A new interaction between Abi-1 and βPIX involved in PDGF-activated actin cytoskeleton reorganisation

摘要

Members of the Rho family of GTPases are key regulators of the actin cytoskeleton.In particular,activated Rac 1stimulates membrane dorsal ruffle formation in response to platelet-derived growth factor (PDGF).Abl-interactor (Abi)-1 and βPIX,a guanine nucleotide exchange factor for Rac 1,localise at these Rac1-induced actin structures and playimportant roles in the induction of membrane dorsal ruffling in response to PDGF in fibroblasts.Here,we demonstratea novel interaction between Abi-1 and βPIX using the yeast two-hybrid system,in vitro pull-down assays,and in vivoco-immunoprecipitation experiments.In vitro,the C-terminal fragment of ]3PIX interacted with Abi-1,while in vivo theN-terminal fragment of βPIX interacted with Abi-1.The biological function of this interaction was investigated in mousefibroblasts in response to PDGF stimulation.Abi-1 and βPIX co-localised in the cytoplasm and to membrane dorsalruffles after PDGF treatment.We show that the co-expression of Abi-1 and truncated forms of βPIX in mouse fibroblastsblocked PDGF-induced membrane dorsal ruffles.Together,these results show that the interaction between Abi-1 andβPIX is involved in the formation of growth factor-induced membrane dorsal ruffles.