title: Investigation of the Interaction between Cdc42 and Its Effector TOCA1: HANDOVER OF Cdc42 TO THE ACTIN REGULATOR N-WASP IS FACILITATED BY DIFFERENTIAL BINDING AFFINITIES.
abstract: Transducer of Cdc42-dependent actin assembly protein 1 (TOCA1) is an effector of the Rho family small G protein Cdc42. It contains a membrane-deforming F-BAR domain as well as a Src homology 3 (SH3) domain and a G protein-binding homology region 1 (HR1) domain. TOCA1 binding to Cdc42 leads to actin rearrangements, which are thought to be involved in processes such as endocytosis, filopodia formation, and cell migration. We have solved the structure of the HR1 domain of TOCA1, providing the first structural data for this protein. We have found that the TOCA1 HR1, like the closely related CIP4 HR1, has interesting structural features that are not observed in other HR1 domains. We have also investigated the binding of the TOCA HR1 domain to Cdc42 and the potential ternary complex between Cdc42 and the G protein-binding regions of TOCA1 and a member of the Wiskott-Aldrich syndrome protein family, N-WASP. TOCA1 binds Cdc42 with micromolar affinity, in contrast to the nanomolar affinity of the N-WASP G protein-binding region for Cdc42. NMR experiments show that the Cdc42-binding domain from N-WASP is able to displace TOCA1 HR1 from Cdc42, whereas the N-WASP domain but not the TOCA1 HR1 domain inhibits actin polymerization. This suggests that TOCA1 binding to Cdc42 is an early step in the Cdc42-dependent pathways that govern actin dynamics, and the differential binding affinities of the effectors facilitate a handover from TOCA1 to N-WASP, which can then drive recruitment of the actin-modifying machinery.
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and.
authors.forename: Joanna R
authors.initials: JR
authors.lastname: Watson
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and the Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Fox
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nietlispach
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and the Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gallop
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and do202@cam.ac.uk.
authors.forename: Darerca
authors.initials: D
authors.lastname: Owen
authors.affiliation: From the Department of Biochemistry, 80 Tennis Court Road, University of Cambridge, Cambridge CB2 1GA and hrm28@cam.ac.uk.
authors.forename: Helen R
authors.identifier: 0000-0002-7890-7097
authors.initials: HR
authors.lastname: Mott
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins; D006801:Humans; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D020836:Protein Structure, Quaternary; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D002352:Carrier Proteins; C488976:FNBP1L protein, Xenopus; C482527:FNBP1L protein, human; D050556:Fatty Acid-Binding Proteins; C495771:WASL protein, human; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D029867:Xenopus Proteins; C559910:Cdc42 protein, Xenopus; D020559:Monomeric GTP-Binding Proteins
keywords: BAR domain; CDC42; CIP4; FBP17; TOCA1; WASP; actin; endocytosis; nuclear magnetic resonance (NMR); protein-protein interaction