Fig. 7.

MUC1 processing by γ-secretase occurs in multiple cell contexts. Isolated mouse uterine epithelial cells (Mouse UE) were cultured to confluence in serum-free medium and treated with or without cytokines, ±1 µM L685,458 for 96 h as described in “Experimental Procedures Section.” Note that CTF15 ran slightly larger (ca. 17 kDa) in mouse uterine epithelia (all mouse C-terminal forms were about 2 kDa larger than the human CT forms). Human breast cancer cell lines, ZR75–1 (Panel B) and T47D (Panel C) were grown as described in “Experimental Procedures Section,” ±10µM S2188 or 1 µM L685458 for 14 and 56 h, respectively, without cytokine stimulation. Cell lysates were probed with CT1 antibody. Note that CTF15 was constitutively expressed in ZR75 cells, but enhanced slightly in the presence of S2188.