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Cellular uptake of C4b-binding protein is mediated by heparan sulfate proteoglycans and CD91/LDL receptor-related protein

Spijkers, Patricia P; Denis, Cecile V; Blom, Anna LU and Lenting, Peter J (2008) In European Journal of Immunology 38(3). p.809-817
Abstract
CO-binding protein (C4BP) is a protein acting as a complement inhibitor and a carrier protein for anticoagulant protein S. Previously, we reported that the in vivo clearance of C4BP involves CD91, and that a CD91-interactive site overlaps the heparin-binding site within COP alpha-chains [26]. Here, we investigated the C4BP-CD91 interaction in more detail. Binding of C4BP to CD91 was unaffected by protein S, which associates with COP P-chain. Second, mutagenesis of cationic residues within C4BP alpha-chains impaired CD91 binding, reducing the affinity of triple mutant C4BP alpha/R39Q-R64Q-R66Q by 20-fold (Kd= 10 nM versus 214 nM for wild-type and mutant C4BP, respectively). Accordingly, intracellular degradation of this mutant by... (More)
CO-binding protein (C4BP) is a protein acting as a complement inhibitor and a carrier protein for anticoagulant protein S. Previously, we reported that the in vivo clearance of C4BP involves CD91, and that a CD91-interactive site overlaps the heparin-binding site within COP alpha-chains [26]. Here, we investigated the C4BP-CD91 interaction in more detail. Binding of C4BP to CD91 was unaffected by protein S, which associates with COP P-chain. Second, mutagenesis of cationic residues within C4BP alpha-chains impaired CD91 binding, reducing the affinity of triple mutant C4BP alpha/R39Q-R64Q-R66Q by 20-fold (Kd= 10 nM versus 214 nM for wild-type and mutant C4BP, respectively). Accordingly, intracellular degradation of this mutant by CD91-expressing cells was reduced to levels of CD91-deficient cells. Moreover, C4BP alpha/R39Q-R64Q-R66Q displayed a 3-fold prolonged survival compared to normal C4BP in in vivo clearance experiments. Since these residues also contribute to heparin binding, we explored the role of heparin-sulfate proteoglycans (HSPG) in the endocytosis of C4BP. The absence of HSPG was associated with a near complete absence of cell binding and intracellular degradation of C4BP. Apparently, the cellular uptake of C4BP depends on both HSPG and CD91, involving interactions with positively charged residues within C4BP alpha-chain. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
C4b-binding protein, CD91, heparin sulfate proteoglycans
in
European Journal of Immunology
volume
38
issue
3
pages
809 - 817
publisher
John Wiley & Sons
external identifiers
  • wos:000253919600020
  • scopus:43649086892
ISSN
1521-4141
DOI
10.1002/eji.200737722
language
English
LU publication?
yes
id
ab78c9ed-62ab-4bcc-9436-120124d17350 (old id 1186239)
date added to LUP
2008-09-03 13:55:41
date last changed
2017-01-01 04:40:04
@article{ab78c9ed-62ab-4bcc-9436-120124d17350,
  abstract     = {CO-binding protein (C4BP) is a protein acting as a complement inhibitor and a carrier protein for anticoagulant protein S. Previously, we reported that the in vivo clearance of C4BP involves CD91, and that a CD91-interactive site overlaps the heparin-binding site within COP alpha-chains [26]. Here, we investigated the C4BP-CD91 interaction in more detail. Binding of C4BP to CD91 was unaffected by protein S, which associates with COP P-chain. Second, mutagenesis of cationic residues within C4BP alpha-chains impaired CD91 binding, reducing the affinity of triple mutant C4BP alpha/R39Q-R64Q-R66Q by 20-fold (Kd= 10 nM versus 214 nM for wild-type and mutant C4BP, respectively). Accordingly, intracellular degradation of this mutant by CD91-expressing cells was reduced to levels of CD91-deficient cells. Moreover, C4BP alpha/R39Q-R64Q-R66Q displayed a 3-fold prolonged survival compared to normal C4BP in in vivo clearance experiments. Since these residues also contribute to heparin binding, we explored the role of heparin-sulfate proteoglycans (HSPG) in the endocytosis of C4BP. The absence of HSPG was associated with a near complete absence of cell binding and intracellular degradation of C4BP. Apparently, the cellular uptake of C4BP depends on both HSPG and CD91, involving interactions with positively charged residues within C4BP alpha-chain.},
  author       = {Spijkers, Patricia P and Denis, Cecile V and Blom, Anna and Lenting, Peter J},
  issn         = {1521-4141},
  keyword      = {C4b-binding protein,CD91,heparin sulfate proteoglycans},
  language     = {eng},
  number       = {3},
  pages        = {809--817},
  publisher    = {John Wiley & Sons},
  series       = {European Journal of Immunology},
  title        = {Cellular uptake of C4b-binding protein is mediated by heparan sulfate proteoglycans and CD91/LDL receptor-related protein},
  url          = {http://dx.doi.org/10.1002/eji.200737722},
  volume       = {38},
  year         = {2008},
}