Fig. 4. SNAP-23 was redistributed to the ER in cells expressing syntaxin 1. HeLa cells transfected with syntaxin 1 or co-transfected with syntaxin 1 and nSec1 as indicated were fixed and double stained for syntaxin 1 and endogenous SNAP-23 (A) or the plasma membrane marker Na⁺/K⁺ ATPase (B). Note the colocalization of SNAP-23 and ectopic syntaxin 1 (arrowhead) and the absence of SNAP-23 from the plasma membrane in cells expressing syntaxin 1 alone and the plasma membrane staining of SNAP-23 in non-transfected cells or in cells co-transfected with syntaxin 1 plus nSec1 (arrows). By contrast, endogenous Na⁺/K⁺ ATPase is not relocalized from the plasma membrane in syntaxin-1-expressing cells. Bar, 7 µm.