title: Importazole, a small molecule inhibitor of the transport receptor importin-β.
abstract: During interphase, the transport receptor importin-β carries cargoes into the nucleus, where RanGTP releases them. A similar mechanism operates in mitosis to generate a gradient of active spindle assembly factors around mitotic chromosomes. Importin-β and RanGTP have been implicated in additional cellular processes, but the precise roles of the Ran/importin-β pathway throughout the cell cycle remain poorly understood. We implemented a FRET-based, high-throughput small molecule screen for compounds that interfere with the interaction between RanGTP and importin-β and identified importazole, a 2,4-diaminoquinazoline. Importazole specifically blocks importin-β-mediated nuclear import both in Xenopus egg extracts and cultured cells, without disrupting transportin-mediated nuclear import or CRM1-mediated nuclear export. When added during mitosis, importazole impairs the release of an importin-β cargo FRET probe and causes both predicted and novel defects in spindle assembly. Together, these results indicate that importazole specifically inhibits the function of importin-β, likely by altering its interaction with RanGTP. Importazole is a valuable tool to evaluate the function of the importin-β/RanGTP pathway at specific stages during the cell cycle.
authors.affiliation: The Department of Molecular and Cell Biology, University of California, Berkeley, MC 3200 LSA, Berkeley, California 94720-3200, United States.
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Soderholm
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Bird
authors.forename: Petr
authors.initials: P
authors.lastname: Kalab
authors.forename: Yasaswini
authors.initials: Y
authors.lastname: Sampathkumar
authors.forename: Keisuke
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Michael
authors.initials: M
authors.lastname: Uehara-Bingen
authors.forename: Karsten
authors.initials: K
authors.lastname: Weis
authors.forename: Rebecca
authors.initials: R
authors.lastname: Heald
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D002457:Cell Extracts; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D057166:High-Throughput Screening Assays; D006801:Humans; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D010063:Ovum / Q000187:drug effects / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000187:drug effects; D014981:Xenopus; D028961:beta Karyopherins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D002457:Cell Extracts; D020690:GTPase-Activating Proteins; D028884:Karyopherins; D050778:NFATC Transcription Factors; D011799:Quinazolines; D018160:Receptors, Cytoplasmic and Nuclear; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C568452:importazole