FIG. 6.

The acidic amino acid cluster EEDE and the FI motif but not serine phosphorylation are required for basolateral sorting. MDCK cells expressing Tac F766-793 FI→AA (a and b), Tac F766-793 EEDE→AAAA (c and d), TTF SS→AA (e and f) or TTF SS→DD (g and h) were grown as polarized cell monolayers and incubated at 37°C for 30 min with anti-Tac antibody added to the upper (panels a, c, e, and g) or lower (panels b, d, f, and h) compartment. Cells were then washed on ice, fixed, and permeabilized, and anti-Tac antibodies were visualized by using a labeled second antibody. Mutation of the FI and EEDE but not that of the serines subject to phosphorylation by CKII affects basolateral transport. Bar, 10 μm.