Bcl-2 targets protein phosphatase 1 alpha to bad

The diverse forms of protein phosphatase 1 (PP1) in vivo result from the as sociation of the catalytic subunit with different regulatory subunits. We r ecently have described that PP1 alpha is a Ras-activated Bad phosphatase th at regulates IL-2 deprivation-induced apoptosis. With the yeast two-hybrid system, GST fusion proteins, indirect immunofluorescence, and coimmunopreci pitation, we found that Bcl-2 interacts with PP1 alpha and Bad. In contrast , Bad did not interact with 14-3-3 protein. Bcl-2 depletion decreased phosp hatase activity and association of PP1 alpha to Bad. Bcl-2 contains the RIV AF motif, analogous to the well characterized R/KXV/IXF consensus motif sha red by most PP1-interacting proteins. This sequence is involved in the bind ing of Bcl-2 to PP1 alpha. Disruption of Bcl-2/PP1 alpha association strong ly decreased Bcl-2 and Bad-associated phosphatase activity and formation of the trimolecular complex. These results suggest that Bcl-2 targets PP1 alp ha to Bad.