Subcellular localization of SR-BI/CLA-1 after the supply of postprandial micelles.

<p>(A) Immunoelectron micrograph of SR-BI/CLA-1 in untreated differentiated Caco-2/TC7 cells. MV, microvilli; TW, terminal web (bar, 0.5 µm). Note the significant amount of intracellular trafficking SR-BI/CLA-1 in addition to its main apical localization (arrowheads). (B) Immunolocalization of SR-BI/CLA-1 (green channel) and sucrase isomaltase (SI, red channel) in differentiated Caco-2/TC7 cells before (T0) and after 5, 10 and 15 min of apical PPM supply. Panels represent XY acquisitions at the apical level (bar, 10 µm). Arrowheads show clusters of SR-BI/CLA-1. (C) Immunolocalization of SR-BI/CLA-1 in differentiated Caco-2/TC7 cells in the absence (control) or presence of PPM or IPM for 20 min (bar, 20 µm). Arrowheads show clusters of SR-BI/CLA-1 (D) Immunoelectron micrograph of SR-BI/CLA-1 in Caco-2/TC7 cells supplied with PPM (MV, microvilli). Arrowheads indicate SR-BI/CLA-1 clusters (bar, 100 nm). (E) Cell surface biotinylation assay for apical SR-BI/CLA-1. Caco-2/TC7 cells were cultured in the absence (0) or presence of PPM for the indicated times. Cells were then selectively labeled with non-permeant biotin at the apical (left panel) or basal surface (right panel). Biotinylated fractions were obtained as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004278#s2" target="_blank">Material and Methods</a>. Total cell lysates (total), apical and basal biotinylated fractions (left and right panel respectively) and non-apical fractions (non-apical) were analyzed in immunoblots of SR-BI/CLA-1, E-cadherin being used as a basolateral membrane marker.