Figure 6. Phosphatase activities in CHO cells expressing phosphoinositide phosphatases.

CHO cells were transfected with the fusion proteins as described in Figure 1. Cellular extracts were then assayed for phosphatase activity using PtdIns(4,5)P₂ as a substrate and reaction products separated by TLC (A). Overexpression of SJ-1 and its 5-Pase domain, but not GFP or Sac1, lead to increased degradation of PtdIns(4,5)P₂ to phosphatidylinositol phosphate (PIP), indicating an increased PtdIns(4,5)P₂ phosphatase activity in these cells (B). Levels of PtdIns (PI), the final dephosphorylation product of PtdIns(4,5)P₂, are not changed significantly among the samples. Results are represented as means±S.D. (n=3).