Secretome and Tunneling Nanotubes: A Multilevel Network for Long Range Intercellular Communication between Endothelial Cells and Distant Cells

As a cellular interface between the blood and tissues, the endothelial cell (EC) monolayer is involved in the control of key functions including vascular tone, permeability and homeostasis, leucocyte trafficking and hemostasis. EC regulatory functions require long-distance communications between ECs, circulating hematopoietic cells and other vascular cells for efficient adjusting thrombosis, angiogenesis, inflammation, infection and immunity. This intercellular crosstalk operates through the extracellular space and is orchestrated in part by the secretory pathway and the exocytosis of Weibel Palade Bodies (WPBs), secretory granules and extracellular vesicles (EVs). WPBs and secretory granules allow both immediate release and regulated exocytosis of messengers such as cytokines, chemokines, extracellular membrane proteins, coagulation or growth factors. The ectodomain shedding of transmembrane protein further provide the release of both receptor and ligands with key regulatory activities on target cells. Thin tubular membranous channels termed tunneling nanotubes (TNTs) may also connect EC with distant cells. EVs, in particular exosomes, and TNTs may contain and transfer different biomolecules (e.g., signaling mediators, proteins, lipids, and microRNAs) or pathogens and have emerged as a major triggers of horizontal intercellular transfer of information.

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Molecular probing of the secretory pathway in peptide hormone-producing cells

Journal of Cell Science ◽

10.1242/jcs.108.10.3295 ◽

1995 ◽

Vol 108 (10) ◽

pp. 3295-3305 ◽

Cited By ~ 1

Author(s):

J.C. Holthuis ◽

E.J. Jansen ◽

M.C. van Riel ◽

G.J. Martens

Keyword(s):

Secretory Pathway ◽

Transmembrane Protein ◽

Secretory Granules ◽

Peptide Hormone ◽

Mrna Levels ◽

Black And White ◽

Processing Enzymes ◽

Black Background ◽

Prohormone Processing ◽

Associated Proteins

The biosynthetic machinery in the melanotrope cells of the Xenopus intermediate pituitary is primarily dedicated to the generation of proopiomelanocortin (POMC)-derived, melanophore-stimulating peptides. Transfer of the animal to a black background stimulates the production of these peptides and causes a dramatic increase in POMC mRNA levels. To identify genes involved in the biosynthesis and regulated release of peptide hormones, we differentially screened an intermediate pituitary cDNA library of toads adapted to a black background with cDNA probes derived from intermediate pituitary mRNA of black- and white-adapted animals. Here we report the identification of twelve distinct genes whose expression levels in the melanotropes are regulated in coordination with that of POMC. Four of these genes are novel while the others code for translocon-associated proteins, a lumenal cysteine protease of the endoplasmic reticulum, prohormone-processing enzymes, members of the granin family and a transmembrane protein presumably involved in the assembly and/or specific functioning of vacuolar H(+)-ATPase from secretory granules. Our results indicate that a wide variety of both soluble and membrane-associated components of the secretory pathway is recruited in physiologically activated, peptide hormone-producing cells.

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Colocalization of chaperone Cpn60, proinsulin and convertase PC1 within immature secretory granules of insulin-secreting cells suggests a role for Cpn60 in insulin processing

Journal of Cell Science ◽

10.1242/jcs.113.11.2075 ◽

2000 ◽

Vol 113 (11) ◽

pp. 2075-2083 ◽

Cited By ~ 1

Author(s):

A.E. Arias ◽

C.S. Velez-Granell ◽

G. Mayer ◽

M. Bendayan

Keyword(s):

Islet Cell ◽

Secretory Pathway ◽

Secretory Granules ◽

Double Labeling ◽

In Vitro Binding ◽

Cell Extracts ◽

Vitro Binding ◽

Preferential Binding ◽

Insulin Secreting Cells

Many of the mechanisms that control insulin processing and packaging by interaction with different elements along the secretory pathway remain poorly understood. We have investigated the possibility that Cpn60, a member of the heat shock protein family, may be present in rat insulin-secreting cells, participating in the proinsulin-insulin maturation process. Immunofluorescence and high resolution immunocytochemical studies revealed the presence of the Cpn60 protein all along the insulin secretory pathway, being particularly abundant over the proinsulin-containing immature secretory granules. Double-labeling experiments showed associations between Cpn60 and proinsulin, as well as between Cpn60 and PC1 convertase, with a preferential binding to proinsulin. These findings paralleled those of coimmunoprecipitation studies showing the Cpn60 chaperone and the mature form of the PC1 convertase in proinsulin immunoprecipitates, as well as the PC1 in Cpn60 immunoprecipitates from total islet cell extracts. In vitro binding of Cpn60 to proinsulin, insulin and glucagon was also documented. Cpn60, significantly abundant in proinsulin-containing secretory granules where conversion of proinsulin to insulin takes place, and the colocalization of the chaperone with proinsulin and PC1 convertase suggest that the Cpn60 protein may play a role directing precise molecular interactions during insulin processing and/or packaging.

