Impaired binding affinity of electronegative low-density lipoprotein (LDL) to the LDL receptor is related to nonesterified fatty acids and lysophosphatidylcholine content
Benitez, Sonia (Institut d'Investigació Biomèdica Sant Pau)
Villegas, Virtudes (Universitat Autònoma de Barcelona. Departament de Bioquímica i de Biologia Molecular)
Bancells, Cristina (Hospital de la Santa Creu i Sant Pau (Barcelona, Catalunya))
Jorba, Oscar (Hospital de la Santa Creu i Sant Pau (Barcelona, Catalunya))
González-Sastre, Francesc (Universitat Autònoma de Barcelona. Departament de Bioquímica i de Biologia Molecular)
Ordóñez, J. (Jordi) 1952- (Universitat Autònoma de Barcelona. Departament de Bioquímica i de Biologia Molecular)
Sanchez-Quesada, Jose Luis (Hospital de la Santa Creu i Sant Pau (Barcelona, Catalunya))

Date:	2004
Abstract:	The binding characteristics of electropositive [LDL(+)] and electronegative LDL [LDL(-)] subfractions to the LDL receptor (LDLr) were studied. Saturation kinetic studies in cultured human fibroblasts demonstrated that LDL(-) from normolipemic (NL) and familial hypercholesterolemic (FH) subjects had lower binding affinity than their respective LDL(+) fractions (P < 0. 05), as indicated by higher dissociation constant (K) values. FH-LDL(+) also showed lower binding affinity (P < 0. 05) than NL-LDL(+) (K, sorted from lower to higher affinity: NL-LDL(-), 33. 0 ± 24. 4 nM; FH-LDL(-), 24. 4 ± 7. 1 nM; FH-LDL(+), 16. 6 ± 7. 0 nM; NL-LDL(+), 10. 9 ± 5. 7 nM). These results were confirmed by binding displacement studies. The impaired affinity binding of LDL(-) could be attributed to altered secondary and tertiary structure of apolipoprotein B, but circular dichroism (CD) and tryptophan fluorescence (TrpF) studies revealed no structural differences between LDL(+) and LDL(-). To ascertain the role of increased nonesterified fatty acids (NEFA) and lysophosphatidylcholine (LPC) content in LDL-(-), LDL(+) was enriched in NEFA or hydrolyzed with secretory phospholipase A. Modification of LDL gradually decreased the affinity to LDLr in parallel to the increasing content of NEFA and/or LPC. Modified LDLs with a NEFA content similar to that of LDL(-) displayed similar affinity. ApoB structure studies of modified LDLs by CD and TrpF showed no difference compared to LDL(+) or LDL(-). Our results indicate that NEFA loading or phospholipase A lipolysis of LDL leads to changes that affect the affinity of LDL to LDLr with no major effect on apoB structure. Impaired affinity to the LDLr shown by LDL(-) is related to NEFA and/or LPC content rather than to structural differences in apolipoprotein B.
Grants:	Ministerio de Ciencia y Tecnología SAF2001-04080-C02-01 Instituto de Salud Carlos III PI030885
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Language:	Anglès
Document:	Article ; recerca ; Versió sotmesa a revisió
Subject:	Binding affinity ; Familial hypercholesterolemic (FH) ; Nonesterified fatty acids (NEFA)
Published in:	Biochemistry, Vol. 43 Núm. 50 (21 2004) , p. 15863-15872, ISSN 0006-2960

DOI: 10.1021/bi048825z

27 p, 1.9 MB

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