title: TRAPPII subunits are required for the specificity switch of a Ypt-Rab GEF.
abstract: Ypt-Rab GTPases are key regulators of the various steps of intracellular trafficking. Guanine nucleotide-exchange factors (GEFs) regulate the conversion of Ypt-Rabs to the GTP-bound state, in which they interact with effectors that mediate all the known aspects of vesicular transport. An interesting possibility is that Ypt-Rabs coordinate separate steps of the transport pathways. The conserved modular complex TRAPP is a GEF for the Golgi gatekeepers Ypt1 and Ypt31/32 (Refs 5-7). However, it is not known how Golgi entry and exit are coordinated. TRAPP comes in two configurations: the seven-subunit TRAPPI is required for endoplasmic reticulum-to-Golgi transport, whereas the ten-subunit TRAPPII functions in late Golgi. The two essential TRAPPII-specific subunits Trs120 and Trs130 have been identified as Ypt31/32 genetic interactors. Here, we show that they are required for switching the GEF specificity of TRAPP from Ypt1 to Ypt31. Moreover, a trs130ts mutation confers opposite effects on the intracellular localization of these GTPases. We suggest that the Trs120-Trs130 subcomplex joins TRAPP in the late Golgi to switch its GEF activity from Ypt1 to Ypt31/32. Such a 'switchable' GEF could ensure sequential activation of these Ypts, thereby coordinating Golgi entry and exit.
authors.affiliation: Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Molecular Biology Research Building, 900 South Ashland Avenue, Chicago, IL 60607, USA.
authors.forename: Nadya
authors.initials: N
authors.lastname: Morozova
authors.forename: Yongheng
authors.initials: Y
authors.lastname: Liang
authors.forename: Andrei A
authors.initials: AA
authors.lastname: Tokarev
authors.forename: Shu H
authors.initials: SH
authors.lastname: Chen
authors.forename: Randal
authors.initials: R
authors.lastname: Cox
authors.forename: Jelena
authors.initials: J
authors.lastname: Andrejic
authors.forename: Zhanna
authors.initials: Z
authors.lastname: Lipatova
authors.forename: Vicki A
authors.initials: VA
authors.lastname: Sciorra
authors.forename: Scott D
authors.initials: SD
authors.lastname: Emr
authors.forename: Nava
authors.initials: N
authors.lastname: Segev
mesh_terms: D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C107845:BET1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D021122:Protein Subunits; D050767:Qc-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP; D006153:Guanosine Diphosphate; C087905:YPT31 protein, S cerevisiae; C060755:YPT1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins