scholarly journals Chromogranin A Induces the Biogenesis of Granules with Calcium- and Actin-Dependent Dynamics and Exocytosis in Constitutively Secreting Cells

Endocrinology ◽  
2012 ◽  
Vol 153 (9) ◽  
pp. 4444-4456 ◽  
Author(s):  
Salah Elias ◽  
Charlène Delestre ◽  
Stéphane Ory ◽  
Sébastien Marais ◽  
Maïté Courel ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Chromogranin A ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Active Role ◽  
Subcellular Fractionation ◽  
Neuroendocrine Cells ◽  
Cortical Actin ◽  
Neuropeptide Secretion ◽  
Granule Membrane

Chromogranins are a family of acidic glycoproteins that play an active role in hormone and neuropeptide secretion through their crucial role in secretory granule biogenesis in neuroendocrine cells. However, the molecular mechanisms underlying their granulogenic activity are still not fully understood. Because we previously demonstrated that the expression of the major component of secretory granules, chromogranin A (CgA), is able to induce the formation of secretory granules in nonendocrine COS-7 cells, we decided to use this model to dissect the mechanisms triggered by CgA leading to the biogenesis and trafficking of such granules. Using quantitative live cell imaging, we first show that CgA-induced organelles exhibit a Ca2+-dependent trafficking, in contrast to native vesicle stomatitis virus G protein-containing constitutive vesicles. To identify the proteins that confer such properties to the newly formed granules, we developed CgA-stably-expressing COS-7 cells, purified their CgA-containing granules by subcellular fractionation, and analyzed the granule proteome by liquid chromatography-tandem mass spectrometry. This analysis revealed the association of several cytosolic proteins to the granule membrane, including GTPases, cytoskeleton-based molecular motors, and other proteins with actin- and/or Ca2+-binding properties. Furthermore, disruption of cytoskeleton affects not only the distribution and the transport but also the Ca2+-evoked exocytosis of the CgA-containing granules, indicating that these granules interact with microtubules and cortical actin for the regulated release of their content. These data demonstrate for the first time that the neuroendocrine factor CgA induces the recruitment of cytoskeleton-, GTP-, and Ca2+-binding proteins in constitutively secreting COS-7 cells to generate vesicles endowed with typical dynamics and exocytotic properties of neuroendocrine secretory granules.

Synaptic Transmission in the Immune System

e-Neuroforum ◽  
2017 ◽  
Vol 23 (4) ◽  
Author(s):  
Jens Rettig ◽  
David R. Stevens
Keyword(s):  
Nervous System ◽  
Immune System ◽  
Synaptic Transmission ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Neuroendocrine Cells ◽  
Regulated Exocytosis ◽  
Protein Receptor ◽  
Immunological Synapses ◽  
Immunological Diseases

AbstractThe release of neurotransmitters at synapses belongs to the most important processes in the central nervous system. In the last decades much has been learned about the molecular mechanisms which form the basis for this fundamental process. Highly regulated exocytosis, based on the SNARE (soluble N-ethylmaleimide-sensitive attachment protein receptor) complex and its regulatory molecules is the signature specialization of the nervous system and is shared by neurons and neuroendocrine cells. Cells of the immune system use a similar mechanism to release cytotoxic materials from secretory granules at contacts with virally or bacterially infected cells or cancer cells, in order to remove these threats. These contact zones have been termed immunological synapses in reference to the highly specific targeted exocytosis of effector molecules. Recent findings indicate that mutations in SNARE or SNARE-interacting proteins are the basis of a number of devastating immunological diseases. While SNARE complexes are ubiquitous and mediate a wide variety of membrane fusion events it is surprising that in many cases the SNARE proteins involved in immunological synapses are the same molecules which mediate regulated exocytosis of transmitters and hormones in neurons and neuroendocrine cells. These similarities raise the possibility that results obtained at immunological synapses may be applicable, in particular in the area of presynaptic function, to neuronal synapses. Since immunological synapses (IS) are assembled and disassembled in about a half an hour, the use of immune cells isolated from human blood allows not only the study of the molecular mechanisms of synaptic transmission in human cells, but is particularly suited to the examination of the assembly and disassembly of these “synapses” via live imaging. In this overview we discuss areas of similarity between synapses of the nervous and immune systems and in the process will refer to results of our experiments of the last few years.

