Modulation of ATPase activity of liposome reconstituted ABCG1 by polyphenols

DE ATHAYDE MONCORVO, A; MORERO R; MINAHK C

San Javier, Tucumán

Congreso; XLI Reunión Anual de la Sociedad Argentina de Biofísica; 2012

Sociedad Argentina de Biofísica

ABCG1 is a transporter with an unquestionable importance in cholesterol homeostasis. Its activity was shown to be regulated at transcriptional level by LXR and PPARs agonists including polyphenols. But it is unknown whether there are other mechanisms of up-regulation of ABCG1 activity. Human ABCG1 gene was cloned into the pCHm3H10C yeast shuttle vector. Saccharomyces cerevisiae BJ2168 was transformed using a variation of the lithium acetate protocol. The transporter was purified and reconstituted into proteoliposomes. ATPase activity was estimated by measuring inorganic phosphate in the presence of polyphenols. In addition, membrane fluidity as well as changes in membrane interphase properties and tryptophan environment were analyzed by fluorometric measurements. Polyphenols induced a nearly 2-fold increase in ATPase activity of reconstituted ABCG1. However, even though these compounds were able to increase membrane viscosity and polarity of the interphase in a concentration dependent manner, no correlation with activity changes was found. On the other hand, close interaction between ABCG1 and polyphenols is suggested from tryptophan emission spectra. This result supports the hypothesis that polyphenols may also activate ABCG1 by an alternative(s) mechanism(s). This work provides the foundation for the future implementation of this strategy in the evaluation of compounds on ABCG1 activity, enabling a quick and reliable identification of potentially active substances by in vitro activity assays. Therefore, it would speed up the finding of chemicals with beneficial cardiovascular properties.