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.
"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 . "
[Show abstract][Hide abstract] ABSTRACT: The tetratricopeptide repeat (TPR) motif is one of many repeat motifs that form structural domains in proteins that can act as interaction scaffolds in the formation of multi-protein complexes involved in numerous cellular processes such as transcription, the cell cycle, protein translocation, protein degradation and host defence against invading pathogens. The crystal structures of many TPR domain-containing proteins have been determined, showing TPR motifs as two anti-parallel α-helices packed in tandem arrays to form a structure with an amphipathic groove which can bind a target peptide. This is however not the only mode of target recognition by TPR domains, with short amino acid insertions and alternative TPR motif conformations also shown to contribute to protein interactions, highlighting diversity in TPR domains and the versatility of this structure in mediating biological events.
[Show abstract][Hide abstract] ABSTRACT: Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication accompanied with repetitive behavioral patterns and unusual stereotyped interests. Autism is considered a highly heterogeneous disorder with diverse putative causes and associated factors giving rise to variable ranges of symptomatology. Incidence seems to be increasing with time, while the underlying pathophysiological mechanisms remain virtually uncharacterized (or unknown). By systematic review of the literature and a systems biology approach, our aims were to examine the multifactorial nature of autism with its broad range of severity, to ascertain the predominant biological processes, cellular components, and molecular functions integral to the disorder, and finally, to elucidate the most central contributions (genetic and/or environmental) in silico. With this goal, we developed an integrative network model for gene-environment interactions (GENVI model) where calcium (Ca2+) was shown to be its most relevant node. Moreover, considering the present data from our systems biology approach together with the results from the differential gene expression analysis of cerebellar samples from autistic patients, we believe that RAC1, in particular, and the RHO family of GTPases, in general, could play a critical role in the neuropathological events associated with autism.
Neuromolecular medicine 03/2013; 15(2):364-383. DOI:10.1007/s12017-013-8224-3 · 3.68 Impact Factor
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