Physiologically active configuration of ApoA-I

CUELLAR ANGELA; PRIETO EDUARDO; CABALEIRO, L. V.; GARDA, H. A.; GONZALEZ MARINA CECILIA

Salta

Congreso; Annual meeting of the Argentinean Biophysical Society (SAB 2010). Latin American. Protein Society Meeting; 2010

SAB

Discoidal high-density lipoproteins (dHDL) are key intermediates in apolipoprotein A-I (apoAI) mediated cell lipid efflux. Due to the difficulty of dHDL isolation, the current knowledge about these complexes comes from studies using dHDL reconstituted by detergent dialysis, although they can also be generated by the spontaneous reaction of apoAI with phospholipid vesicles at their phase transition temperature, 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 cholesterol efflux from murine macrophagues. Moreover, through FRET measurements with single tryptophan or fluorescent-labeled cysteine mutants of 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 and LL5/2). Thus, our data indicate that only dHDL containig the LL5/2 configuration promote cell cholesterol efflux. As we previously proposed, the central 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.