Contribution of the C-terminal end of apolipoprotein AI to neutralization of lipopolysaccharide endotoxic effect.
It is well known that high density lipoprotein (HDL) binds bacterial lipopolysaccharide (LPS) and neutralizes its toxicity. The aim of this work was to study changes in the apolipoprotein (apo) AI structure after its interaction with LPS as well as to determine the protein domain involved in that interaction. The presented data indicate that LPS does not lead to major changes in the structure of apoAI, judging from Trp fluorescence spectra. However, analysis of denaturation behavior and binding of ANS show that LPS induces a loosened protein conformation. Further evidence for an apoAI-LPS specific interaction was obtained by incubation of the protein with (125)I-ASD-LPS. The results show that multiple regions of the protein were able to interact with LPS, according to its amphiphatic nature. Finally, the contribution of the purified C-terminal fragment of the protein in the endotoxin neutralization was evaluated in comparison with the effect of apoAI. In both cases, the same decrease in tumor necrosis factor-α released was observed. This result suggests that the C-terminal half of apoAI is the main domain responsible of the neutralization effect of this protein. Our data may provide innovative pharmacological tools in endotoxin neutralization therapies.
Henning
María F
MF
Instituto de Investigaciones Bioquímicas La Plata, CCT La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.
Herlax
Vanesa
V
Bakás
Laura
L
D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism* / Q000494:pharmacology; D001386:Azides / Q000138:chemical synthesis / Q000378:metabolism*; D002460:Cell Line; D019446:Endotoxemia / Q000188:drug therapy; D004731:Endotoxins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000138:chemical synthesis / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
C047258:2-(4-azidosalicylamido)-1,3'-dithiopropionate-lipopolysaccharide; D016632:Apolipoprotein A-I; D001386:Azides; D004731:Endotoxins; D008070:Lipopolysaccharides; D010446:Peptide Fragments; D014409:Tumor Necrosis Factor-alpha