◽  
Vol 314 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Philip J. PADFIELD ◽  
Ninder PANESAR ◽  
Patricia HENDERSON ◽  
Joseph J. BALDASSARE
Keyword(s):  
Growth Factor ◽  
G Protein ◽  
G Proteins ◽  
Protein S ◽  
Human Platelets ◽  
Dense Core ◽  
Platelet Derived Growth Factor ◽  
Permeabilized Cells ◽  
Streptolysin O ◽  
Dense Core Granules

In this paper we have used streptolysin O (SLO)-permeabilized human platelets to examine the G-protein(s) that control Ca2+-independent secretion from α and dense-core granules. As shown for electropermeabilized platelets, Ca2+ alone stimulated a concentration-dependent increase in 5-hydroxytryptamine (5-HT) (dense-core-granule marker) and platelet-derived growth factor (PDGF) (α-granule marker) release from the SLO-permeabilized cells. The EC50 values for Ca2+-dependent 5-HT and PDGF release were 5 μM and 10 μM respectively. Guanosine 5´-[γ-thio]triphosphate (GTP[S]) (100 μM) stimulated Ca2+-independent release from both α and dense-core granules. In contrast, AlF4- had no effect on Ca2+-independent release from either α or dense-core granules. Neither GTP[S] nor AlF4- appeared to have a significant effect on Ca2+-dependent release from α and dense-core granules. GTP[S] can activate both heterotrimeric and low-molecular-mass G-proteins, whereas AlF4- activates only heterotrimeric G-proteins. Our results, therefore suggest that secretion in the human platelet is regulated by a small G-protein. Both GTP[S]- and Ca2+-dependent secretion were effected by extending the time between permeabilization with SLO and stimulation of secretion. GTP[S]-stimulated secretion from α and dense-core granules decreased rapidly after permeabilization. In contrast, Ca2+-dependent 5-HT and PDGF release ran down at a much lower rate. These observations indicate that GTP[S] and Ca2+ act through parallel pathways to stimulate secretion from SLO-permeabilized platelets.

scholarly journals Expression of Rab3D N135I Inhibits Regulated Secretion of ACTH in AtT-20 Cells

1998 ◽  
Vol 140 (2) ◽  
pp. 305-313 ◽  
Author(s):  
Giulia Baldini ◽  
Giovanna Baldini ◽  
Guangyi Wang ◽  
Mattew Weber ◽  
Marina Zweyer ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Membrane Trafficking ◽  
Hormone Secretion ◽  
Dense Core ◽  
Rab Proteins ◽  
Wild Type ◽  
Small Molecular Weight ◽  
Vesicular Traffic ◽  
Regulated Secretion ◽  
Dense Core Granules

Rab proteins are small molecular weight GTPases that control vesicular traffic in eucaryotic cells. A subset of Rab proteins, the Rab3 proteins are thought to play an important role in regulated exocytosis of vesicles. In transfected AtT-20 cells expressing wild-type Rab3D, we find that a fraction of the protein is associated with dense core granules. In the same cells, expression of a mutated isoform of Rab3D, Rab3D N135I, inhibits positioning of dense core granules near the plasma membrane, blocks regulated secretion of mature ACTH, and impairs association of Rab3A to membranes. Expression of Rab3D N135I does not change the levels of ACTH precursor or the efficiency with which the precursor is processed into ACTH hormone and packaged into dense core granules. We also find that cells expressing mutated Rab3D differentiate to the same extent as untransfected AtT-20 cells. We conclude that expression of Rab3D N135I specifically impairs late membrane trafficking events necessary for ACTH hormone secretion.

Molecular mechanisms of platelet exocytosis: role of SNAP-23 and syntaxin 2 in dense core granule release

Blood ◽  
2000 ◽  
Vol 95 (3) ◽  
pp. 921-929 ◽  
Author(s):  
Dong Chen ◽  
Audrey M. Bernstein ◽  
Paula P. Lemons ◽  
Sidney W. Whiteheart
Keyword(s):  
Molecular Mechanisms ◽  
Cell Types ◽  
Dominant Negative ◽  
Dense Core ◽  
Protein Receptors ◽  
Dense Core Granules ◽  
Platelet Exocytosis ◽  
Granule Release

To characterize the molecular mechanisms of platelet secretion, we focused on the calcium-induced exocytosis of dense core granules. Platelets contain several known t-SNAREs (soluble N-ethylmaleimide sensitive factor [NSF] attachment protein receptors) such as syntaxins 2, 4, and 7 and SNAP-23 (synaptosomal associated protein 23). By using an in vitro exocytosis assay, we have been able to assign roles for some of these t-SNAREs in dense core granule release. This calcium-induced secretion relies on the SNARE proteins because it is stimulated by the addition of recombinant -SNAP and inhibited by a dominant negative -SNAP–L294A mutant or by anti–-SNAP and anti-NSF antibodies. SNAP-23 antibodies and an inhibitory C-terminal SNAP-23 peptide both blocked dense core granule release, demonstrating a role for SNAP-23. Unlike other cell types, platelets contain a significant pool of soluble SNAP-23, which does not partition into Triton X-114. Of the anti-syntaxin antibodies tested, only anti–syntaxin 2 antibody inhibited dense core granule release. Immunoprecipitation studies showed that the 2 t-SNAREs syntaxin 2 and SNAP-23 do form a complex in vivo. These data clearly show that SNAPs, NSF, and specific t-SNAREs are used for dense core granule release; these data provide a greater understanding of regulated exocytosis in platelets.

