Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Incomplete posttranslational prohormone modifications in hyperactive neuroendocrine cells.
Strating JR
,
Martens GJ
.
???displayArticle.abstract???
In black-background-adapted Xenopus laevis, the intermediate pituitarymelanotrope cells are hyperactive, producing large amounts of their major secretory cargo proopiomelanocortin (POMC, representing ~80% of all newly synthesised proteins), whereas in white-adapted frogs these cells are only basally active. Here we explored in the hyperactive and basally active melanotrope cells the capacity for posttranslational POMC processing events in the secretory pathway. We found that the hyperactive cells produced mainly non-complex N-glycosylated POMC, whereas in the basally active cells POMC was mostly complex N-glycosylated. Furthermore, the relative level of POMC sulphation was ~5.5-fold lower in the hyperactive than in the basally active cells. When the cargo load in the secretory pathway of the hyperactive cells was pharmacologically reduced, the relative amount of complex glycosylated POMC markedly increased. Collectively, our data show that the secretory pathway in hyperactive neuroendocrine secretory cells lacks the capacity to fully comply with the high demands for complex glycosylation and sulphation of the overload of secretory cargo. Thus, a hyperactive secretory cell may run short in providing an output of correctly modified biological signals.
Figure 1. Biosynthesis of POMC in hyperactive and basally active Xenopus melanotrope cells. A, Neurointermediate lobes (NILs) from black-adapted (BA) and white-adapted (WA) animals were pulse labelled with [35S]methionine/cysteine for 30 minutes and subsequently chased for three hours. The WA NILs were pulsed and chased in the presence of 10-6 M apomorphine to retain their basally active characteristics. Aliquots of the cell lysates (cells; BA: 5% of total lysate, WA: 10%) and the incubation media (media; BA: 10%, WA: 20%) were analysed by 15% SDS-PAGE and autoradiography. B, The amount of 37 K POMC remaining in the cells following the pulse-chase incubation. C, The total amounts (cells + media) of 18 K and 18 K* POMC produced during the pulse-chase incubations. The 18 K*/18 K ratios are given above the bars. Data are shown as means +/- s.e.m.; **, p < 0.01; all bars represent four animals.
Figure 2. Dynamics of 18 K and 18 K* POMC biosynthesis in hyperactive Xenopus melanotrope cells. Neurointermediate lobes from black-adapted Xenopus laevis were pulse labelled with [35S]methionine/cysteine for ten minutes and chased for the indicated time periods. Aliquots of the cell lysates (10%) and the incubation media (20%) were analysed by 15% SDS-PAGE and autoradiography.
Figure 3. Glycosylation and sulphation of POMC in hyperactive and basally active Xenopus melanotrope cells. A, Neurointermediate lobes (NILs) from black-adapted (BA) and white-adapted (WA) animals were pulse labelled with [35S]methionine/cysteine for 60 minutes and chased for two hours. The WA NILs were pulsed and chased in the presence of 10-6 M apomorphine to retain their basally active characteristics. NIL proteins were control treated (C) or deglycosylated with Peptidyl N-glycosidase F (PNGaseF; F) or Endoglycosidase H (EndoH; H), and subsequently analysed by SDS-PAGE and autoradiography. B, Newly synthesised proteins in NILs from BA (n = 12) and WA (n = 4) animals were double-labelled with [3H]lysine and [35S]sulphate for 15 minutes. The WA NIL proteins were labelled in the presence of 10-6 M apomorphine. NIL proteins (40% of the cell lysate) were separated by 12.5% SDS-PAGE and the relative amount of each label incorporated in newly synthesised 37 K POMC was determined. C, NIL proteins from BA and WA animals were labelled as in B, control treated (C) or deglycosylated with PNGaseF (F) or EndoH (H), and analysed by 12.5% SDS-PAGE and autoradiography. Data are shown as means +/- s.e.m.; **, p < 0.01.
Figure 4. Glycosylation of POMC in cycloheximide-treated melanotrope cells from black-adapted Xenopus. A, Neurointermediate lobes (NILs) from black-adapted Xenopus were pre-incubated, pulse labelled with [35S]methionine/cysteine for 30 minutes and chased for three hours in the absence (control) or presence of cycloheximide (Cyclohex.; drug concentrations indicated above the lanes). Since for the samples of the cycloheximide-treated NILs the intensities of the autoradiographic signals were relatively low, a larger part of the cycloheximide-treated NIL lysates than of the untreated NIL lysates was loaded (indicated below the lanes). The slightly reduced mobility of 37 K POMC in the sample treated with 1 μg/ml cycloheximide was due to a gel problem. B, NILs from black-adapted Xenopus were pre-incubated, pulsed and chased as in panel A in the absence or presence of the indicated concentration of cycloheximide. Aliquots (10%) of the lysates were control-treated (C) or deglycosylated with Peptidyl N-glycosidase F (PNGaseF; F) or Endoglycosidase H (EndoH; H), and analysed by SDS-PAGE and autoradiography. To compensate for the reduced labelling in the presence of cycloheximide, the right panel was exposed twice as long as the left panel.
Barrios-De-Tomasi,
Assessment of the in vitro and in vivo biological activities of the human follicle-stimulating isohormones.
2002, Pubmed
Barrios-De-Tomasi,
Assessment of the in vitro and in vivo biological activities of the human follicle-stimulating isohormones.
