Adhesion of Salmonella to Pancreatic Secretory Granule Membrane Major Glycoprotein GP2 of Human and Porcine Origin Depends on FimH Sequence Variation

After enzyme secretion the membrane of the secretory granule, which had been fused to the cell membrane, was resorbed into the cell. Experiments were therefore carried out to test whether formation of new secretory granules involves reutilization of the resorbed membrane or synthesis of a new membrane, de novo, from amino acids. Incorporation of amino acids-14C into proteins of various cell fractions was measured in vivo, 30, 120, and. 300 min after labeling. At all times the specific radioactivity of the secretory granule membrane was about equal to that of the granule's exportable content. At 120 and 300 min the specific radioactivity of the granule membrane and of the granule content was much higher than that of any other subcellular fraction. It is therefore concluded that the protein of the membrane is synthesized de novo concomitantly with the exportable protein. The proteins of the granule membrane could be distinguished from those of the granule content by gel electrophoresis. All major bands were labeled proportionately to their staining intensity. The amino acid composition of the secretory granule membrane was markedly different from that of the granule's content and also from that of the mitochondrial membrane. The granule membrane showed a high proline content, 30 moles/100 moles amino acids. The analyses show that the radioactivity of the granule membrane is indeed inherent in its proteins and is not due to contamination by other fractions. The possibility is considered that the exportable protein leaves the endoplasmic reticulum already enveloped by the newly synthesized membrane.

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Control of Exocytosis in Single Cells

Physiology ◽

10.1152/physiologyonline.1989.4.2.53 ◽

1989 ◽

Vol 4 (2) ◽

pp. 53-56 ◽

Cited By ~ 1

Author(s):

Y Maruyama

Keyword(s):

Membrane Fusion ◽

G Proteins ◽

Secretory Granule ◽

Single Cells ◽

Guanine Nucleotide ◽

Signal Transducers ◽

Granule Membrane ◽

Guanine Nucleotide Binding ◽

Nucleotide Binding Proteins ◽

Guanine Nucleotide Binding Proteins

Exocytosis can be quantified by measuring changes in membrane capacitance in single internally perfused cells. Exocytosis is controlled by guanine nucleotide-binding proteins (G proteins) acting as key signal transducers. Different G proteins mediate receptor signaling and secretory granule-membrane fusion.

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Small G proteins as key regulators of pancreatic digestive enzyme secretion

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.90874.2008 ◽

2009 ◽

Vol 296 (3) ◽

pp. E405-E414 ◽

Cited By ~ 30

Author(s):

John A. Williams ◽

Xuequn Chen ◽

Maria E. Sabbatini

Keyword(s):

G Proteins ◽

Secretory Granule ◽

Secretory Pathway ◽

Digestive Enzyme ◽

Pancreatic Acinar Cells ◽

Cellular Processes ◽

Granule Membrane ◽

Target Membrane ◽

Rho Family ◽

Small G Proteins

Small GTP-binding (G) proteins act as molecular switches to regulate a number of cellular processes, including vesicular transport. Emerging evidence indicates that small G proteins regulate a number of steps in the secretion of pancreatic acinar cells. Diverse small G proteins have been localized at discrete compartments along the secretory pathway and particularly on the secretory granule. Rab3D, Rab27B, and Rap1 are present on the granule membrane and play a role in the steps leading up to exocytosis. Whether the function of these G proteins is simply to ensure appropriate targeting or if they are involved as regulatory molecules is discussed. Most evidence suggests that Rab3D and Rab27B play a role in tethering the secretory granule to its target membrane. Other Rabs have been identified on the secretory granule that are associated with different steps in the secretory pathway. The Rho family small G proteins RhoA and Rac1 also regulate secretion through remodeling of the actin cytoskeleton. Possible mechanisms for regulation of these G proteins and their effector molecules are considered.

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Secretion-related uptake of horseradish peroxidase in neurohypophysial axons.

