Syntaxin 11 is localized at the plasma membrane in
polarized but not in nonpolarized MDCK cells. A mixed population of
MDCK cells stably expressing human syntaxin 11 was grown either for
3 d on polycarbonate filters (A–D) or for 2 h on glass
coverslips (E). The cells were stained with antibodies against syntaxin
11 (A, C, and E, green), the lateral plasma membrane protein E-cadherin
(B and D), or the late endosomal/lysosomal protein LAMP-2 (E, red). B
and D also show nuclear DNA staining with propidium iodide. A and B
show horizontal confocal optical sections just above the nuclei. C and
D show vertical optical sections with the apical plasma membrane at the
top. Syntaxin 11 colocalizes with E-cadherin at the lateral plasma
membrane. E shows a representative horizontal optical section through
the middle of the cells. Syntaxin 11 does not significantly colocalize
with LAMP-2. The absence of a syntaxin 11 signal in neighboring
nonexpressing cells (A and E) demonstrates the specificity of the
antibody. Bars, 5 μm.