title: A Two-Tiered Mechanism Enables Localized Cdc42 Signaling during Enterocyte Polarization.
abstract: Signaling by the small GTPase Cdc42 governs a diverse set of cellular processes that contribute to tissue morphogenesis. Since these processes often require highly localized signaling, Cdc42 activity must be clustered in order to prevent ectopic signaling. During cell polarization, apical Cdc42 signaling directs the positioning of the nascent apical membrane. However, the molecular mechanisms that drive Cdc42 clustering during polarity establishment are largely unknown. Here, we demonstrate that during cell polarization localized Cdc42 signaling is enabled via activity-dependent control of Cdc42 mobility. By performing photoconversion experiments, we show that inactive Cdc42-GDP is 30-fold more mobile than active Cdc42-GTP. This switch in apical mobility originates from a dual mechanism involving RhoGDI-mediated membrane dissociation of Cdc42-GDP and Tuba-mediated immobilization of Cdc42-GTP. Interference with either mechanism affects Cdc42 clustering and as a consequence impairs Cdc42-mediated apical membrane clustering. We therefore identify a molecular network, comprised of Cdc42, the guanine nucleotide exchange factor (GEF) Tuba, and RhoGDI, that enables differential diffusion of inactive and active Cdc42 and is required to establish localized Cdc42 signaling during enterocyte polarization.
authors.affiliation: Molecular Cancer Research and Cancer Genomics Netherlands, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Lucas J M
authors.initials: LJM
authors.lastname: Bruurs
authors.affiliation: Molecular Cancer Research and Cancer Genomics Netherlands, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Susan
authors.initials: S
authors.lastname: Zwakenberg
authors.affiliation: Molecular Cancer Research and Cancer Genomics Netherlands, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Mirjam C
authors.initials: MC
authors.lastname: van der Net
authors.affiliation: Molecular Cancer Research and Cancer Genomics Netherlands, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Fried J
authors.initials: FJ
authors.lastname: Zwartkruis
authors.affiliation: Molecular Cancer Research and Cancer Genomics Netherlands, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, The Netherlands J.L.Bos@umcutrecht.nl.
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D020895:Enterocytes / Q000166:cytology* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008871:Microvilli / Q000378:metabolism; D011485:Protein Binding; D015398:Signal Transduction; D014404:Tubulin / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D014404:Tubulin; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020764:cdc42 GTP-Binding Protein
keywords: Cdc42; GTPase signaling; cell polarity; cell signaling; polarized epithelia