Identification and characterization of the acidic pH binding sites for growth regulatory ligands of low density lipoprotein receptor-related protein-1

Thai Yen Ling, Chun Lin Chen, Yen Hua Huang, I. Hua Liu, Shuan Shian Huang, Jung San Huang

Research output: Contribution to journalArticle

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Abstract

The type V TGF-β receptor (TβR-V) plays an important role in growth inhibition by IGFBP-3 and TGF-β in responsive cells. Unexpectedly, TβR-V was recently found to be identical to the LRP-1/α2M receptor; this has disclosed previously unreported growth regulatory functions of LRP-1. Here we demonstrate that, in addition to expressing LRP-1, all cells examined exhibit low affinity but high density acidic pH binding sites for LRP-1 growth regulatory ligands (TGF-β1, IGFBP-3, and α2M*). These sites, like LRP-1, are sensitive to receptor-associated protein and calcium depletion but, unlike LRP-1, are also sensitive to chondroitin sulfate and heparin and capable of directly binding ligands, which do not bind to LRP-1. Annexin VI has been identified as a major membrane-associated protein capable of directly binding α2 M* at acidic pH. This is evidenced by: 1) structural and Western blot analyses of the protein purified from bovine liver plasma membranes by α2M* affinity column chromatography at acidic pH, and 2) dot blot analysis of the interaction of annexin VI and 125I- α2M*. Cell surface annexin VI is involved in 125I-TGF-β1 and 125I-α 2M* binding to the acidic pH binding sites and 125I-α2M* binding to LRP-1 at neutral pH as demonstrated by the sensitivity of cells to pretreatment with anti-annexin VI IgG. Cell surface annexin VI is also capable of mediating internalization and degradation of cell surface-bound 125-TGF-β1 and 125I-α2M* at pH 6 and of forming ternary complexes with 125I-α2M* and LRP-1 at neutral pH as demonstrated by co-immunoprecipitation. Trifluoperazine and fluphenazine, which inhibit ligand binding to the acidic pH binding sites, block degradation after internalization of cell surface-bound 125I-TGF- β1 or 125I-α2M*. These results suggest that cell surface annexin VI may function as an acidic pH binding site or receptor and may also function as a co-receptor with LRP-1 at neutral pH.

Original languageEnglish
Pages (from-to)38736-38748
Number of pages13
JournalJournal of Biological Chemistry
Volume279
Issue number37
DOIs
Publication statusPublished - Sep 10 2004

Fingerprint

Annexin A6
Low Density Lipoprotein Receptor-Related Protein-1
Binding Sites
Ligands
Growth
Insulin-Like Growth Factor Binding Protein 3
Fluphenazine
Affinity chromatography
Trifluoperazine
Degradation
Column chromatography
Chondroitin Sulfates
Cell membranes
Liver
Heparin
Membrane Proteins
Proteins
Immunoglobulin G
Calcium
Affinity Chromatography

ASJC Scopus subject areas

  • Biochemistry

Cite this

Identification and characterization of the acidic pH binding sites for growth regulatory ligands of low density lipoprotein receptor-related protein-1. / Ling, Thai Yen; Chen, Chun Lin; Huang, Yen Hua; Liu, I. Hua; Huang, Shuan Shian; Huang, Jung San.

In: Journal of Biological Chemistry, Vol. 279, No. 37, 10.09.2004, p. 38736-38748.

Research output: Contribution to journalArticle

Ling, Thai Yen ; Chen, Chun Lin ; Huang, Yen Hua ; Liu, I. Hua ; Huang, Shuan Shian ; Huang, Jung San. / Identification and characterization of the acidic pH binding sites for growth regulatory ligands of low density lipoprotein receptor-related protein-1. In: Journal of Biological Chemistry. 2004 ; Vol. 279, No. 37. pp. 38736-38748.
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AU - Huang, Shuan Shian

AU - Huang, Jung San

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