The Journal of Cell Biology ◽

10.1083/jcb.70.2.294 ◽

1976 ◽

Vol 70 (2) ◽

pp. 294-303 ◽

Cited By ~ 51

Author(s):

D T Theodosis ◽

J Dreifuss ◽

M C Harris ◽

L Orci

Keyword(s):

Plasma Membrane ◽

Electrical Stimulation ◽

Horseradish Peroxidase ◽

Secretory Granule ◽

Morphometric Analysis ◽

Neurosecretory Granules ◽

Neurohypophysial Hormones ◽

Axon Terminals ◽

Granule Membrane ◽

Stimulation Of

During secretion of the neurohypophysial hormones, oxytocin and vasopressin, secretory granule membrane is added to the plasma membrane of the axon terminals. It is generally assumed that subsequent internalization of this additional membrane occurs by endocytosis. In order to study this process, we have traced the uptake of intravenously injected horseradish peroxidase by neurohypophysial axons in rats and golden hamsters. Peroxidase reaction product within the secretory axons was found mainly in vacuolar and C-shaped structures of a size comparable with or larger than the neurosecretory granules. Our observations suggest that these large horseradish peroxidase (HRP)-impregnated vacuoles arise directly by a form of macropinocytosis. Morphometric analysis indicated that this form of membrane retrieval increased significantly after the two types of stimuli used, reversible hemorrhage and electrical stimulation of the pituitary stalk. Microvesicular uptake of HRP was found to be comparatively less.

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Secretory Granule Growth Hormone and Prolactin Release: Independence from Granule Membrane ATPase*

Endocrinology ◽

10.1210/endo-114-3-717 ◽

1984 ◽

Vol 114 (3) ◽

pp. 717-724 ◽

Cited By ~ 2

Author(s):

MARY Y. LORENSON ◽

LAURENCE S. JACOBS

Keyword(s):

Growth Hormone ◽

Secretory Granule ◽

Prolactin Release ◽

Membrane Atpase ◽

Granule Membrane ◽

Granule Growth

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Evidence for G proteins in rat parotid plasma membranes and secretory granule membranes

Biochemical Journal ◽

10.1042/bj2850441 ◽

1992 ◽

Vol 285 (2) ◽

pp. 441-449 ◽

Cited By ~ 19

Author(s):

E L Watson ◽

D DiJulio ◽

D Kauffman ◽

J Iversen ◽

M R Robinovitch ◽

...

Keyword(s):

Plasma Membrane ◽

G Proteins ◽

Secretory Granule ◽

Membrane Fraction ◽

Immunoblot Analysis ◽

Plasma Membrane Fraction ◽

Adp Ribosylation ◽

Granule Membrane ◽

Rat Parotid ◽

Gs Alpha

G proteins were identified in rat parotid plasma membrane-enriched fractions and in two populations of isolated secretory granule membrane fractions. Both [32P]ADP-ribosylation analysis with bacterial toxins and immunoblot analysis with crude and affinity-purified antisera specific for alpha subunits of G proteins were utilized. Pertussis toxin catalysed the ADP-ribosylation of a 41 kDa substrate in the plasma membrane fraction and both secretory granule membrane fractions. Cholera toxin catalysed the ADP-ribosylation of two substrates with molecular masses of 44 kDa and 48 kDa in the plasma membrane fraction but not in the secretory granule fractions. However, these substrates were detected in the secretory granule fractions when recombinant ADP-ribosylating factor was present in the assay medium. Immunoblot analysis of rat parotid membrane fractions using both affinity-purified and crude antisera revealed strong immunoreactivity of these membranes with anti-Gs alpha, -Gi alpha 1/alpha 2 and -Gi alpha 3 sera. In contrast Gs alpha was the major substrate found in both of the secretory granule fractions. Granule membrane fractions also reacted moderately with anti-Gi alpha 3 antiserum, and weakly with anti-Gi alpha 1/alpha 2 and -G(o) alpha sera. The results demonstrate that the parotid gland membranes express a number of G proteins. The presence of G proteins in secretory granule membranes suggests that they may play a direct role in regulating exocytosis in exocrine glands.