scholarly journals Sorting and storage during secretory granule biogenesis: looking backward and looking forward

1998 ◽  
Vol 332 (3) ◽  
pp. 593-610 ◽  
Author(s):  
Peter ARVAN ◽  
David CASTLE
Keyword(s):  
Secretory Pathway ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Secretory Proteins ◽  
Membrane Composition ◽  
Granule Formation ◽  
Granule Membrane ◽  
Regulated Secretory Pathway ◽  
Secretory Products

Secretory granules are specialized intracellular organelles that serve as a storage pool for selected secretory products. The exocytosis of secretory granules is markedly amplified under physiologically stimulated conditions. While granules have been recognized as post-Golgi carriers for almost 40 years, the molecular mechanisms involved in their formation from the trans-Golgi network are only beginning to be defined. This review summarizes and evaluates current information about how secretory proteins are thought to be sorted for the regulated secretory pathway and how these activities are positioned with respect to other post-Golgi sorting events that must occur in parallel. In the first half of the review, the emerging role of immature secretory granules in protein sorting is highlighted. The second half of the review summarizes what is known about the composition of granule membranes. The numerous similarities and relatively limited differences identified between granule membranes and other vesicular carriers that convey products to and from the plasmalemma, serve as a basis for examining how granule membrane composition might be established and how its unique functions interface with general post-Golgi membrane traffic. Studies of granule formation in vitro offer additional new insights, but also important challenges for future efforts to understand how regulated secretory pathways are constructed and maintained.

scholarly journals Electron microscopic localization of chromogranin A in osmium-fixed neuroendocrine cells with a protein A-gold technique.

1987 ◽  
Vol 35 (7) ◽  
pp. 795-801 ◽  
Author(s):  
S A Hearn
Keyword(s):  
Neuroendocrine Tumors ◽  
Chromogranin A ◽  
Osmium Tetroxide ◽  
Secretory Granules ◽  
Protein A ◽  
Neuroendocrine Cells ◽  
Neurosecretory Granules ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Carotid Body Tumors

An antibody (LK2H10) to chromogranin A has been recommended for use in ultrastructural identification of neuroendocrine secretory granules. Previous studies have demonstrated immunoreactive chromogranin A in specimens prepared for electron microscopy by glutaraldehyde fixation only. In this study, the effect of specimen post-fixation by osmium tetroxide on post-embedding localization of chromogranin A was evaluated. Human tissues from benign endocrine glands, neuroendocrine tumors, and non-neuroendocrine tumors were post-fixed in osmium, embedded in epoxy resin, and the sample thin sections immunolabeled using a protein A-gold technique. Chromogranin A-positive neurosecretory granules were detected in pancreatic islets, adrenal medulla, stomach, ileum, anterior pituitary, and parathyroid. Mid-gut carcinoids, bronchial carcinoids, pheochromocytomas, paragangliomas, carotid body tumors, and thyroid medullary carcinomas contained immunoreactive granules. Cytoplasmic granules in non-neuroendocrine tumors did not react for chromogranin A. Tissues post-fixed in osmium tetroxide had optimally preserved ultrastructural features, and use of this fixative is compatible with postembedding localization of chromogranin A in neurosecretory granules.

Tunneling nanotubes and related structures: molecular mechanisms of formation and function

2021 ◽  
Vol 478 (22) ◽  
pp. 3977-3998
Author(s):  
Sunayana Dagar ◽  
Diksha Pathak ◽  
Harsh V. Oza ◽  
Sivaram V. S. Mylavarapu
Keyword(s):  
Molecular Motors ◽  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Cell Communication ◽  
Microbial Pathogens ◽  
Actin Dynamics ◽  
Cortical Actin ◽  
Animal Cells ◽  
Tunneling Nanotubes ◽  
And Function

