FIGURE 1.

Endogenous PP2A-family phosphatases regulate phospho-SK1 levels. A, whole cell extracts from cells overexpressing SK1 were incubated at 37 °C for the indicated times. Dephosphorylation of SK1 was assessed by immunoblotting with an antibody recognizing phospho-SK1 (upper panel), and total SK1 levels were confirmed by immunoblotting with anti-FLAG antibodies (lower panel). B, as in A, but reactions were incubated for 120 min the presence of fostriecin (1.6 μm) or I-2 (1 μm), to assess the relative contributions from PP2A- and PP1-family phosphatases, respectively. Results are representative of three independent experiments. The dividing lines indicate where lanes have been spliced to simplify viewing, but results in each panel are from a single experiment.