Fig. 6. The cytoplasmic domains of syntaxins 7 and 8 direct their internalization from the plasma membrane. PC12h cells were electroporated with c-myc-tagged wild-type syntaxins (a,d,g), transmembrane domain chimeras (b,e,h), or cytoplasmic domain chimeras (c,f,i), and were processed for antibody uptake experiments. After incubation for 24 hours, the cells were treated for an additional 48 hours with 20 mM sodium butyrate. The cells were incubated for 3 hours in the presence of mouse anti-c-myc antibody before fixing. The cells were fixed and stained with FITC-conjugated anti-mouse IgG. Incubation of wild-type syntaxin-expressing cells with anti-c-myc antibody resulted in efficient labeling of intracellular compartments. Similar results were obtained in cells expressing syn6-1, syn7-1 or syn8-1. However, incubation of cells expressing syn1-6, syn1-7 or syn1-8 with anti-c-myc antibody resulted in labeling only at the plasma membrane.