2002,
Pubmed
Bateman,
Post-translational modification of bovine pro-opiomelanocortin. Tyrosine sulfation and pyroglutamate formation, a mass spectrometric study.
1990,
Pubmed
Berghs,
The secretory granule and pro-opiomelanocortin processing in Xenopus melanotrope cells during background adaptation.
1997,
Pubmed
,
Xenbase
Bodanszky,
Cholecystokinin (pancreozymin). 4. Synthesis and properties of a biologically active analogue of the C-terminal heptapeptide with epsilon-hydroxynorleucine sulfate replacing tyrosine sulfate.
1978,
Pubmed
Bourbonnais,
Posttranslational modifications of proopiomelanocortin in rat intermediate lobe cells.
1986,
Pubmed
Bouw,
A cell-specific transgenic approach in Xenopus reveals the importance of a functional p24 system for a secretory cell.
2004,
Pubmed
,
Xenbase
Budarf,
Effect of tunicamycin on the synthesis, processing, and secretion of pro-opiomelanocortin peptides in mouse pituitary cells.
1982,
Pubmed
Colvin,
CXCR3 requires tyrosine sulfation for ligand binding and a second extracellular loop arginine residue for ligand-induced chemotaxis.
2006,
Pubmed
Daniels,
Sweet 'n' sour: the impact of differential glycosylation on T cell responses.
2002,
Pubmed
Fares,
The role of O-linked and N-linked oligosaccharides on the structure-function of glycoprotein hormones: development of agonists and antagonists.
2006,
Pubmed
Haines,
Glycosylation regulates Notch signalling.
2003,
Pubmed
Haro,
Glycosylated human prolactin: alterations in glycosylation pattern modify affinity for lactogen receptor and values in prolactin radioimmunoassay.
1990,
Pubmed
Jenks,
The functional significance of glycosylation of pro-opiomelanocortin in melanotrophs of the mouse pituitary gland.
1985,
Pubmed
Jensen,
Secretory effects of gastrins on isolated perfused porcine pancreas.
1980,
Pubmed
Kehoe,
Tyrosine sulfation: a modulator of extracellular protein-protein interactions.
2000,
Pubmed
Kuiper,
Prohormone transport through the secretory pathway of neuroendocrine cells.
2000,
Pubmed
,
Xenbase
Loh,
The role of the carbohydrate in the stabilization, processing, and packaging of the glycosylated adrenocorticotropin-endorphin common precursor in toad pituitaries.
1979,
Pubmed
,
Xenbase
Loh,
Evidence that glycosylation of pro-opiocortin and ACTH influences their proteolysis by trypsin and blood proteases.
1980,
Pubmed
,
Xenbase
Loh,
The role of glycosylation on the biosynthesis, degradation, and secretion of the ACTH-beta-lipotropin common precursor and its peptide products.
1978,
Pubmed
,
Xenbase
Lu,
Isolation and structure-bioactivity characterization of glycosylated N-pro-opiomelanocortin isoforms.
2002,
Pubmed
Markoff,
Glycosylation selectively alters the biological activity of prolactin.
1988,
Pubmed
Martens,
Expression of two proopiomelanocortin genes in the pituitary gland of Xenopus laevis: complete structures of the two preprohormones.
1986,
Pubmed
,
Xenbase
Martens,
Biosynthesis of two structurally different pro-opiomelanocortins in the pars intermedia of the amphibian pituitary gland.
1982,
Pubmed
,
Xenbase
Martens,
Biosynthesis of pairs of peptides related to melanotropin, corticotropin and endorphin in the pars intermedia of the amphibian pituitary gland.
1982,
Pubmed
,
Xenbase
Monigatti,
The Sulfinator: predicting tyrosine sulfation sites in protein sequences.
2002,
Pubmed
Seger,
Structure and bioactivity of the amino-terminal fragment of pro-opiomelanocortin.
1986,
Pubmed
Simpson,
Regulation of chemokine recognition by site-specific tyrosine sulfation of receptor peptides.
2009,
Pubmed
Sinha,
Isolation and biochemical properties of four forms of glycosylated porcine prolactin.
1991,
Pubmed
Strating,
Disparate effects of p24alpha and p24delta on secretory protein transport and processing.
2007,
Pubmed
,
Xenbase
Strating,
Functional diversity among p24 subfamily members.
2009,
Pubmed
,
Xenbase
Unsworth,
O-sulphated Leu-enkephalin in brain.
1982,
Pubmed
van Anken,
Sequential waves of functionally related proteins are expressed when B cells prepare for antibody secretion.
2003,
Pubmed
van Anken,
Endoplasmic reticulum stress and the making of a professional secretory cell.
2005,
Pubmed
van Kuppeveld,
Intracellular transport, sorting, and proteolytic processing of regulated secretory proteins does not require protein sulfation.
1997,
Pubmed
,
Xenbase
van Strien,
Biosynthesis and processing of the N-terminal part of proopiomelanocortin in Xenopus laevis: characterization of gamma-MSH peptides.
1995,
Pubmed
,
Xenbase
Vaudry,
Effect of tunicamycin on biosynthesis, processing and release of proopiomelanocortin-derived peptides in the intermediate lobe of the frog Rana ridibunda.
1986,
Pubmed
Verburg-Van Kemenade,
GABA and dopamine act directly on melanotropes of Xenopus to inhibit MSH secretion.
1986,
Pubmed
,
Xenbase
