Switch to
| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
16
|
| pubmed:dateCreated |
1984-9-28
|
| pubmed:abstractText |
The metabolism of endogenously labeled proteoglycans was studied in rat ovarian granulosa cell cultures by a series of pulse-chase experiments using [35S]sulfate as a precursor. More than 90% of the newly synthesized proteoglycans are transported to the cell surface (trypsin-accessible compartment) with a median transit time of 13 min. The membrane-bound heparan sulfate-proteoglycan (HS-PG) is lost from the cell surface either by release into the medium (30%, with t1/2 of 4 h) or by internalization (70%, with t1/2 of 4 h). Internalized HS-PG, which does not recycle to the cell surface, is degraded by two major pathways. In pathway 1, 60% of the internalized HS-PG migrates to lysosomes with a relatively short t1/2 of 30 min, where it is rapidly degraded, releasing free [35S]sulfate without detectable intermediate products. Chloroquine treatment inhibited degradation, resulting in the accumulation of intact proteoglycans inside the cell. In pathway 2, 40% of the internalized HS-PG is first subjected to extensive proteolysis and limited endoglycosidic degradation yielding single HS chains about 1/3 of their original size (t1/2 of 30 min). Chloroquine did not inhibit this step. The partially degraded HS is then degraded further by limited endoglycosidic activity to about 1/4-1/5 the original size (t1/2 of 30-60 min). This step is inhibited by chloroquine. These smaller fragments have a relatively long t1/2 of 3-4 h before rapid degradation in the lysosomes, releasing free [35S]sulfate. Approximately 7% of the newly synthesized HS-PG that is not transported to the cell surface is degraded directly by pathway 2. The larger dermatan sulfate proteoglycan (DS-I) is transported to the cell surface from which it is quantitatively released into the medium with a t1/2 of 4-6 h. The smaller DS-PG (DS-II) is metabolized similarly to the HS-PG. Most (greater than 90%) is transported to the cell surface from which it is lost either by release into the medium (40%) or by internalization (60%). About 60% of the internalized DS-II is degraded by pathway 1 (t1/2 of 30 min), while the remainder appears to be degraded by pathway 2 with an overall t1/2 of 4 h. However, in contrast to the degradation of HS-PG by pathway 2, no endoglycosidic degradation of the DS chains occurred.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Aug
|
| pubmed:issn |
0021-9258
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
25
|
| pubmed:volume |
259
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
10270-83
|
| pubmed:dateRevised |
2003-11-14
|
| pubmed:meshHeading |
pubmed-meshheading:6469965-Animals,
pubmed-meshheading:6469965-Biological Transport,
pubmed-meshheading:6469965-Cells, Cultured,
pubmed-meshheading:6469965-Chloroquine,
pubmed-meshheading:6469965-Female,
pubmed-meshheading:6469965-Granulosa Cells,
pubmed-meshheading:6469965-Kinetics,
pubmed-meshheading:6469965-Models, Biological,
pubmed-meshheading:6469965-Proteoglycans,
pubmed-meshheading:6469965-Rats,
pubmed-meshheading:6469965-Sulfates,
pubmed-meshheading:6469965-Sulfur Radioisotopes,
pubmed-meshheading:6469965-Time Factors
|
| pubmed:year |
1984
|
| pubmed:articleTitle |
Metabolism of proteoglycans in rat ovarian granulosa cell culture. Multiple intracellular degradative pathways and the effect of chloroquine.
|
| pubmed:publicationType |
Journal Article
|