scholarly journals Immunocytochemical Localization of the Prohormone Convertases PC1 and PC2 in Rat Prolactin Cells

1998 ◽  
Vol 46 (1) ◽  
pp. 101-108 ◽  
Author(s):  
Laurent Muller ◽  
Renée Picart ◽  
Alain Barret ◽  
Nabil G. Seidah ◽  
Claude Tougard
Keyword(s):  
Anterior Pituitary ◽  
Biochemical Analysis ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Specific Protein ◽  
Cell Type ◽  
Prolactin Cells ◽  
Prohormone Convertases ◽  
New Information ◽  
Peptide Precursor

The prohormone convertases PC1 and PC2 are subtilisin-related endopepti-dases that process prohormone and neuropeptide precursors. Using different ultrastructural immunocytochemical approaches, we have investigated their intracellular distribution in a neuroendocrine cell type that has not been examined thus far, the rat anterior pituitary lactotrope. These cells secrete mainly prolactin and also express the neuroendocrine-specific protein secretogranin II, which is considered a peptide precursor. Our study provides evidence for the expression of PC1 and PC2 in rat lactotropes and provides new information on their subcellular localization. Apart from their presence in the secretory granules, PC1 and PC2 displayed different major localization along the secretory pathway. PC1 immunoreactivity was concentrated in the Golgi apparatus, whereas PC2 immunoreactivity was prominent in the rough endoplasmic reticulum (RER). These observations provide morphological support for previous biochemical analysis of proPC1 and proPC2 post-translational processing, which has demonstrated that PC1 exits very rapidly from the RER, whereas PC2 is retained much longer in this compartment.

scholarly journals Cell Type-Specific Metabolism of Peptidylglycineα -Amidating Monooxygenase in Anterior Pituitary*

Endocrinology ◽  
2000 ◽  
Vol 141 (8) ◽  
pp. 3020-3034 ◽  
Author(s):  
Rajaa El Meskini ◽  
Richard E. Mains ◽  
Betty A. Eipper
Keyword(s):  
Anterior Pituitary ◽  
Secretory Granules ◽  
Primary Cultures ◽  
Cell Types ◽  
Pituitary Cell ◽  
Male Rat ◽  
Pituitary Cells ◽  
Cell Type ◽  
Cell Content ◽  
Monooxygenase Activity

Peptidylglycine α-amidating monooxygenase (PAM) is a bifunctional enzyme expressed in each major anterior pituitary cell type. We used primary cultures of adult male rat anterior pituitary to examine PAM expression, processing, and secretion in the different pituitary cell types and to compare these patterns to those observed in transfected AtT-20 corticotrope tumor cells. Immunostaining and subcellular fractionation identified PAM in pituitary secretory granules and additional vesicular compartments; in contrast, in AtT-20 cells, transfected PAM was primarily localized to the trans-Golgi network. PAM expression was highest in gonadotropes, with moderate levels in somatotropes and thyrotropes and lower levels in corticotropes and lactotropes. Under basal conditions, less than 1% of the cell content of monooxygenase activity was secreted per h, a rate comparable to the basal rate of release of individual pituitary hormones. General secretagogues stimulated PAM secretion 3- to 5-fold. Stimulation with specific hypothalamic releasing hormones demonstrated that different pituitary cell types secrete characteristic sets of PAM proteins. Gonadotropes and thyrotropes release primarily monofunctional monooxygenase. Somatotropes secrete primarily bifunctional PAM, whereas corticotropes secrete a mixture of mono- and bifunctional proteins. As observed in transfected AtT-20 cells, pituitary cells rapidly internalize the PAM/PAM-antibody complex from the cell surface. The distinctly different steady-state localizations of endogenous PAM in primary pituitary cells and transfected PAM in AtT-20 cell lines may simply reflect the increased storage capacity of primary pituitary cells.

