Unraveling Intestinal Fatty Acid Binding Proteins Functions: Analysis of FABP-Membrane and FAB_Protein Interactions

FALOMIR LOCKHART LJ; GUERBI MX; FRANCHINI GR; STORCH J; CÓRSICO B

Buzios

Congreso; VII IACB/XXXVI Reunión Anual de la SAB; 2009

Federación de Sociedades de Biofísicas del Cono Sur

Introduction: Intestinal enterocytes express large and near equal quantities of two small homologous fatty acid binding proteins (FABPs): intestinal (IFABP) and liver FABP (LFABP). It has long been hypothesized that FABPs participate in the intracellular transit and processing of the large quantities of fatty acids (FA) absorbed by the intestine, but their specific function are still poorly understood. In particular, it is currently not known why a single cell type contains two distinct types of FABP. Objective: We expect to identify the interaction partners of intestinal FABPs in order to describe the molecular crosstalk relevant for its biological functions. Methods: In this work, we took advantage of different structural variants of intestinal FABPs and a battery of biochemical and biophysical methodologies to analyze its interaction with membranes and other proteins. Tb/DPA complex leakage, binding to sucrose loaded vesicles, Cyt c competition assay and crosslinking to radiolabeled photoactivable phospholipid were employed to study different factors (vesicle curvature, ligand nature, lipid composition, etc) that modulate the interaction of FABPs with model membranes. On the other hand, a fluorescence based assay was employed to analyze transfer of FA analogs between IFABP and LFABP in a stopped-flow module. Results: Lipid composition and ligand binding show strong changes in membrane interaction properties of IFABP and LFABP, as evidenced by different techniques. Collisional transfer of fluorescent FA suggests functional interaction between these intestinal FABPs. Conclusions: Intestinal FABPs could interact differentially with each other and with subcellular membranous fractions accordingly with ligand binding and phospholipid characteristics. These results in vitro may reflect in vivo functions of intestinal FABPs and increasing evidence supports the idea that FABPs participate and modulate several cell functions.