Fig. 1. Effects of protein phosphatase inhibitors on MARCKS translocation and myoblast fusion. Myoblasts were treated with 25 nM okadaic acid (lane O) or 0.5 µM tautomycin (lane T) at the time of medium change, as described in Materials and Methods. The cells that had been cultured for 24 hours in the presence of okadaic acid or tautomycin were freed of the drug by changing the medium (lanes F_O and F_T, respectively). These cells were further cultured for the next 48 and 24 hours, respectively. Lane C indicates the cells cultured for 72 hours without any treatment. Total cell lysates (A) and membrane fractions (B) were prepared and subjected to SDS-PAGE followed by immunoblot analysis using an anti-MARCKS antibody. The arrows indicate MARCKS. The cells cultured as above were subjected to Giemsa staining to determine the degree of cell fusion (C). Cells containing more than three nuclei were regarded as fused cells.