FIGURE 5.

Nb-(146–493) is a selective inhibitor of striatal PP1γ₁. A, PP1γ₁ or PP1β were immunoprecipitated (IP) from whole striatal extracts. Upper panels show representative immunoblots confirming the immunoprecipitation specificity. Lower panels show activities in the immunoprecipitates measured using [³²P]phosphorylase a in the presence of 2.5 nm okadaic acid (O.A.) alone or with the addition of 2.5 μm okadaic acid or 1 μm Nb-(146–493). Nb-(146–493) inhibited immunoprecipitated PP1γ₁, but not immunoprecipitated PP1β. B, phosphatase activity in a control whole striatal extract was assayed using [³²P]phosphorylase a in the presence of indicated concentrations of okadaic acid (open diamonds), inhibitor-2 (solid squares), Nb-(146–493) (solid circles), or Nb-(146–453) (open inverted triangles). Each point is the mean ± S.E. of 2–6 observations, plotted as a percentage of total activity (without inhibitor). PP1 accounts for 75–80% of the total activity when estimated using okadaic acid or inhibitor-2 (see “Results”), but Nb-(146–493) inhibits only ≈48% of the total activity.