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

Biochemical Journal ◽

10.1042/bj3320593 ◽

1998 ◽

Vol 332 (3) ◽

pp. 593-610 ◽

Cited By ~ 363

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.

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Functional Mapping of Regions Involved in the Negative Imprinting of Virion Particle Infectivity and in Target Cell Protection by Interferon-Induced Transmembrane Protein 3 against HIV-1

Journal of Virology ◽

10.1128/jvi.01716-18 ◽

2018 ◽

Vol 93 (2) ◽

Cited By ~ 6

Author(s):

Romain Appourchaux ◽

Mathilde Delpeuch ◽

Li Zhong ◽

Julien Burlaud-Gaillard ◽

Kevin Tartour ◽

...

Keyword(s):

Target Cell ◽

Transmembrane Protein ◽

Regulatory Role ◽

Target Cells ◽

Restriction Factors ◽

Cell Protection ◽

Differential Behavior ◽

Antiviral Activities ◽

Divergent Behavior ◽

Hiv 1

ABSTRACT The interferon-induced transmembrane proteins (IFITMs) are a family of highly related antiviral factors that affect numerous viruses at two steps: in target cells by sequestering incoming viruses in endosomes and in producing cells by leading to the production of virions that package IFITMs and exhibit decreased infectivity. While most studies have focused on the former, little is known about the regulation of the negative imprinting of virion particle infectivity by IFITMs and about its relationship with target cell protection. Using a panel of IFITM3 mutants against HIV-1, we have explored these issues as well as others related to the biology of IFITM3, in particular virion packaging, stability, the relation to CD63/multivesicular bodies (MVBs), the modulation of cholesterol levels, and the relationship between negative imprinting of virions and target cell protection. The results that we have obtained exclude a role for cholesterol and indicate that CD63 accumulation does not directly relate to an antiviral behavior. We have defined regions that modulate the two antiviral properties of IFITM3 as well as novel domains that modulate protein stability and that, in so doing, influence the extent of its packaging into virions. The results that we have obtained, however, indicate that, even in the context of an IFITM-susceptible virus, IFITM3 packaging is not sufficient for negative imprinting. Finally, while most mutations concomitantly affect target cell protection and negative imprinting, a region in the C-terminal domain (CTD) exhibits a differential behavior, potentially highlighting the regulatory role that this domain may play in the two antiviral activities of IFITM3. IMPORTANCE IFITM proteins have been associated with the sequestration of incoming virions in endosomes (target cell protection) and with the production of virion particles that incorporate IFITMs and exhibit decreased infectivity (negative imprinting of virion infectivity). How the latter is regulated and whether these two antiviral properties are related remain unknown. By examining the behavior of a large panel of IFITM3 mutants against HIV-1, we determined that IFITM3 mutants are essentially packaged into virions proportionally to their intracellular levels of expression. However, even in the context of an IFITM-susceptible virus, IFITM3 packaging is not sufficient for the antiviral effects. Most mutations were found to concomitantly affect both antiviral properties of IFITM3, but one CTD mutant exhibited a divergent behavior, possibly highlighting a novel regulatory role for this domain. These findings thus advance our comprehension of how this class of broad antiviral restriction factors acts.

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PACS-1 and Adaptor Protein-1 Mediate ACTH Trafficking to the Regulated Secretory Pathway

10.1101/446229 ◽

2018 ◽

Author(s):

Brennan S. Dirk ◽

Christopher End ◽

Emily N. Pawlak ◽

Logan R. Van Nynatten ◽

Rajesh Abraham Jacob ◽

...

Keyword(s):

Membrane Trafficking ◽

Secretory Pathway ◽

Secretory Granules ◽

Adaptor Protein ◽

Cell Types ◽

Cellular Membrane ◽

Extracellular Milieu ◽

Specialized Form ◽

Regulated Secretory Pathway ◽

Clathrin Adaptor

ABSTRACTThe regulated secretory pathway is a specialized form of protein secretion found in endocrine and neuroendocrine cell types. Pro-opiomelanocortin (POMC) is a pro-hormone that utilizes this pathway to be trafficked to dense core secretory granules (DCSGs). Within this organelle, POMC is processed to multiple bioactive hormones that play key roles in cellular physiology. However, the complete set of cellular membrane trafficking proteins that mediate the correct sorting of POMC to DCSGs remain unknown. Here, we report the roles of the phosphofurin acidic cluster sorting protein – 1 (PACS-1) and the clathrin adaptor protein 1 (AP-1) in the targeting of POMC to DCSGs. Upon knockdown of PACS-1 and AP-1, POMC is readily secreted into the extracellular milieu and fails to be targeted to DCSGs.

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CMTM5-v1, a four-transmembrane protein, presents a secreted form released via a vesicle-mediated secretory pathway

BMB Reports ◽

10.5483/bmbrep.2010.43.3.182 ◽

2010 ◽

Vol 43 (3) ◽

pp. 182-187 ◽

Cited By ~ 9

Author(s):

Henan Li ◽

Xiaohuan Guo ◽

Luning Shao ◽

Markus Plate ◽

Xiaoning Mo ◽

...

