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. 2017 Jul 4;8(33):54873–54888. doi: 10.18632/oncotarget.18966

Figure 4. Only full-length mature CD99 variants are present at the cell surface.

Figure 4

(A) HeLa cells transfected with CD99 WT, D92H or D92Y and meprin β showed co-staining of protease and substrate at the cell surface using confocal fluorescence microscopy. Of note, more intracellular staining was observed for the cancer-associated variants compared to CD99 WT. Bar = 20 μm. (B) Cell surface proteins of HeLa cells transfected with CD99 WT, D92H or D92Y and meprin β were labelled by primary amine biotinylation, pulled down using streptavidin sepharose beads, and analyzed by Western blot. When coexpressed with meprin β, CTF II fragments appeared for all CD99 variants. For accumulation of γ-secretase dependent cleavage products the specific inhibitor DAPT (0.6 μM, 18 h prior to cell lysis) was applied. Transferrin receptor served as control for correct biotinylation.