Binding, internalization, and degradation of antiproliferative heparan sulfate by human embryonic lung fibroblasts

Research output: Contribution to journalArticle

Abstract

Binding, internalization, and degradation of 125I-labeled, antiproliferative, or nonantiproliferative heparan sulfate by human embryonic lung fibroblasts was investigated. Both L-iduronate-rich, antiproliferative heparan sulfate species as well as L-iduronate-poor, inactive ones were bound to trypsin-releasable, cell-surface sites. Both heparan sulfate types were bound with approximately the same affinity to one high-affinity site (Kd approximately 10(-8) M) and to one low-affinity site (Kd approximately 10(-6) M), respectively. Results of Hill-plot analysis suggested that the two sites are independent. Competition experiments with unlabeled glycosaminoglycans indicated that the binding sites had a selective specificity for sulfated, L-iduronate-rich heparan sulfate. Dermatan sulfate, which is also antiproliferative, was weakly bound to the cells. The antiproliferative effects of heparan and dermatan sulfate appeared to be additive. Hence, the two glycosaminoglycans probably exert their effect through different mechanisms. At concentrations above 5 micrograms/ml (approximately 10(-7) M), heparan sulfate was taken up by human embryonic lung fibroblasts, suggesting that the low-affinity site represents an endocytosis receptor. The antiproliferative effect of L-iduronate-rich heparan sulfate species was also exerted at the same concentrations. The antiproliferative species was taken up to a greater degree than the inactive one, suggesting a requirement for internalization. However, competition experiments with dextran sulfate suggested that both the high-affinity and the low-affinity sites are involved in mediating the antiproliferative effect. Structural analysis of the inactive and active heparan sulphate preparations indicated that although sulphated L-iduronate appears essential for antiproliferative activity, it is not absolutely required for binding to the cells. Degradation of internalized heparan sulfate was analyzed by polyacrylamide gel electrophoresis using a sensitive detection technique. The inactive species was partially degraded, whereas the antiproliferative one was only marginally affected.

Details

Authors
Organisations
External organisations
  • Lund University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biochemistry and Molecular Biology
  • Other Basic Medicine

Keywords

  • Biological Transport, Cell Division, Cells, Cultured, Female, Fibroblasts, Heparitin Sulfate, Humans, Iduronic Acid, Pregnancy, Radioligand Assay, Journal Article, Research Support, Non-U.S. Gov't
Original languageEnglish
Pages (from-to)595-604
Number of pages10
JournalJournal of Cellular Biochemistry
Volume64
Issue number4
Publication statusPublished - 1997 Mar 15
Publication categoryResearch
Peer-reviewedYes