Keyword(s):

Secretory Pathway ◽

Transmembrane Protein

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An antibody against secretogranin I (chromogranin B) is packaged into secretory granules.

The Journal of Cell Biology ◽

10.1083/jcb.109.1.17 ◽

1989 ◽

Vol 109 (1) ◽

pp. 17-34 ◽

Cited By ~ 73

Author(s):

P Rosa ◽

U Weiss ◽

R Pepperkok ◽

W Ansorge ◽

C Niehrs ◽

...

Keyword(s):

Secretory Pathway ◽

Secretory Granules ◽

Intracellular Localization ◽

Secretory Protein ◽

Secretory Proteins ◽

Chromogranin B ◽

Double Labeling ◽

Protein Protein Interaction ◽

And Function ◽

Secretogranin I

We have investigated the sorting and packaging of secretory proteins into secretory granules by an immunological approach. An mAb against secretogranin I (chromogranin B), a secretory protein costored with various peptide hormones and neuropeptides in secretory granules of many endocrine cells and neurons, was expressed by microinjection of its mRNA into the secretogranin I-producing cell line PC12. An mAb against the G protein of vesicular stomatitis virus--i.e., against an antigen not present in PC12 cells--was expressed as a control. The intracellular localization and the secretion of the antibodies was studied by double-labeling immunofluorescence using the conventional and the confocal microscope, as well as by pulse-chase experiments. The secretogranin I antibody, like the control antibody, was transported along the secretory pathway to the Golgi complex. However, in contrast to the control antibody, which was secreted via the constitutive pathway, the secretogranin I antibody formed an immunocomplex with secretogranin I, was packaged into secretory granules, and was released by regulated exocytosis. Our results show that a constitutive secretory protein, unaltered by genetic engineering, can be diverted to the regulated pathway of secretion by its protein-protein interaction with a regulated secretory protein. The data also provide the basis for immunologically studying the role of luminally exposed protein domains in the biogenesis and function of regulated secretory vesicles.

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Bridging the Gap: Virus Long-Distance Spread via Tunneling Nanotubes

Journal of Virology ◽

10.1128/jvi.02120-19 ◽

2020 ◽

Vol 94 (8) ◽

Cited By ~ 9

Author(s):

Robert J. J. Jansens ◽

Alexander Tishchenko ◽

Herman W. Favoreel

Keyword(s):

Intercellular Communication ◽

Genetic Information ◽

Tunneling Nanotubes ◽

Long Distance ◽

Intercellular Transfer ◽

Current Review ◽

Infected Cells ◽

Molecular Information

ABSTRACT Tunneling nanotubes (TNTs) are actin-based intercellular conduits that connect distant cells and allow intercellular transfer of molecular information, including genetic information, proteins, lipids, and even organelles. Besides providing a means of intercellular communication, TNTs may also be hijacked by pathogens, particularly viruses, to facilitate their spread. Viruses of many different families, including retroviruses, herpesviruses, orthomyxoviruses, and several others have been reported to trigger the formation of TNTs or TNT-like structures in infected cells and use these structures to efficiently spread to uninfected cells. In the current review, we give an overview of the information that is currently available on viruses and TNT-like structures, and we discuss some of the standing questions in this field.

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Intracellular retention of membrane-anchored v-sis protein abrogates autocrine signal transduction.

The Journal of Cell Biology ◽

10.1083/jcb.118.5.1057 ◽

1992 ◽

Vol 118 (5) ◽

pp. 1057-1070 ◽

Cited By ~ 12

Author(s):

B A Lee ◽

D J Donoghue

Keyword(s):

Cell Surface ◽

Secretory Pathway ◽

Transmembrane Protein ◽

Immunofluorescent Localization ◽

Receptor Ligand ◽

Surface Transport ◽

Established Cell ◽

Autocrine Transformation ◽

Nih 3T3 ◽

Retention Signal

An important question regarding autocrine transformation by v-sis is whether intracellularly activated PDGF receptors are sufficient to transform cells or whether activated receptor-ligand complexes are required at the cell surface. We have addressed this question by inhibiting cell surface transport of a membrane-anchored v-sis protein utilizing the ER retention signal of the adenoviral transmembrane protein E3/19K. A v-sis fusion protein containing this signal was retained within the cell and not transported to the cell surface as confirmed by immunofluorescent localization experiments. Also, proteolytic maturation of this protein was suppressed, indicating inefficient transport to post-Golgi compartments of the secretory pathway. When compared with v-sis proteins lacking a functional retention signal, the ER-retained protein showed a diminished ability to transform NIH 3T3 cells, as measured by the number and size of foci formed. In newly established cell lines, the ER-retained protein did not down-regulate PDGF receptors. However, continued passage of these cells selected for a fully transformed phenotype exhibiting downregulated PDGF receptors and proteolytically processed v-sis protein. These results indicate that productive autocrine interactions occur in a post-ER compartment of the secretory pathway. Transport of v-sis protein beyond the Golgi correlated with acquisition of the transformed phenotype. Furthermore, suramin treatment reversed transformation and upregulated the expression of cell surface PDGF receptors, suggesting an important role for receptor-ligand complexes localized to the cell surface.

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