Fig. 4.

β1-Integrin from the apical and basolateral surface of polarized MDCK cells binds Gal-7. Polarized MDCK cells were treated with sulfo-NHS-biotin on the apical (6 filters) or basolateral (2 filters) surface, and biotinylated proteins were recovered with avidin-conjugated beads. Proteins recovered from the apical (Ap) or basolateral (BL) surface were pooled and then split in half for incubation with either GST-Gal-7 (7) or galectin-like HSPC15 (control; C) prebound to glutathione-beads. Samples were analyzed by immunoblotting (IB) with rabbit anti-β1-integrin antibodies. A: aliquots of total detergent extract (5% total) and recovered biotinylated proteins (10% Avidin) were included as controls. B: after overnight incubation, the beads were incubated with sucrose (nonspecific binding), and then lactose (specific binding), and released proteins were recovered for immunoblotting. Numbers on the left indicate the mobility of the Bio-Rad protein standards at 100 and 150 kDa.