Activated Rac1 GTPase Translocates Protein Phosphatase 5 to the Cell Membrane and Stimulates Phosphatase Activity in Vitro

Department of Biochemistry and Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2009; 285(6):3872-82. DOI: 10.1074/jbc.M109.088427
Source: PubMed


Physiological studies of ion channel regulation have implicated the Ser/Thr protein phosphatase 5 (PP5) as an effector of
Rac1 GTPase signaling, but direct biochemical evidence for PP5 regulation by Rac1 is lacking. In this study we used immunoprecipitation,
in vitro binding, cellular fractionation, and immunofluorescence techniques to show that the tetratricopeptide repeat domain of PP5
interacts specifically and directly with active Rac1. Consequently, activation of Rac1 promoted PP5 translocation to the plasma
membrane in intact cells and stimulated PP5 phosphatase activity in vitro. In contrast, neither constitutively active RhoA-V14 nor dominant negative Rac1N17, which preferentially binds GDP and retains
an inactive conformation, bound PP5 or stimulated its activity. In addition, Rac1N17 and Rac1(PBRM), a mutant lacking the
C-terminal polybasic region required for Rac1 association with the membrane, both failed to cause membrane translocation of
PP5. Mutation of predicted contact residues in the PP5 tetratricopeptide repeat domain or within Rac1 also disrupted co-immunoprecipitation
of Rac1-PP5 complexes and membrane translocation of PP5. Specific binding of PP5 to activated Rac1 provides a direct mechanism
by which PP5 can be stimulated and recruited to participate in Rac1-mediated signaling pathways.

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    • "Recent studies have confirmed a role for the PP5 TPR domain in specific and direct interaction with Rac, allowing Rac control over PP5 phosphatase activity and localisation to the cellular membrane (Chatterjee et al. 2010). Another interesting feature of p67 phox and PP5 is the involvement of their TPR regions in intramolecular interactions . "
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