Platelets from Munc18c heterozygous mice exhibit normal stimulus-induced release

2004 ◽  
Vol 92 (10) ◽  
pp. 829-837 ◽  
Author(s):  
Todd Schraw ◽  
Garland Crawford ◽  
Qiansheng Ren ◽  
Wangsun Choi ◽  
C. Debbie ◽  
...  
Keyword(s):  
Dense Core ◽  
Critical Aspect ◽  
Platelet Factor ◽  
Normal Morphology ◽  
Binding Partner ◽  
Molecular Machinery ◽  
Apparent Reduction ◽  
Dense Core Granules ◽  
Platelet Exocytosis ◽  
Platelet Secretion

SummaryA critical aspect of hemostasis is the release of clot-forming components from the three intra-platelet stores: dense core granules, α-granules and lysosomes. Exocytosis from these granules is mediated by soluble (SNAPs and NSF) and integralmembrane proteins (v- and t-SNAREs).Three SM (Sec1/Munc18) proteins are present in mouse platelets (Munc18a, 18b and 18c) and each potentially regulates exocytosis via modulation of their cognate syntaxin binding partner. To define the molecular machinery required for platelet exocytosis, we analyzed platelets from Munc18c heterozygous knockout mice. These platelets show a decrease in Munc18c but no apparent reduction in other secretory machinery components. No differences in the rates of aggregation or of secretion of [3H]-5HT (dense core granules), platelet factor 4 (α-granules), or hexosaminidase (lysosomes) were detected between platelets from Munc18c heterozygous knockout or wild-type mice. The platelets also show normal morphology. Contrary to a predicted requirement for Munc18c in platelet secretion, data reported here show that reducing Munc18c levels does not substantially alter platelet function. These data show that despite Munc18c’s role in platelet secretion, the lack of a secretion defect may be attributed to compensation by other Munc18 isoforms or that one allele is sufficient to maintain secretion under standard conditions.

TEM studies of primitive neuroectodermal tumors with neuronal and glial differentiation

1989 ◽  
Vol 47 ◽  
pp. 854-855
Author(s):  
Joseph M. Harb
Keyword(s):  
Glial Cells ◽  
Basal Lamina ◽  
Ultrastructural Level ◽  
Dense Core ◽  
Glial Differentiation ◽  
Small Series ◽  
First Case ◽  
Cytoplasmic Filaments ◽  
Divergent Differentiation ◽  
Dense Core Granules

The term primitive neuroectodermal tumor (PNET) was originally applied in 1973 by Hart and Earle to refer to a group of undifferentiated cerebral neoplasms in children. Since that report, few studies have utilized the transmission electron microscope (TEM) to establish the identity of the tumor cells and to clarify the propensity of the PNETs for pluripotential differentiation. Of particular interest are reports which suggest the possibility of simultaneous neuronal and glial differentiation within the same cell. It would be of significant interest to know if the propensity to divergent differentiation can be explained by a single population of neoplastic cells that have the potential to differentiate in multiple directions. We will present a small series of cases with ultrastructural evidence that some of the cells in the tumors express both neuronal and glial features.The first case is a primary cerebral neuroblastoma which was associated with a population of neoplastic glial cells. At the ultrastructural level neuroblast and glial cell populations were identified. We also recognized a population of cells which displayed a continuous basal lamina and rare, poorly developed junctional complexes. Of particular interest was yet another, smaller, population of cells which displayed both dense-core granules and microtubules typical of neuroblasts and abundant cytoplasmic filaments typical of glial cells (Figure 1). In two other cases, the astrocytic nature of the cells was confirmed at the ultrastructural level on the basis of prominent glial filaments in the cytoplasm. However, some of the astrocytes in one of the cases were invested partially by a distinct basal lamina (Figure 2), and there were dense-core granules in the cytoplasm (Figure 2, inset).

The nature of breast dense core granules: uranaffin reactivity

1987 ◽  
Vol 11 (11) ◽  
pp. 1149-1159 ◽  
Author(s):  
H.E. HOPKINSON ◽  
S. BATTERSBY ◽  
T.J. ANDERSON
Keyword(s):  
Dense Core ◽  
Dense Core Granules

scholarly journals Targeting of P-selectin to two regulated secretory organelles in PC12 cells.

1996 ◽  
Vol 134 (5) ◽  
pp. 1229-1240 ◽  
Author(s):  
J P Norcott ◽  
R Solari ◽  
D F Cutler
Keyword(s):  
Amino Acids ◽  
Pc12 Cells ◽  
Transient Expression ◽  
Subcellular Fractionation ◽  
Cytoplasmic Domain ◽  
Dense Core ◽  
The Other ◽  
Lysosomal Targeting ◽  
Dense Core Granules ◽  
Carboxy Terminal

Targeting of P-selectin to the regulated secretory organelles (RSOs) of phaeochromocytoma PC12 cells has been investigated. By expressing from cDNA a chimera composed of HRP and P-selectin, and then following HRP activity through subcellular fractionation, we have discovered that P-selectin contains signals that target HRP to the synaptic-like microvesicles (SLMV) as well as the dense-core granules (DCGs) of these cells. Mutagenesis of the chimera followed by transient expression in PC12 cells shows that at least two different sequences within the carboxy-terminal cytoplasmic tail of P-selectin are necessary, but that neither is sufficient for trafficking to the SLMV. One of these sequences is centred on the 10 amino acids of the membrane-proximal C1 exon that is also implicated in lysosomal targeting. The other sequence needed for trafficking to the SLMV includes the last four amino acids of the protein. The same series of mutations have a different effect on DCG targeting, showing that traffic to the two different RSOs depends on different features within the cytoplasmic domain of P-selectin.

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