The expression of regulated endocrine-specific protein of 18 kDa in peptidergic cells of rat peripheral endocrine tissues and in blood

1997 ◽  
Vol 155 (2) ◽  
pp. 329-341 ◽  
Author(s):  
DN Darlington ◽  
MR Schiller ◽  
RE Mains ◽  
BA Eipper
Keyword(s):  
Molecular Weight ◽  
Pancreatic Islets ◽  
Adrenal Medulla ◽  
Anterior Pituitary ◽  
Cellular Localization ◽  
Secretory Granules ◽  
Specific Protein ◽  
Intermediate Lobe ◽  
Pituitary Cells ◽  
Endocrine Tissues

We examined the cellular localization of regulated endocrine-specific protein of 18 kDa (RESP18) and mRNA in peripheral endocrine tissues. In situ hybridization and immunocytochemistry identified RESP18 mRNA in most cells of the anterior and intermediate pituitary, with RESP18 protein apparent in many anterior pituitary cells but very few intermediate pituitary cells. In the adrenal medulla and superior cervical ganglion, RESP18 mRNA co-localized with dopamine beta-mono-oxygenase and neuropeptide Y. In the thyroid, RESP18 mRNA was localized to C-cells. RESP18 mRNA was expressed in most of the cells of the pancreatic islets, co-localizing with insulin, glucagon, and somatostatin. No RESP18 mRNA or protein was detected in the adrenal cortex, ovary, neural lobe of the pituitary, parathyroid, exocrine pancreas, thyroid follicular cells, placenta, mammary tissue, liver, lung, or atria. As in the intermediate lobe of the pituitary, high levels of RESP18 mRNA in the pancreatic islets and adrenal medulla did not always correlate with immunodetectable RESP protein, suggesting that post-transcriptional mechanisms are important in controlling RESP18 expression. Western blot analyses identified 18 kDa RESP and higher molecular weight isoforms of RESP in most tissues and in plasma. Subcellular fractionation of the anterior pituitary identified 18 kDa RESP18 in fractions enriched in endoplasmic reticulum and secretory granules, with the higher molecular weight isoforms of RESP18 concentrated in fractions enriched in secretory granules. The broad neuroendocrine distribution of RESP18 suggests that it subserves an important function in the secretory pathway that is common to the production of many secreted peptides.

scholarly journals FURTHER STUDIES ON THE THETA CELL OF THE MOUSE ANTERIOR PITUITARY AS REVEALED BY ELECTRON MICROSCOPY, WITH SPECIAL REFERENCE TO THE MODE OF SECRETION

1962 ◽  
Vol 15 (1) ◽  
pp. 85-97 ◽  
Author(s):  
Masao Sano
Keyword(s):  
Cell Membrane ◽  
Anterior Pituitary ◽  
Amorphous Materials ◽  
Distal Part ◽  
Secretory Granules ◽  
Complete Loss ◽  
Low Density ◽  
Cell Type ◽  
Golgi Vesicles ◽  
Golgi Region

Theta cells reported previously as a new cell type in the anterior pituitary of the mouse were examined with the electron microscope. This type of cell is distinguished by the presence of pleomorphic secretory granules, a characteristic arrangement of the rough surfaced variety of endoplasmic reticulum, a well developed Golgi complex, and an eccentrically located nucleus. The secretory granules are seen at first as small granules of low density within the Golgi vesicles. While they are within the Golgi vesicles they become larger and denser. Simultaneously they move from the proximal to the distal part of the Golgi region and finally emerge from the Golgi area as mature granules in the cytoplasm. Thus, secretory granules are always enveloped by a limiting membrane which originates from the wall of the Golgi vesicle. At the stage of granule-extrusion, the cell membrane fuses with the limiting membrane of the granules and openings in the cell membrane appear at the place of extrusion. The granules then appear to lie within inpocketings of the cell membrane. They lose their density within these inpocketings or within the cytoplasm and occasionally show fragmentation. After complete loss of density, the granules are extruded as amorphous materials to the territory outside of the cell.

