CELL CHOLESTEROL REMOVAL BY DISCOIDAL HDL: INFLUENCE OF APOLIPOPROTEIN A-I HELIX REGISTRY

CUELLAR, LUZ ANGELA; PRIETO , EDUARDO DANIEL; CABALEIRO, LAURA VIRGINIA; GONZALEZ, MARINA C; GARDA, HORACIO ALBERTO

Puerto Madryn

Congreso; XLVI Reunión Anual de SAIB Puerto Madryn, 30-3/noviembre de 2010; 2010

Sociedad Argentina de Investigaciones Bioquímicas

Discoidal high-density lipoproteins (dHDL) are key intermediates in apolipoprotein A-I (apoAI) mediated cell lipid efflux. Due to thedifficulty of dHDL isolation, the current knowledge about these complexes comes from studies using dHDL reconstituted by detergentdialysis, although they can also be generated by the spontaneous reaction of apoAI with phospholipid vesicles at their phase transitiontemperature, a procedure that may be similar to the "in vivo" apoAI lipidation.We show evidence that spontaneously generated dHDL are more active than those obtained by cholate-dialysis in promoting cholesterolefflux from murine macrophagues. Moreover, through FRET measurements with single tryptophan or fluorescent-labeled cysteine mutantsof apoAI, it is detected that spontaneously generated dHDL consist predominantly of a unique apoAI configuration with a fix helix registry(LL5/2) in opposition to cholate-dialysis generated dHDL which consist of at least two configurations of variable helix registry (LL5/5 andLL5/2).Thus, our data indicate that only dHDL containig the LL5/2 configuration promote cell cholesterol efflux. As we previously proposed, thecentral 3-4 helix pairs form an intermolecular membrane-inserting bundle, which is possible in LL5/2 but not in LL5/5 configuration.Therefore, the formation of this intermolecular bundle should be essential for the dHDL activity.