Tunneling nanotubes (TNTs) are F-actin-based, membrane-enclosed tubular connections between animal cells that transport a variety of cellular cargo. Over the last 15 years since their discovery, TNTs have come to be recognized as key players in normal cell communication and organism development, and are also exploited for the spread of various microbial pathogens and major diseases like cancer and neurodegenerative disorders. TNTs have also been proposed as modalities for disseminating therapeutic drugs between cells. Despite the rapidly expanding and wide-ranging relevance of these structures in both health and disease, there is a glaring dearth of molecular mechanistic knowledge regarding the formation and function of these important but enigmatic structures. A series of fundamental steps are essential for the formation of functional nanotubes. The spatiotemporally controlled and directed modulation of cortical actin dynamics would be required to ensure outward F-actin polymerization. Local plasma membrane deformation to impart negative curvature and membrane addition at a rate commensurate with F-actin polymerization would enable outward TNT elongation. Extrinsic tactic cues, along with cognate intrinsic signaling, would be required to guide and stabilize the elongating TNT towards its intended target, followed by membrane fusion to create a functional TNT. Selected cargoes must be transported between connected cells through the action of molecular motors, before the TNT is retracted or destroyed. This review summarizes the current understanding of the molecular mechanisms regulating these steps, also highlighting areas that deserve future attention.

scholarly journals Actin and Myosin in Non-Neuronal Exocytosis

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1455 ◽  
Author(s):  
Pika Miklavc ◽  
Manfred Frick
Keyword(s):  
Molecular Motors ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Cell Cortex ◽  
Secretory Cells ◽  
Secretory Vesicles ◽  
Cortical Actin ◽  
Myosin V ◽  
Myosin I

Cellular secretion depends on exocytosis of secretory vesicles and discharge of vesicle contents. Actin and myosin are essential for pre-fusion and post-fusion stages of exocytosis. Secretory vesicles depend on actin for transport to and attachment at the cell cortex during the pre-fusion phase. Actin coats on fused vesicles contribute to stabilization of large vesicles, active vesicle contraction and/or retrieval of excess membrane during the post-fusion phase. Myosin molecular motors complement the role of actin. Myosin V is required for vesicle trafficking and attachment to cortical actin. Myosin I and II members engage in local remodeling of cortical actin to allow vesicles to get access to the plasma membrane for membrane fusion. Myosins stabilize open fusion pores and contribute to anchoring and contraction of actin coats to facilitate vesicle content release. Actin and myosin function in secretion is regulated by a plethora of interacting regulatory lipids and proteins. Some of these processes have been first described in non-neuronal cells and reflect adaptations to exocytosis of large secretory vesicles and/or secretion of bulky vesicle cargoes. Here we collate the current knowledge and highlight the role of actomyosin during distinct phases of exocytosis in an attempt to identify unifying molecular mechanisms in non-neuronal secretory cells.

scholarly journals The role of chromogranin-A and its derived peptide, WE-14 in the development of type 1 diabetes mellitus

2015 ◽  
Vol 156 (5) ◽  
pp. 163-170
Author(s):  
Zoltán Herold ◽  
Péter Nagy ◽  
Attila Patócs ◽  
Anikó Somogyi
Keyword(s):  
Diabetes Mellitus ◽  
Type 1 Diabetes ◽  
Type 1 Diabetes Mellitus ◽  
Chromogranin A ◽  
Neuroendocrine Tumour ◽  
Secretory Granules ◽  
Neuroendocrine Cells ◽  
Diabetic Patients ◽  
Autoreactive Cells

Chromogranin-A is a member of the granine protein family. It is produced in neuroendocrine cells via secretory granules. Many cleavage proteins are formed from chromogranin-A, from which some have well known biological activity, while the function of others is not yet fully known. Serum chromogranin-A levels are used in neuroendocrine tumour diagnostics. Recent studies showed that one of its cleavage protein, WE-14 may also play a role in the development of type 1 diabetes. WE-14 may function as an autoantigen for T-cells involved in the destruction of β-cells. This mechanism was previously observed only in non-obese diabetic mice. Novel results show that WE-14 also serves as a target for autoreactive cells in newly diagnosed type 1 diabetic patients as well, which reaction can be increased with transglutaminase. In this paper the authors summarize the recent knowledge about chromogranin-A and its potential role in the pathomechanism of type 1 diabetes mellitus. Orv. Hetil., 2015, 156(5), 163–170.