AN ELECTRON MICROSCOPIC STUDY OF NORMAL AND NEOPLASTIC ACIDOPHIL CELLS OF THE RAT PITUITARY

1971 ◽  
Vol 67 (1) ◽  
pp. 29-39 ◽  
Author(s):  
U. Schelin ◽  
P. M. Lundin
Keyword(s):  
Electron Microscopy ◽  
Secretory Granules ◽  
Female Rats ◽  
Male Rats ◽  
Cell Type ◽  
Prolactin Cells ◽  
Electron Microscopic ◽  
Gh Cells ◽  
Rat Pituitary ◽  
Close Relationship

ABSTRACT The morphology of normal and neoplastic acidophil cells of the rat pituitary has been studied by electron microscopy with special reference to the size and shape of the secretory granules. In the female rats, pregnant or non-pregnant, growth hormone (GH) cells and prolactin cells are easily separated, but in the male rats this separation is very uncertain. Acidophil tumours with granules similar to the GH type or to the prolactin type can be induced with stilboestrol treatment. These results indicate a close relationship between the two types of acidophil cells. They may be derived from a common progenitor which can be differentiated into either GH or prolactin cell or they may represent one cell type capable of producing both hormones.

scholarly journals The exocrine protein trypsinogen is targeted into the secretory granules of an endocrine cell line: studies by gene transfer.

1985 ◽  
Vol 101 (2) ◽  
pp. 639-645 ◽  
Author(s):  
T L Burgess ◽  
C S Craik ◽  
R B Kelly
Keyword(s):  
Gene Transfer ◽  
Cell Line ◽  
Anterior Pituitary ◽  
Endocrine Cells ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Tumor Cell Line ◽  
Subcellular Fractionation ◽  
Regulated Secretory Pathway ◽  
Stimulation Of

The exocrine protein rat anionic trypsinogen has been expressed and is secreted from the murine anterior pituitary tumor cell line AtT-20. We examined which secretory pathway trypsinogen takes to the surface of this endocrine-derived cell line. The "constitutive" pathway externalizes proteins rapidly and in the absence of an external stimulus. In the alternate, "regulated" pathway, proteins are stored in secretory granules until the cells are stimulated to secrete with 8-Br-cAMP. On the basis of indirect immunofluorescence localization, stimulation of release, and subcellular fractionation, we find that trypsinogen is targeted into the regulated secretory pathway in AtT-20 cells. In contrast, laminin, an endogenous secretory glycoprotein, is shown to be secreted constitutively. Thus it appears that the transport apparatus for the regulated secretory pathway in endocrine cells can recognize not only endocrine prohormones, but also the exocrine protein trypsinogen, which suggests that a similar sorting mechanism is used by endocrine and exocrine cells.

scholarly journals ICA512 RESP18 homology domain is a protein condensing factor and insulin fibrillation inhibitor

2019 ◽  
Author(s):  
Pamela L Toledo ◽  
Juha M Torkko ◽  
Andreas Müller ◽  
Carolin Wegbrod ◽  
Anke Sönmez ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Secretory Granules ◽  
Tyrosine Phosphatase ◽  
Specific Protein ◽  
Terminal Segment ◽  
Extracellular Milieu ◽  
Intrinsically Disordered ◽  
Early Secretory Pathway ◽  
Ph Range

Type 1 diabetes islet cell autoantigen 512 (ICA512) is a tyrosine phosphatase-like intrinsic membrane protein involved in the biogenesis and turnover of insulin secretory granules (SGs) in pancreatic islet β-cells. Whereas its membrane proximal and cytoplasmic domains have been functionally and structurally characterized, the role of ICA512 N-terminal segment named regulated endocrine-specific protein 18 homology domain (RESP18HD), which encompasses residues 35-131, remains largely unknown. Here we show that ICA512 RESP18HD residues 91-131 encode for an intrinsically disordered region (IDR), which in vitro acts as a condensing factor for the reversible aggregation of insulin and other β-cell proteins in a pH and Zn2+ regulated fashion. At variance with what has been shown for other granule cargoes with aggregating properties, the condensing activity of ICA512 RESP18HD is displayed at pH close to neutral, i.e. in the pH range found in the early secretory pathway, while it is resolved at acidic pH and Zn2+ concentrations resembling those present in mature SGs. Moreover, we show that ICA512 RESP18HD residues 35-90, preceding the IDR, inhibit insulin fibrillation in vitro. Finally, we found that glucose-stimulated secretion of RESP18HD upon exocytosis of SGs from insulinoma INS-1 cells is associated with cleavage of its IDR, conceivably to prevent its aggregation upon exposure to neutral pH in the extracellular milieu. Taken together, these findings point to ICA512 RESP18HD being a condensing factor for protein sorting and granulogenesis early in the secretory pathway, and for prevention of amyloidogenesis.

