Linked Life Data

2948961

Source:http://linkedlifedata.com/resource/pubmed/id/2948961

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1987-3-23
pubmed:abstractText
The metabolism of heparan sulfate proteoglycan, a major product of human colon carcinoma cells, was investigated in a series of pulse-chase experiments using a combination of quantitative biochemistry and electron microscope autoradiography. This was possible primarily because these cells incorporate [35S]sulfate exclusively into heparan sulfate proteoglycan, thus allowing the possibility of correlating the two sets of information. The results showed a progressive movement of the newly synthesized proteoglycan from the Golgi to the cell surface, where it became closely associated with the plasma membrane and was labeled ultrastructurally by both ruthenium red and radiosulfate. Subsequently, about 55% was released into the medium (t1/2 approximately 2.5 h) where it resided as intact macromolecule and was neither endocytosed nor degraded further. The remaining 45% was internalized and converted into smaller species through a series of degradative steps. Initially (Step 1) there was proteolytic cleavage of the protein core and partial endoglycosidic cleavage of the heparan sulfate chains (t1/2 approximately 6 h), with generation of larger glycosaminoglycan-peptide intermediates with chains of Mr approximately 10,000, about one-third their original size. These components were subsequently converted (Step 2) to yet smaller, limiting fragments of Mr approximately 5,000, which were finally depolymerized (Step 3) with quantitative release of free sulfate. The intracellular degradation of the proteoglycan, particularly Steps 2 and 3, was markedly inhibited by choloroquine, implicating the involvement of acidic compartments in the catabolism of these macromolecules. This was corroborated by the autoradiographic studies which showed the close association of 35S-labeled products with secondary lysosomes. However, the initial degradation of the proteoglycan might have occurred in a prelysosomal compartment since Step 1 was not totally blocked by chloroquine. The combined results indicate that the intracellular degradation of heparan sulfate follows structural as well as functional compartmentalization and provide a model that may be shared by other cell systems.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
262
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1888-900
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
1987
pubmed:articleTitle
Turnover of heparan sulfate proteoglycan in human colon carcinoma cells. A quantitative biochemical and autoradiographic study.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't