Linked Life Data

1634513

Source:http://linkedlifedata.com/resource/pubmed/id/1634513

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
1992-8-26
pubmed:abstractText
The distribution of heparan sulfate (HS) proteoglycans in clonal rat parathyroid cells is regulated by the extracellular Ca2+ concentration, which is a principal factor for parathyroid cell function (Takeuchi, Y., Sakaguchi, K., Yanagishita, M., Aurbach, G. D., and Hascall, V. C. (1990) J. Biol. Chem. 265, 13661-13668). Increasing the concentration of extracellular Ca2+ in the physiological range redistributes HS proteoglycans from the cell surface to an intracellular compartment. We have now examined effects of the extracellular Ca2+ concentration on the metabolism of the HS proteoglycans in detail using [35S]sulfate metabolic labeling-chase experiments. Two distinct metabolic pathways were demonstrated: (i) the intracellular generation of HS chains from HS proteoglycans in prelysosomal compartments followed by their release into the medium (pathway 1), and (ii) intracellular generation of HS oligosaccharides from HS chains in prelysosomal compartments, which are eventually degraded into free sulfate in lysosomes (pathway 2). The HS oligosaccharides were exclusively present within the cells, whereas HS chains were found primarily in the medium. The cells do not internalize either HS proteoglycans or HS chains from the medium. These observations indicate that these two degradation pathways are independent. In addition to these pathways, approximately 15% of the HS proteoglycans were released into the medium as a proteoglycan form. Treatment of cells with chloroquine, a lysosomotropic agent, did not affect generation of HS chains but inhibited conversion of HS chains to HS oligosaccharides or to free sulfate and resulted in the release of HS chains from the cells. The drug did not affect metabolic pathway 1. The extracellular Ca2+ concentration did not alter these intracellular degradation pathways for HS proteoglycans in the parathyroid cells. Thus, extracellular Ca2+ appears to regulate only the distribution of HS proteoglycans between the cell surface and intracellular compartments, and the process of cycling between these compartments when extracellular Ca2+ is low.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
267
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
14677-84
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Metabolic pathways of heparan sulfate proteoglycans in a rat parathyroid cell line.
pubmed:affiliation
Bone Research Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
pubmed:publicationType
Journal Article