Disruption of disulfide bonds exhibits differential effects on trafficking of regulated secretory proteins

1999 ◽  
Vol 277 (1) ◽  
pp. C121-C131 ◽  
Author(s):  
Sven-Ulrik Gorr ◽  
Xue Fen Huang ◽  
Darrin J. Cowley ◽  
Regina Kuliawat ◽  
Peter Arvan
Keyword(s):  
Pancreatic Islets ◽  
Disulfide Bond ◽  
Protein Trafficking ◽  
Disulfide Bonds ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Secretory Proteins ◽  
Cell Type ◽  
Chromogranin B ◽  
Disulfide Reduction

For several secretory proteins, it has been hypothesized that disulfide-bonded loop structures are required for sorting to secretory granules. To explore this hypothesis, we employed dithiothreitol (DTT) treatment in live pancreatic islets, as well as in PC-12 and GH4C1cells. In islets, disulfide reduction in the distal secretory pathway did not increase constitutive or constitutive-like secretion of proinsulin (or insulin). In PC-12 cells, DTT treatment caused a dramatic increase in unstimulated secretion of newly synthesized chromogranin B (CgB), presumably as a consequence of reducing the single conserved chromogranin disulfide bond (E. Chanat, U. Weiss, W. B. Huttner, and S. A. Tooze. EMBO J.12: 2159–2168, 1993). However, in GH4C1cells that also synthesize CgB endogenously, DTT treatment reduced newly synthesized prolactin and blocked its export, whereas newly synthesized CgB was routed normally to secretory granules. Moreover, on transient expression in GH4C1cells, CgA and a CgA mutant lacking the conserved disulfide bond showed comparable multimeric aggregation properties and targeting to secretory granules, as measured by stimulated secretion assays. Thus the conformational perturbation of regulated secretory proteins caused by disulfide disruption leads to consequences in protein trafficking that are both protein and cell type dependent.

scholarly journals Angiotensinogen, Prorenin, and Renin Are Co-localized in the Secretory Granules of All Glandular Cells of the Rat Anterior Pituitary: An Immunoultrastructural Study

1998 ◽  
Vol 46 (3) ◽  
pp. 301-311 ◽  
Author(s):  
Evelyne Vila-Porcile ◽  
Pierre Corvol
Keyword(s):  
Anterior Pituitary ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Mammalian Species ◽  
Simultaneous Detection ◽  
Renin Angiotensin System ◽  
Cell Types ◽  
Local System ◽  
Glandular Cell ◽  
Glandular Cells

In addition to the circulating renin–angiotensin system (RAS), a local system has been postulated in the anterior pituitary because immunodetection of its components in various mammalian species. However, different cell types appear to be involved in different species, and there is no general consensus on the subcellular localization of prorenin, renin and angiotensinogen. In this ultrastructural study, we investigated and quantified the presence of these components using double or triple immunogold labeling methods, in all the immunologically identified glandular cell types of the rat anterior pituitary. In contrast to previous reports, all these components were identified not only in lactotropes and gonadotropes but also in somatotropes, corticotropes, and thyrotropes. The highest levels were detected in lactotropes and gonadotropes, and renin gave the greatest signal. Angio-tensinogen, prorenin, and renin were co-localized in the secretory granules of all rat pituitary glandular cell types. The simultaneous detection of the substrate (angiotensinogen) and both its specific cleavage enzyme and its proenzyme within the same granule suggests intragranular processing of this component. Moreover, the localization of these three constituents in the secretory granules also suggests that, in the rat anterior pituitary, they follow the regulated secretory pathway.

Sign in / Sign up

Export Citation Format

Share Document