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Ypt/Rab GTPases and Traffic Coordination
Author(s) -
Segev Nava,
Chen Shu,
Sundaram Geetanjali,
Suresh Veena,
Taussig David,
Tokarev Andrei,
Lipatova Zhanna
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.867.6
Subject(s) - rab , gtpase , golgi apparatus , guanine nucleotide exchange factor , microbiology and biotechnology , effector , biology , protein subunit , chemistry , biochemistry , endoplasmic reticulum , gene
Ypt/Rab GTPases are key regulators of intracellular trafficking in all eukaryotes. These GTPases are activated by guanine‐nucleotide exchange factors (GEFs). When in the GTP‐bound state, Ypt/Rabs interact with effectors that mediate individual steps of the trafficking pathways. An attractive possibility is that Ypt/Rabs and their activators not only regulate separate steps of transport pathways, but also coordinate them. We uncovered a number of novel mechanisms for such coordination in the yeast exocytic pathway. One such mechanism involves a dual‐specificity GEF. The conserved modular‐complex TRAPP is a GEF for the Golgi gatekeepers, Ypt1 and Ypt31/32. However, it is not known how Golgi entry and exit are coordinated. TRAPP exists in two configurations: the seven‐subunit TRAPPI is required for ER‐to‐Golgi transport, whereas the ten‐subunit TRAPPII functions in the late Golgi. We showed that in vitro, the two essential TRAPPII‐specific subunits, Trs120 and Trs130, are required for switching the GEF specificity of TRAPP from Ypt1 to Ypt31. In vivo, mutations in the TRAPPII‐specific subunits confer opposite effects on the intracellular localization of these GTPases. We suggest that the Trs120/Trs130 sub‐complex joins TRAPP in the late Golgi to switch its GEF specificity from Ypt1 to Ypt31/32. Such a switch‐able GEF could ensure sequential activation of these Ypts, thereby coordinating Golgi entry and exit.