Figure 4

Transglutaminase activity persists after loss of TGM1 immunoreactivity in HEK293T cells. (a) HEK293T cells were transfected with TGM1, tagged with H6, or empty vector. The cells were collected by cytospin, fixed with methanol and subjected to TGM activity labeling (red) and immunofluorescence labeling with a primary antibody against TGM1 (green). Nuclear DNA was labeled with Hoechst 33258 dye (blue). White rectangles in images of the upper panels mark details that are enlarged in the middle panels. The arrows and numbers mark a cell exhibiting only TGM activity (arrow 1), a cell exhibiting only TGM1 immunofluorescence (arrow 2), and a cell displaying both TGM activity and TGM1 immunofluorescence (arrow 3). (b) Western blot analysis of cells transfected with empty vector or the expression vector for His-tagged (H6) TGM1. Primary antibodies against H6 and TGM1 were used to detect the recombinant protein with a predicted molecular mass of 100Â kDa. GAPDH was analyzed as a loading control. Uncropped images of the membranes are provided in Supplementary Fig. S2.