IntroductionThe actin cytoskeleton participates in several cellular processes, including intracellular signaling, membrane trafficking, secretion, exoand endocytosis (1)(2)(3)(4)(5). Interactions between the actin cytoskeleton and the plasma membrane are thought to be important in many cellular events, including transport protein activity (6-9). The actin cytoskeleton may affect transport activity directly, by connecting transport proteins subunits to cytoskeletal elements Abstract Background: The brief incubation of opossum kidney (OK) cells with low P i results in Na ϩ /P i cotransport up-regulation and in substantial, but transient, cytoskeletal reorganization. In this study, we examined signaling events involved in the depolymerization of microfilaments. Results: Confocal laser scanning microscopy, immunoblot and immunoprecipitation experiments revealed villin co-localization with mainly actin short filaments and monomers, indicating that under the conditions used, villin acted as an actin-severing protein. Further analysis revealed that low concentrations of extracellular phosphate resulted in phospholipase CͲ1 (PLC-Ͳ1) translocation to the actin cytoskeleton, without increases in its tyrosine phosphorylation. Additionally, tyrosine phosphorylation