Complex Carbohydrates of Secretory Organelles

Giannattasio, G.; Zanini, A.; Meldolesi, Jacopo

doi:10.1007/978-1-4613-2925-1_15

Cited by 9 publications

(2 citation statements)

References 77 publications

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“…It seems interesting that also in the other protein-secreting granule type so far analyzed, the zymogen granule of the pancreas, the concentration of sulfated carbohydrates was found to be very low (22) . The different situation reported for complex carbohydrates in chromaffm granules of the adrenal medulla might be only apparent because in this system two glycoproteins, chromogranin A and dopamine-a-hydroxylase, are the major macromolecular secretion products (6,10). The low concentrations of complex carbohydrates found in PRL granules seem incompatible with the idea previously proposed (9) that in these organelles the insolubilization of the matrix is caused by the direct binding of all hormone molecules to the negatively charged residues of glycosylated polyanions.…”

Section: Distribution Of Glycoproteins In Subcellular Fractions Isolated From Bovine Pituitarymentioning

confidence: 93%

Molecular organization of prolactin granules. II. Characterization of glycosaminoglycans and glycoproteins of the bovine prolactin matrix.

Zanini¹,

Giannattasio²,

Gg³

et al. 1980

The Journal of Cell Biology

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Prolactin (PRL) granules can be isolated from the anterior pituitary gland of adult cows in nearly 50% yield by use of a procedure previously developed for the fractionation of the rat pituitary. Treatment of the isolated bovine granules with 0.2% Lubrol PX results in the solubilization of most membranes present in the fraction but has only a limited effect on the matrices, which remain aggregated and can be recovered and purified by gradient centrifugation . These membraneless PRL granules, studied in detail by morphological and biochemical techniques, were found to contain only small amounts of contaminants (primarily growth hormone granules and small membrane fragments) . SIDS polyacrylamide gel electrophoresis revealed that, in comparison with other fractions isolated from the bovine pituitary, the membraneless granules have a simpler polypeptide composition including PRL (-85%), growth hormone (-8%), as well as ---13 minor bands with apparent mol wt ranging from 80,000 to 45,000 . Many of these minor bands are accounted for by glycoproteins, as revealed by their binding of ' 25 1-concanavalin A, and two of these are also stained blue by the stains-all procedure, a reaction specific for acidic glycoconjugates. Chemical analyses of the membraneless granule fraction revealed the presence of a heterogeneous mixture of complex carbohydrates . Among glycosaminoglycans, the major component is heparan sulfate, while hyaluronic acid and chondroitin sulfate are present in smaller amounts. Moreover, some of the glycoproteins are sulfated and account for over 50% of the nondialyzable "S radioactivity found in the fraction isolated from labeled slices . Although the concentration of glycosaminoglycans and glycoproteins is relatively low in membraneless granules, the possibility that their presence in the fraction is largely due to cross-contamination and/or artifactual adsorption could be excluded on two grounds. These are: (a) electron microscope radioautography of preparations obtained from ["S]sulfate-and D-[6-3H]glucosamine-labeled slices showed a significant labeling of PRL granules in both intact cells and membraneless granule pellets, and (b) a mixing experiment showed that membraneless granules contain very little macromolecular sulfate radioactivity adsorbed from the soluble glycoconjugates present in the pituitary homogenate .Experimental evidence obtained during the last several years clearly indicates that macromolecular carbohydrates are components of secretory granules not only in cell systems which are specialized for their secretion, but also in many others whose main exported products are of a different nature (e .g., amines and nonglycosylated proteins and peptides) (l0, 19). The function of these minor components is still poorly defined. 260Recently, however, there has been considerable interest in these macromolecules since it has been proposed that they might be involved in the packaging of secretion products (21) . This process, which occurs in the Golgi complex, results in the organizatio...

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Section: Distribution Of Glycoproteins In Subcellular Fractions Isolated From Bovine Pituitarymentioning

confidence: 93%

Molecular organization of prolactin granules. II. Characterization of glycosaminoglycans and glycoproteins of the bovine prolactin matrix.

Zanini¹,

Giannattasio²,

Gg³

et al. 1980

The Journal of Cell Biology

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“…In other endocrine and transmitter-storing tissues, the presence of secretory proteoglycans has also been established (see Giannattasio et al, 1979).…”

Section: I479mentioning

confidence: 99%

Biogenesis of Chromaffin Granules: Incorporation of Sulfate into Chromogranin B and into a Proteoglycan

Falkensammer

Fischer‐Colbrie

Winkler

1985

Journal of Neurochemistry

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The incorporation of [35S]sulfate into the soluble proteins of chromaffin granules was studied. Isolated bovine chromaffin cells were pulse-labeled with [35S]sulfate. The radioactively labeled products were characterized by one- and two-dimensional electrophoresis. Three proteins of chromaffin granules were preferentially labeled. One was identified by immunoprecipitation as chromogranin B (Mr 100,000). This result explains why during cellular synthesis the chromogranin B precursor is converted into a significantly more acidic protein. During chase periods, the newly synthesized chromogranin B was progressively degraded by endogenous proteases. A second labeled protein, much less labeled than chromogranin B, was identified as chromogranin A. The largest portion of the radioactive label was found in a heterogeneous component (Mr 86,000-100,000; pI 4.3-5.0). Digestion experiments with chondroitinase ABC demonstrated that this labeled component and a comigrating Coomassie Blue-stained spot were selectively degraded by this enzyme. This establishes that this component is a proteoglycan.

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Nervous System Glycoproteins

Kelly

1984

The Biology of Glycoproteins

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Complex Carbohydrates of Secretory Organelles

Cited by 9 publications

References 77 publications

Molecular organization of prolactin granules. II. Characterization of glycosaminoglycans and glycoproteins of the bovine prolactin matrix.

Molecular organization of prolactin granules. II. Characterization of glycosaminoglycans and glycoproteins of the bovine prolactin matrix.

Biogenesis of Chromaffin Granules: Incorporation of Sulfate into Chromogranin B and into a Proteoglycan

Nervous System Glycoproteins

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