The Regulated Secretory Pathway in Neuroendocrine Cells

Golgi-associated long coiled-coil proteins, often referred to as golgins, are involved in the maintenance of the structural organization of the Golgi apparatus and the regulation of membrane traffic events occurring in this organelle. Little information is available on the contribution of golgins to Golgi function in cells specialized in secretion such as endocrine cells or neurons. In the present study, we characterize the intracellular distribution as well as the biochemical and functional properties of a novel long coiled-coil protein present in neuroendocrine tissues, NECC1 (neuroendocrine long coiled-coil protein 1). The present study shows that NECC1 is a peripheral membrane protein displaying high stability to detergent extraction, which distributes across the Golgi apparatus in neuroendocrine cells. In addition, NECC1 partially localizes to post-Golgi carriers containing secretory cargo in PC12 cells. Overexpression of NECC1 resulted in the formation of juxtanuclear aggregates together with a slight fragmentation of the Golgi and a decrease in K+-stimulated hormone release. In contrast, NECC1 silencing did not alter Golgi architecture, but enhanced K+-stimulated hormone secretion in PC12 cells. In all, the results of the present study identify NECC1 as a novel component of the Golgi matrix and support a role for this protein as a negative modulator of the regulated trafficking of secretory cargo in neuroendocrine cells.

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Secretory Granule Biogenesis and Neuropeptide Sorting to the Regulated Secretory Pathway in Neuroendocrine Cells

Journal of Molecular Neuroscience ◽

10.1385/jmn:22:1-2:63 ◽

2004 ◽

Vol 22 (1-2) ◽

pp. 63-72 ◽

Cited By ~ 37

Author(s):

Y. Peng Loh ◽

Taeyoon Kim ◽

Yazmin M. Rodriguez ◽

Niamh X. Cawley

Keyword(s):

Secretory Granule ◽

Secretory Pathway ◽

Neuroendocrine Cells ◽

Regulated Secretory Pathway

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Corticotropin-releasing factor binding protein enters the regulated secretory pathway in neuroendocrine cells and cortical neurons

Neuropeptides ◽

10.1016/j.npep.2011.05.002 ◽

2011 ◽

Vol 45 (4) ◽

pp. 273-279 ◽

Cited By ~ 12

Author(s):

Elías H. Blanco ◽

Juan Pablo Zúñiga ◽

María Estela Andrés ◽

Alejandra R. Alvarez ◽

Katia Gysling

Keyword(s):

Cortical Neurons ◽

Secretory Pathway ◽

Binding Protein ◽

Corticotropin Releasing Factor ◽

Neuroendocrine Cells ◽

Factor Binding ◽

Regulated Secretory Pathway

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Basic mechanisms of secretion: sorting into the regulated secretory pathway

Biochemistry and Cell Biology ◽

10.1139/o00-010 ◽

2000 ◽

Vol 78 (3) ◽

pp. 181-191 ◽

Cited By ~ 29

Author(s):

Mercedes Blázquez ◽

Kathleen I Shennan

Keyword(s):

Secretory Pathway ◽

Biological Function ◽

Neuroendocrine Cells ◽

Secretory Pathways ◽

Lipid Interactions ◽

Trans Golgi Network ◽

Sorting Signals ◽

Sorting Process ◽

Regulated Secretory Pathway ◽

Golgi Network

Targeting proteins to their correct cellular location is crucial for their biological function. In neuroendocrine cells, proteins can be secreted by either the constitutive or the regulated secretory pathways but the mechanism(s) whereby proteins are sorted into either pathway is unclear. In this review we discuss the possibility that sorting is either an active process occurring at the level of the trans-Golgi network, or that sorting occurs passively in the immature granules. The possible involvement of protein-lipid interactions in the sorting process is also raised. Key words: lipid rafts, regulated secretory pathway, secretion, sorting receptors, sorting signals, trans-Golgi network.

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COOH-terminal signals mediate the trafficking of a peptide processing enzyme in endocrine cells.

The Journal of Cell Biology ◽

10.1083/jcb.121.1.23 ◽

1993 ◽

Vol 121 (1) ◽

pp. 23-36 ◽

Cited By ~ 50

Author(s):

S L Milgram ◽

R E Mains ◽

B A Eipper

Keyword(s):

