β-Arrestins are important in chemoattractant receptor-induced granule release, a process that may involve Ral-dependent regulation of the actin cytoskeleton. We have identified the Ral GDP dissociation stimulator (Ral-GDS) as a β-arrestin-binding protein by yeast two-hybrid screening and co-immunoprecipitation from human polymorphonuclear neutrophilic leukocytes (PMNs). Under basal conditions, Ral-GDS is localized to the cytosol and remains inactive in a complex formed with β-arrestins. In response to formyl-Met-Leu-Phe (fMLP) receptor stimulation, β-arrestin–Ral-GDS protein complexes dissociate and Ral-GDS translocates with β-arrestin from the cytosol to the plasma membrane, resulting in the Ras-independent activation of the Ral effector pathway required for cytoskeletal rearrangement. The subsequent re-association of β-arrestin–Ral-GDS complexes is associated with the inactivation of Ral signalling. Thus, β-arrestins regulate multiple steps in the Ral-dependent processes that result in chemoattractant-induced cytoskeletal reorganization.
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