title: Secramine inhibits Cdc42-dependent functions in cells and Cdc42 activation in vitro.
abstract: Inspired by the usefulness of small molecules to study membrane traffic, we used high-throughput synthesis and phenotypic screening to discover secramine, a molecule that inhibits membrane traffic out of the Golgi apparatus by an unknown mechanism. We report here that secramine inhibits activation of the Rho GTPase Cdc42, a protein involved in membrane traffic, by a mechanism dependent upon the guanine dissociation inhibitor RhoGDI. RhoGDI binds Cdc42 and antagonizes its membrane association, nucleotide exchange and effector binding. In vitro, secramine inhibits Cdc42 binding to membranes, GTP and effectors in a RhoGDI-dependent manner. In cells, secramine mimics the effects of dominant-negative Cdc42 expression on protein export from the Golgi and on Golgi polarization in migrating cells. RhoGDI-dependent Cdc42 inhibition by secramine illustrates a new way to inhibit Rho GTPases with small molecules and provides a new means to study Cdc42, RhoGDI and the cellular processes they mediate.
authors.affiliation: Department of Cell Biology and the CBR Institute for Biomedical Research, Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Henry E
authors.initials: HE
authors.lastname: Pelish
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Peterson
authors.forename: Susana B
authors.initials: SB
authors.lastname: Salvarezza
authors.forename: Enrique
authors.initials: E
authors.lastname: Rodriguez-Boulan
authors.forename: Ji-Long
authors.initials: JL
authors.lastname: Chen
authors.forename: Mark
authors.initials: M
authors.lastname: Stamnes
authors.forename: Eric
authors.initials: E
authors.lastname: Macia
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Shair
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001552:Benzazepines / Q000138:chemical synthesis / Q000494:pharmacology*; D002417:Cattle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D020690:GTPase-Activating Proteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000187:drug effects* / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D010091:Oximes / Q000138:chemical synthesis / Q000494:pharmacology*; D013997:Time Factors; D020764:cdc42 GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D000199:Actins; D001552:Benzazepines; D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D010091:Oximes; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; C508970:secramine A; D020764:cdc42 GTP-Binding Protein