Co-IP of endogenous PP1cδ and MYPT1 with NMHC IIA decreased after BIG1 or BIG2 depletion. Samples of total proteins before (5%, In) or from IP with control IgG or indicated antibodies were analyzed by Western blotting. (A) Proteins from IP of BIG1 (25%) or BIG2 (50%) were analyzed by Western blotting with antibodies against BIG1, BIG2, or PP1. (B) Proteins (50%) from NMHC IIA IP of extracts of cells incubated 72 h without (None) or with indicated siRNA were reacted with antibodies against PP1, BIG1, BIG2, NMHC IIA, and GAPDH. (C) Data from three experiments like that in B. *P < 0.01 vs. NT. (D) Proteins from IP of BIG1 (25%), BIG2 (50%), or PP1cδ (50%) were reacted with antibodies against PP1cδ, BIG1, or BIG2. (E) Cells were incubated for 72 h without or with siRNA before IP of NMHC IIA from extracts. (F) Data from three experiments like that in E.*P < 0.005 vs. NT. (G) Proteins from IP with control IgG (50%) or antibodies against BIG1 (25%), BIG2 (50%), or MYPT1 were reacted with antibodies against BIG1, BIG2, or MYPT1. (H) Effect of BIG1 or BIG2 depletion on co-IP of MYPT1 with NMHC IIA. (I) Data from three experiments like that in H. *P < 0.01 vs. NT.