scholarly journals Homotypic Fusion of Immature Secretory Granules During Maturation Requires Syntaxin 6

2001 ◽  
Vol 12 (6) ◽  
pp. 1699-1709 ◽  
Author(s):  
Franz Wendler ◽  
Lesley Page ◽  
Sylvie Urbé ◽  
Sharon A. Tooze
Keyword(s):  
Fusion Protein ◽  
Indirect Immunofluorescence ◽  
Immunofluorescence Microscopy ◽  
Secretory Granules ◽  
Subcellular Fractionation ◽  
Neuroendocrine Cells ◽  
The Core ◽  
Indirect Immunofluorescence Microscopy ◽  
A Cell ◽  
Protein Attachment

Homotypic fusion of immature secretory granules (ISGs) gives rise to mature secretory granules (MSGs), the storage compartment in endocrine and neuroendocrine cells for hormones and neuropeptides. With the use of a cell-free fusion assay, we investigated which soluble N-ethylmaleimide-sensitive fusion protein attachment receptor (SNARE) molecules are involved in the homotypic fusion of ISGs. Interestingly, the SNARE molecules mediating the exocytosis of MSGs in neuroendocrine cells, syntaxin 1, SNAP-25, and VAMP2, were not involved in homotypic ISG fusion. Instead, we have identified syntaxin 6 as a component of the core machinery responsible for homotypic ISG fusion. Subcellular fractionation studies and indirect immunofluorescence microscopy show that syntaxin 6 is sorted away during the maturation of ISGs to MSGs. Although, syntaxin 6 on ISG membranes is associated with SNAP-25 and SNAP-29/GS32, we could not find evidence that these target (t)-SNARE molecules are involved in homotypic ISG fusion. Nor could we find any involvement for the vesicle (v)-SNARE VAMP4, which is known to be associated with syntaxin 6. Importantly, we have shown that homotypic fusion requires the function of syntaxin 6 on both donor as well as acceptor membranes, which suggests that t–t-SNARE interactions, either direct or indirect, may be required during fusion of ISG membranes.

Differential distribution of mannose-6-phosphate receptors and furin in immature secretory granules

1999 ◽  
Vol 112 (22) ◽  
pp. 3955-3966 ◽  
Author(s):  
A.S. Dittie ◽  
J. Klumperman ◽  
S.A. Tooze
Keyword(s):  
Fusion Proteins ◽  
Secretory Granules ◽  
Adaptor Protein ◽  
Subcellular Fractionation ◽  
Neuroendocrine Cells ◽  
Differential Distribution ◽  
A Cell ◽  
Mannose 6 Phosphate ◽  
The Relationship

In neuroendocrine cells sorting of proteins from immature secretory granules (ISGs) occurs during maturation and is achieved by clathrin-coated vesicles containing the adaptor protein (AP)-1. We have investigated the role of the mannose-6-phosphate receptors (M6PRs) in the recruitment of AP-1 to ISGs. M6PRs were detected in ISGs isolated from PC12 cells by subcellular fractionation, and by immuno-EM labelling on cryosections. In light of our previous results, where greater than 80% of the ISGs were found to contain furin, we examined the relationship between furin and M6PR on ISGs. By immunoisolation techniques we find that 50% at most of the ISGs contain the cation-independent (CI)-M6PR. Using sequential immunoisolation we could demonstrate that there are two populations of ISGs: those that have both M6PR and furin, and those which contain only furin. Furthermore, using immobilized GST-fusion proteins containing the cytoplasmic domain of the CI-M6PR we have shown binding of AP-1 requires casein kinase II phosphorylation of the CI-M6PR fusion protein, and in particular phosphorylation of Ser(2474). Addition of these phosphorylated GST-CI-M6PR fusion proteins to a cell-free assay reconstituting AP-1 binding to ISGs inhibits AP-1 recruitment to ISGs.

scholarly journals Chromogranin-A as a Serum Marker for Neuroendocrine Tumors: Comparison with Neuron-Specific Enolase and Correlation with Immunohistochemical Findings

