Transmission Electron Micrograph of transfected HL-1 cells labeled for TMEM43 with immunogold.

A and B. Single immunogold labeling experiments used 15 nm gold particles to label GFP. A. Immunogold-labeled TMEM43-WT cells. The label (large dot) is associated with the endoplasmic reticulum (arrows), nuclear envelope, and the nucleus (N). B. Immunogold-labeled TMEM43-S358L cells. Immunogold particles (large dot) are confined to bundles of cytoplasmic microfilaments (arrows) and what vacuolated endosomal structures (asterisk). The endoplasmic reticulum or nuclear envelope did not show TMEM43 expression. C and D. Double immunogold labeling experiments used 15 nm gold particles to label GFP and 5 nm gold particles to label TMEM43. C. Cytoplasm of a wild-type cell that has been labeled with both TMEM43 (small dot) and GFP (large dot) antibodies. Note the co-localization on the endoplasmic reticulum (arrows). D. Mutant protein labeled with antibody specific for TMEM43 (small dot) or the GFP Tag (large dot) were found in a large vacuolated structure (asterisk) as well as discrete clusters in the cytoplasm (arrows) of stably transfected cells. All bars equal 0.5 µm. E. Quantitative analysis of the distance between large gold particles (GFP-15 nm) and small gold particles (TMEM43-5 nm) in TMEM43-WT (open column) and TMEM43-S358L (filled column) cells. Data are expressed mean ± SD from three independent experiments.