Molecular mechanism for changes in proteoglycan binding on compositional changes of the core and the surface of low-density lipoprotein-containing human apolipoprotein B100.
OBJECTIVE
The aim of this study was to investigate the molecular mechanism for changes in proteoglycan binding and LDL receptor affinity on two compositional changes in LDL that have been associated with atherosclerosis: cholesterol enrichment of the core and modification by secretory group IIA phospholipase A2 (sPLA2) of the surface.


RESULTS
Transgenic mice expressing recombinant apolipoprotein (apo) B and sPLA2 were generated. Recombinant LDL were isolated and tested for their proteoglycan and LDL receptor-binding activity. The results show site A (residues 3148-3158) in apoB100 becomes functional in sPLA2-modified LDL and that site A acts cooperatively with site B (residues 3359-3369), the primary proteoglycan-binding site in native LDL, in the binding of sPLA2-modified LDL to proteoglycans. Our results also show that cholesterol enrichment of LDL is associated with increased affinity for proteoglycans and for the LDL receptor. This mechanism is likely mediated by a conformational change of site B and is independent of site A in apoB100.


CONCLUSIONS
Site A in apoB100 becomes functional in sPLA2-modified LDL and acts cooperatively with site B resulting in increased proteoglycan-binding activity. The increased binding for proteoglycans of cholesterol-enriched LDL is solely dependent on site B.
Flood
Christofer
C
Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska Academy at Göteborg University, Göteborg, Sweden.
Gustafsson
Maria
M
Pitas
Robert E
RE
Arnaboldi
Lorenzo
L
Walzem
Rosemary L
RL
Borén
Jan
J
D019943:Amino Acid Substitution; D000818:Animals; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001161:Arteriosclerosis / Q000378:metabolism; D058578:Biglycan; D008078:Cholesterol, LDL / Q000378:metabolism; D058575:Decorin; D016326:Extracellular Matrix Proteins; D054501:Group II Phospholipases A2; D006801:Humans; D008045:Lions / Q000097:blood; D008077:Lipoproteins, LDL / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D013045:Species Specificity
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; C546884:BGN protein, human; C546885:Bgn protein, mouse; D058578:Biglycan; D008078:Cholesterol, LDL; C546878:DCN protein, human; C546879:Dcn protein, mouse; D058575:Decorin; D016326:Extracellular Matrix Proteins; D008077:Lipoproteins, LDL; D011509:Proteoglycans; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2