Localization of endogenously and ectopically expressed HA-TGN38 in control, Syt IX knocked-down, or Syt IX-overexpressing RBL cells. (A) Control RBL (ii,v,viii) RBL-Syt IX⁻ (i,iv,vii) and RBL-Syt IX⁺ (iii,vi,ix) cells were either labeled with monoclonal anti-TGN38 (i-iii) or were transiently transfected with HA-TGN38 cDNA (iv-ix), grown on glass coverslips for 48 hours, and subsequently labeled with monoclonal anti-HA antibodies followed by Cy3-conjugated donkey anti–mouse IgG. Bars equal 10 μm (i-vi) and 3 μm (vii-ix). (B) Control RBL, RBL-Syt IX⁻, and RBL-Syt IX⁺ cells were transiently transfected with HA-TGN38 cDNA and grown on glass coverslips for 48 hours. Cells were subsequently labeled with polyclonal anti-HA antibodies and monoclonal anti-TGN38 antibodies, followed by FITC- or Cy3-conjugated donkey anti–mouse or anti–rabbit IgG. Bars represent 3 μm.