Figure 6. Ectopic expression of rER located missense mutants interferes with membrane processing of endogenous endoglin in HMEC-1 cells.

In order to analyse whether endoglin missense mutants might interfere with the processing of endogenous endoglin (Endoglin^endo) or not, HMEC-1 endothelial cells were transfected with EYFP-tagged mutants or the EYFP-tagged DRD1 receptor, as indicated (all false-coloured in red). The membrane localized DRD1 receptor, not known to interact with endoglin, served as a negative control. After 24 hours, non-permeabilized cells were immunostained with the endoglin-specific monoclonal antibody (mAb) SN6. Non-permeabilization allows endogenous endoglin only to be detected in the membrane (shown in green). Cells transfected with the endoglin missense mutants (indicated by arrows) show a clear reduction of green fluorescence for the endogenous endoglin in the membrane in comparison to adjacent non-transfected cells. Ectopic expression of the DRD1 receptor appeared to have little or no effect on the membrane presence of endogenous endoglin.