1999 ◽  
Vol 14 (3) ◽  
pp. 160-166 ◽  
Author(s):  
L. Giovanella ◽  
S. la Rosa ◽  
L. Ceriani ◽  
S. Uccella ◽  
P. Erba ◽  
...  
Keyword(s):  
Neuroendocrine Tumors ◽  
Chromogranin A ◽  
Secretory Granules ◽  
Neuron Specific Enolase ◽  
Serum Levels ◽  
Tissue Expression ◽  
Neuroendocrine Cells ◽  
Analytical Performance ◽  
Helical Computed Tomography ◽  
Tumor Extent

Background Chromogranin-A (Cg-A) is a 439-amino-acid protein contained in secretory granules of neuroendocrine cells, in addition to specific hormone peptides or neuropeptides. Since Cg-A is co-released with peptide hormones its serum concentration can be used as a marker of neuroendocrine tumors. Aim Evaluation of the analytical performance of a new IRMA method for Cg-A assay and of the clinical value of serum Cg-A and neuron-specific enolase (NSE) in neuroendocrine tumors. In addition, we compared the diagnostic usefulness of both Cg-A and NSE serum levels and their relationship to tissue expression. Patients and methods Initially we evaluated the analytical performance (intra- and interassay imprecision, dilution test and detection limit) of the Cg-A RIACT method (CIS Bio-International, Gifsur-Yvette, France). We selected 50 patients affected by various histologically confirmed neuroendocrine tumors (NETs): 111In-pentetreotide scan and helical computed tomography were employed to assess tumor extent. Cg-A and NSE were measured before surgery in serum samples of patients and 50 age-matched controls by IRMA methods. After surgery immunohistochemical stains for Cg-A and NSE were performed on surgical specimens of tumor tissue. Results Cg-A levels were significantly higher (p<0.0001) in patients with NETs than in healthy controls and we found a positive correlation between serum and tissue expression (p<0.05). Serum levels of Cg-A were also related to tumor extent (p<0.05) but in some cases we observed significant elevation of serum Cg-A in small, intensely immunoreactive NETs. ROC curve analysis showed better accuracy for serum Cg-A compared to NSE in the diagnosis of NETs, while no significant relationship was found between serum expression and immunostaining for NSE. Discussion Our results confirmed the biological and clinical significance of circulating Cg-A as an expression of granular content in neuroendocrine tissues and supported the complementary usefulness of serum Cg-A in the diagnosis and evaluation of NETs together with imaging modalities.

scholarly journals Kalirin/Trio Rho Guanine Nucleotide Exchange Factors Regulate a Novel Step in Secretory Granule Maturation

2007 ◽  
Vol 18 (12) ◽  
pp. 4813-4825 ◽  
Author(s):  
Francesco Ferraro ◽  
Xin-Ming Ma ◽  
Jacqueline A. Sobota ◽  
Betty A. Eipper ◽  
Richard E. Mains
Keyword(s):  
Secretory Granule ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Guanine Nucleotide Exchange Factors ◽  
Neuroendocrine Cells ◽  
Secretory Cells ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors

The molecular mechanisms involved in the maturation of secretory granules, organelles that store hormones and neuropeptides, are poorly understood. As granule content proteins are processed, the composition of granule membranes changes, yielding constitutive-like secretion of immature content proteins and producing secretagogue-responsive mature granules. Constitutive-like secretion was not previously recognized as a process subject to regulation. We show that Kalirin and Trio, homologous Rho guanine nucleotide exchange factors (GEFs), which interact with a secretory granule resident protein, modulate cargo secretion from immature granules. Some of the Kalirin and Trio isoforms expressed in neuroendocrine cells colocalize with immature granules. Overexpression of their N-terminal GEF domain (GEF1) enhances secretion from immature granules, depleting cells of secretory cargo in the absence of secretagogue. This response requires GEF1 activity and is mimicked by Kalirin/Trio substrates Rac1 and RhoG. Accordingly, selective pharmacological inhibition of endogenous GEF1 activity decreases secretagogue-independent release of hormone precursors, accumulating product peptide in mature secretory granules. Kalirin/Trio modulation of cargo secretion from immature granules provides secretory cells with an extra layer of control over the sets of peptides released. Control of this step enhances the range of physiological responses that can be elicited, whereas lack of control could have pathological consequences.

Sign in / Sign up

Export Citation Format

Share Document