Formation of amyloid-like substance from .BETA.2-microglobulin in vitro: Role of serum amyloid P component.

ABSTRACT Lipopolysaccharide (LPS) is an amphipathic macromolecule that is highly aggregated in aqueous preparations. LPS-binding protein (LBP) catalyzes the transfer of single LPS molecules, segregated from an LPS aggregate, to high-density lipoproteins (HDL), which results in the neutralization of LPS. When fluorescein isothiocyanate-labeled LPS (FITC-LPS) is used, this transfer of LPS monomers to HDL can be measured as an increase in fluorescence due to dequenching of FITC-LPS. Recently, serum amyloid P component (SAP) was shown to neutralize LPS in vitro, although only in the presence of low concentrations of LBP. In this study, we show that SAP prevented HDL-mediated dequenching of FITC-LPS, even in the presence of high concentrations of LBP. Human bactericidal/permeability-increasing protein (BPI), a very potent LPS-binding and -neutralizing protein, also prevented HDL-mediated dequenching of FITC-LPS. Furthermore, SAP inhibited HDL-mediated neutralization of both rough and smooth LPS in a chemiluminescence assay quantifying the LPS-induced priming of neutrophils in human blood. SAP bound both isolated HDL and HDL in serum. Using HDL-coated magnetic beads prebound with SAP, we demonstrated that HDL-bound SAP prevented the binding of LPS to HDL. We suggest that SAP, by preventing LPS binding to HDL, plays a regulatory role, balancing the amount of LPS that, via HDL, is directed to the adrenal glands.

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New insights into the role of serum amyloid P component, a novel lipopolysaccharide-binding protein

FEMS Immunology & Medical Microbiology ◽

10.1111/j.1574-695x.1999.tb01390.x ◽

1999 ◽

Vol 26 (3-4) ◽

pp. 197-202 ◽

Cited By ~ 5

Author(s):

Carla J.C Haas

Keyword(s):

Binding Protein ◽

Serum Amyloid ◽

Lipopolysaccharide Binding Protein ◽

Amyloid P Component ◽

Serum Amyloid P ◽

Serum Amyloid P Component ◽

Amyloid P ◽

Lipopolysaccharide Binding

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Role of Shiga toxin 2 (Stx2)-binding protein, human serum amyloid P component (HuSAP), in Shiga toxin-producing Escherichia coli infections: assumption from in vitro and in vivo study using HuSAP and anti-Stx2 humanized monoclonal antibody TMA-15

Biochemical and Biophysical Research Communications ◽

10.1016/s0006-291x(03)00901-x ◽

2003 ◽

Vol 305 (4) ◽

pp. 1057-1060 ◽

Cited By ~ 13

Author(s):

Tsuyoshi Kimura ◽

Shinobu Tani ◽

Masamichi Motoki ◽

Yoh-ichi Matsumoto

Keyword(s):

Shiga Toxin ◽

Amyloid P Component ◽

Serum Amyloid P ◽

Serum Amyloid P Component ◽

Humanized Monoclonal Antibody ◽

Shiga Toxin 2 ◽

Amyloid P

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Human serum amyloid P component, a circulating lectin with specificity for the cyclic 4,6-pyruvate acetal of galactose. Interactions with various bacteria

Biochemical Journal ◽

10.1042/bj2250107 ◽

1985 ◽

Vol 225 (1) ◽

pp. 107-111 ◽

Cited By ~ 64

Author(s):

C R K Hind ◽

P M Collins ◽

M L Baltz ◽

M B Pepys

Keyword(s):

Xanthomonas Campestris ◽

Group A Streptococcus ◽

Serum Amyloid ◽

Amyloid P Component ◽

Serum Amyloid P ◽

Serum Amyloid P Component ◽

Group A ◽

Amyloid P ◽

Specific Ligand

Serum amyloid P component (SAP), a normal plasma glycoprotein, has recently been shown to have Ca2+-dependent binding specificity for methyl 4,6-O-(1-carboxyethylidene)-beta-D-galactopyranoside (MO beta DG) [Hind, Collins, Renn, Cook, Caspi, Baltz & Pepys (1984) J. Exp. Med. 159, 1058-1069]. SAP was found to bind in vitro to Klebsiella rhinoscleromatis, the cell wall of which is known to contain this particular cyclic pyruvate acetal of galactose. SAP also bound in similar amounts (approx. 6000 molecules per organism) to group A Streptococcus pyogenes, but very much less was taken up on Xanthomonas campestris, which contains the 4,6-cyclic pyruvate acetal of mannose. No SAP bound to Escherichia coli, which contains the 4,6-cyclic pyruvate acetal of glucose, or to Streptococcus pneumoniae type 4, which contains the 2,3-cyclic pyruvate acetal of alpha- rather than beta-galactopyranoside, or to other organisms (Streptococcus agalactiae, Staphylococcus aureus and Staphylococcus epidermidis), the carbohydrate structures of which are less well characterized. Binding of SAP to those organisms which it did recognize was completely inhibited or reversed by millimolar concentrations of free MO beta DG. SAP, a human plasma protein, thus behaves as a lectin and may be a useful probe for its particular specific ligand in the cell walls of bacteria and other organisms.

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