Plasma Membrane ◽

Cell Surface ◽

Endocrine Cells ◽

Secretory Pathway ◽

Bioactive Peptides ◽

Full Length ◽

Neuroendocrine Cells ◽

Subcellular Compartment ◽

Peptide Processing ◽

Regulated Secretory Pathway

Peptidylglycine alpha-amidating monooxygenase (PAM) catalyzes the COOH-terminal amidation of bioactive peptides through a two step reaction catalyzed by separate enzymes contained within the PAM precursor. To characterize the trafficking of integral membrane PAM proteins in neuroendocrine cells, we have generated stable AtT-20 cell lines expressing full length and COOH-terminally truncated integral membrane PAM proteins. Full length integral membrane PAM was present on the cell surface in low but detectable amounts and PAM proteins which reached the cell surface were rapidly internalized but not immediately degraded in lysosomes. Internalized PAM complexed with PAM antibody was found in a subcellular compartment which overlapped with internalized transferrin and with structures binding WGA. Thus the punctate juxtanuclear staining of full length PAM represents PAM in endosomes. Endoproteolytic processing of full length PAM-1 and PAM-2 resulted in the secretion of soluble PAM proteins; the secretion of these soluble PAM proteins was stimulus dependent. Although some of the truncated PAM protein was also processed and stored in AtT-20 cells, much of the expressed protein was redistributed to the plasma membrane. Soluble proteins not observed in large amounts in cells expressing full length PAM were released from the surface of cells expressing truncated PAM and little internalization of truncated integral membrane PAM was observed. Thus, the COOH-terminal domain of PAM contains information important for its trafficking within the regulated secretory pathway as well as information necessary for its retrieval from the cell surface.

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Prohormone transport through the secretory pathway of neuroendocrine cells

Biochemistry and Cell Biology ◽

10.1139/o00-020 ◽

2000 ◽

Vol 78 (3) ◽

pp. 289-298 ◽

Cited By ~ 12

Author(s):

Roland P Kuiper ◽

Gerard JM Martens

Keyword(s):

Secretory Pathway ◽

Potential Role ◽

Protein Transport ◽

Secretory Granules ◽

Secretory Protein ◽

Neuroendocrine Cells ◽

Secretory Proteins ◽

Regulated Secretory Pathway ◽

Made In

En route through the secretory pathway of neuroendocrine cells, prohormones pass a series of membrane-bounded compartments. During this transport, the prohormones are sorted to secretory granules and proteolytically cleaved to bioactive peptides. Recently, progress has been made in a number of aspects concerning secretory protein transport and sorting, particularly with respect to transport events in the early regions of the secretory pathway. In this review we will deal with some of these aspects, including: i) selective exit from the endoplasmic reticulum via COPII-coated vesicles and the potential role of p24 putative cargo receptors in this process, ii) cisternal maturation as an alternative model for protein transport through the Golgi complex, and iii) the mechanisms that may be involved in the sorting of regulated secretory proteins to secretory granules. Although much remains to be learned, interesting new insights into the functioning of the secretory pathway have been obtained.Key words: regulated secretory pathway, p24 family, vesicular transport, POMC, protein sorting, secretory granule, Xenopus laevis.

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Discovery and progress in our understanding of the regulated secretory pathway in neuroendocrine cells

Histochemistry and Cell Biology ◽

10.1007/s00418-008-0377-z ◽

2008 ◽

Vol 129 (3) ◽

pp. 243-252 ◽

Cited By ~ 45

Author(s):

Joëlle Morvan ◽

Sharon A. Tooze

Keyword(s):

Secretory Pathway ◽

Neuroendocrine Cells ◽

Regulated Secretory Pathway

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RNAi screen identifies a role for adaptor protein AP-3 in sorting to the regulated secretory pathway

The Journal of Cell Biology ◽

10.1083/jcb.201006131 ◽

2010 ◽

Vol 191 (6) ◽

pp. 1173-1187 ◽

Cited By ~ 45

Author(s):

Cédric S. Asensio ◽

Daniel W. Sirkis ◽

Robert H. Edwards

Keyword(s):

Secretory Pathway ◽

Adaptor Protein ◽

Neuroendocrine Cells ◽

Endocytic Pathway ◽

Dense Core ◽

Primary Defect ◽

Regulated Exocytosis ◽

Drosophila Melanogaster S2 Cells ◽

Large Dense Core Vesicles ◽

Regulated Secretory Pathway

The regulated release of proteins depends on their inclusion within large dense-core vesicles (LDCVs) capable of regulated exocytosis. LDCVs form at the trans-Golgi network (TGN), but the mechanism for protein sorting to this regulated secretory pathway (RSP) and the cytosolic machinery involved in this process have remained poorly understood. Using an RNA interference screen in Drosophila melanogaster S2 cells, we now identify a small number of genes, including several subunits of the heterotetrameric adaptor protein AP-3, which are required for sorting to the RSP. In mammalian neuroendocrine cells, loss of AP-3 dysregulates exocytosis due to a primary defect in LDCV formation. Previous work implicated AP-3 in the endocytic pathway, but we find that AP-3 promotes sorting to the RSP within the biosynthetic pathway at the level of the TGN. Although vesicles with a dense core still form in the absence of AP-3, they contain substantially less synaptotagmin 1, indicating that AP-3 concentrates the proteins required for regulated exocytosis.

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