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Mistargeting of secretory cargo in retromer-deficient cells

Disease Models & Mechanisms ◽

10.1242/dmm.046417 ◽

2020 ◽

pp. dmm.046417

Author(s):

Sarah D. Neuman ◽

Erica L. Terry ◽

Jane E. Selegue ◽

Amy T. Cavanagh ◽

Arash Bashirullah

Keyword(s):

Membrane Proteins ◽

Salivary Glands ◽

Secretory Granule ◽

Complex Function ◽

Amyloid Β ◽

Secretory Cells ◽

Regulated Exocytosis ◽

Retromer Complex ◽

Granule Membrane ◽

Granule Membrane Proteins

Intracellular trafficking is a basic and essential cellular function required for delivery of proteins to the appropriate subcellular destination; this process is especially demanding in professional secretory cells, which synthesize and secrete massive quantities of cargo proteins via regulated exocytosis. The Drosophila larval salivary glands are professional secretory cells that synthesize and secrete mucin proteins at the onset of metamorphosis. Using the larval salivary glands as a model system, we have identified a role for the highly conserved retromer complex in trafficking of secretory granule membrane proteins. We demonstrate that retromer-dependent trafficking via endosomal tubules is induced at the onset of secretory granule biogenesis, and that recycling via endosomal tubules is required for delivery of essential secretory granule membrane proteins to nascent granules. Without retromer function, nascent granules do not contain the proper membrane proteins; as a result, cargo from these defective granules is mistargeted to Rab7-positive endosomes, where it progressively accumulates to generate dramatically enlarged endosomes. Retromer complex dysfunction is strongly associated with neurodegenerative diseases, including Alzheimer's disease, characterized by accumulation of amyloid β (Aβ). We show that ectopically expressed amyloid precursor protein (APP) undergoes regulated exocytosis in salivary glands and accumulates within enlarged endosomes in retromer-deficient cells. These results highlight recycling of secretory granule membrane proteins as a critical step during secretory granule maturation and provide new insights into our understanding of retromer complex function in secretory cells. These findings also suggest that missorting of secretory cargo, including APP, may contribute to the progressive nature of neurodegenerative disease.

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Melanophilin accelerates insulin granule fusion without predocking to the plasma membrane

10.2337/figshare.12990773.v1 ◽

2020 ◽

Author(s):

Ada Admin ◽

Hao Wang ◽

Kouichi Mizuno ◽

Noriko Takahashi ◽

Eri Kobayashi ◽

...

Keyword(s):

Plasma Membrane ◽

Secretory Granule ◽

Β Cells ◽

Pancreatic Β Cells ◽

Granule Exocytosis ◽

Synaptic Vesicle Exocytosis ◽

Granule Membrane ◽

Myosin Va ◽

Vesicle Exocytosis ◽

Glucose Stimulated Insulin Secretion

Direct observation of fluorescence-labeled secretory granule exocytosis in living pancreatic β cells has revealed heterogeneous prefusion behaviors: some granules dwell beneath the plasma membrane before fusion, while others fuse immediately once they are recruited to the plasma membrane. Although the former mode seems to follow sequential docking-priming-fusion steps as found in synaptic vesicle exocytosis, the latter mode, which is unique to secretory granule exocytosis, has not been explored well. Here, we show that melanophilin, one of the effectors of the monomeric GTPase Rab27 on the granule membrane, is involved in such an accelerated mode of exocytosis. Both melanophilin-mutated leaden mouse and melanophilin-downregulated human pancreatic β cells exhibit impaired glucose-stimulated insulin secretion, with a specific reduction in fusion events that bypass stable docking to the plasma membrane. Upon stimulus-induced [Ca2+]i rise, melanophilin mediates this type of fusion by dissociating granules from myosin-Va and actin in the actin cortex and by associating them with a fusion-competent, open form of syntaxin-4 on the plasma membrane. These findings provide the hitherto unknown mechanism to support sustainable exocytosis by which granules are recruited from the cell interior and fuse promptly without stable predocking to the plasma membrane.

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