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.

scholarly journals Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules

2009 ◽  
Vol 8 (10) ◽  
pp. 1575-1583 ◽  
Author(s):  
Abdur Rahaman ◽  
Wei Miao ◽  
Aaron P. Turkewitz
Keyword(s):  
Tetrahymena Thermophila ◽  
Secretory Granules ◽  
Gel Filtration ◽  
Dense Core ◽  
Crystalline Lattice ◽  
Wild Type ◽  
Biochemical Component ◽  
Protein Classes ◽  
Dense Core Granules

ABSTRACT Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal β/γ-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, ΔGRT1 ΔGRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in ΔGRT1 ΔGRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from ΔGRT1 ΔGRT2 cells appear less adhesive than those from the wild type.

scholarly journals Maturation of dense core granules in wild type and mutant Tetrahymena thermophila.

1991 ◽  
Vol 10 (8) ◽  
pp. 1979-1987 ◽  
Author(s):  
A.P. Turkewitz ◽  
L. Madeddu ◽  
R.B. Kelly
Keyword(s):  
Tetrahymena Thermophila ◽  
Dense Core ◽  
Wild Type ◽  
Dense Core Granules

The Phosphoinositide Signal Transduction Pathway in the Pathogenesis of Alzheimer’s Disease

2018 ◽  
Vol 15 (4) ◽  
pp. 355-362 ◽  
Author(s):  
Vincenza Rita Lo Vasco
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Signal Transduction ◽  
Membrane Trafficking ◽  
Hormone Secretion ◽  
Signal Transduction Pathway ◽  
Brain Morphology ◽  
Signal Transduction Pathways ◽  
Transduction Pathway ◽  
Cell Functions

Background: During aging and in age-associated disorders, such as Alzheimer's Disease (AD), learning abilities decline. Probably, disturbances in signal transduction in brain cells underlie the cognitive decline. The phosphorylation/dephosphorylation imbalance occurring in degenerating neurons was recently related to abnormal activity of one or more signal transduction pathways. AD is known to be associated with altered neuronal Ca<sup>2+</sup> homeostasis, as Ca<sup>2+</sup> accumulates in affected neurons leading to functional impairment. It is becoming more and more evident the involvement of signal transduction pathways acting upon Ca<sup>2+</sup> metabolism and phosphorylation regulation of proteins. A growing interest raised around the role of signal transduction systems in a number of human diseases including neurodegenerative diseases, with special regard to the systems related to the phosphoinositide (PI) pathway and AD. The PI signal transduction pathway plays a crucial role, being involved in a variety of cell functions, such as hormone secretion, neurotransmitter signal transduction, cell growth, membrane trafficking, ion channel activity, cytoskeleton regulation, cell cycle control, apoptosis, cell and tissue polarity, and contributes to regulate the Ca<sup>2+</sup> levels in the nervous tissue. Conclusion: A number of observations indicated that PI-specific phospholipase C (PLC) enzymes might be involved in the alteration of neurotransmission. To understand the role and the timing of action of the signalling pathways recruited during the brain morphology changes during the AD progression might help to elucidate the aetiopathogenesis of the disease, paving the way to prognosis refinement and/or novel molecular therapeutic strategies.

Hemostatically potent small molecular weight serine protease from Maclura spinosa (Roxb. ex Willd.) accelerates healing of subcutaneous dermal wounds in Swiss albino mice

Biologia ◽  
2019 ◽  
Vol 75 (1) ◽  
pp. 139-149
Author(s):  
Venkatesh Bommalapura Kulkarni ◽  
Raghu Ram Achar ◽  
Maheshwari Mahadevappa ◽  
Dinesh Sosalagere Manjegowda ◽  
Priya Babu Shubha ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Serine Protease ◽  
Small Molecular Weight ◽  
Swiss Albino Mice ◽  
Albino Mice

scholarly journals The Rab Geranylgeranyl Transferase Beta Subunit Is Essential for Embryo and Seed Development in Arabidopsis thaliana

2021 ◽  
Vol 22 (15) ◽  
pp. 7907
Author(s):  
Joanna Rojek ◽  
Matthew R. Tucker ◽  
Michał Rychłowski ◽  
Julita Nowakowska ◽  
Małgorzata Gutkowska
Keyword(s):  
Seed Development ◽  
Auxin Transport ◽  
Rab Proteins ◽  
Vesicular Traffic ◽  
Polar Localization ◽  
Reproductive Structures ◽  
Autonomous Endosperm ◽  
Endosperm Formation ◽  
Geranylgeranyl Transferase ◽  
Unfertilized Ovules

Auxin is a key regulator of plant development affecting the formation and maturation of reproductive structures. The apoplastic route of auxin transport engages influx and efflux facilitators from the PIN, AUX and ABCB families. The polar localization of these proteins and constant recycling from the plasma membrane to endosomes is dependent on Rab-mediated vesicular traffic. Rab proteins are anchored to membranes via posttranslational addition of two geranylgeranyl moieties by the Rab Geranylgeranyl Transferase enzyme (RGT), which consists of RGTA, RGTB and REP subunits. Here, we present data showing that seed development in the rgtb1 mutant, with decreased vesicular transport capacity, is disturbed. Both pre- and post-fertilization events are affected, leading to a decrease in seed yield. Pollen tube recognition at the stigma and its guidance to the micropyle is compromised and the seed coat forms incorrectly. Excess auxin in the sporophytic tissues of the ovule in the rgtb1 plants leads to an increased tendency of autonomous endosperm formation in unfertilized ovules and influences embryo development in a maternal sporophytic manner. The results show the importance of vesicular traffic for sexual reproduction in flowering plants, and highlight RGTB1 as a key component of sporophytic-filial signaling.

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

Biosynthesis of the Diguanosine Nucleotides. I. Purification and Properties of an Enzyme from Yolk Platelets of Brine Shrimp Embryos

1974 ◽  
Vol 52 (3) ◽  
pp. 231-240 ◽  
Author(s):  
A. H. Warner ◽  
P. C. Beers ◽  
F. L. Huang
Keyword(s):  
Molecular Weight ◽  
Brine Shrimp ◽  
Artemia Salina ◽  
Temperature Optimum ◽  
Small Molecular Weight ◽  
Ph Optimum ◽  
Optimal Activity ◽  
Purification And Properties

An enzyme that catalyzes the synthesis of P1P4-diguanosine 5′-tetraphosphate (Gp4G) has been isolated and purified from yolk platelets of encysted embryos of the brine shrimp, Artemia salina. The enzyme GTP:GTP guanylyltransferase (Gp4G synthetase) utilizes GTP as substrate, has a pH optimum of 5.9–6.0, a temperature optimum of 40–42 °C, and requires Mg2+ and dithiothreitol for optimal activity. The synthesis of Gp4G is inhibited markedly by pyrophosphate, whereas orthophosphate has no effect on the reaction. In the presence of GDP the enzyme also catalyzes the synthesis of P1,P3-diguanosine 5′-triphosphate (Gp3G), but the rate of synthesis is low compared with Gp4G synthesis and dependent upon other small molecular weight components of yolk platelets.

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