Fig. 3. (A) TPA-induced downregulation of PKC is sensitive to a proteasome inhibitor. Control (empty-vector-transfected) RBL cells and RBL-Syt II^- cells were treated for 12 hours with TPA (50 nM) in the absence or presence of the lysosomal inhibitor (leupeptin, 10 µg/ml) or the proteasomal inhibitor (ALLN, 38.5 µg/ml). Cytosolic and membranal fractions were separated as described in the Materials and Methods, and the amount of PKC in each fraction was determined as described in Fig. 1. Data represent one of two separate experiments. (B) TPA-induced downregulation of PKC is sensitive to the PKC inhibitor Go 6976. Control (empty vector transfected) RBL cells and RBL-Syt II^- cells were treated for 12 hours with TPA (50 nM) in the absence or presence of the PKC inhibitor Go 6976 (100 nM). The cellular level of PKC was determined as described in Fig. 1. Data represent one of three separate experiments.

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