Significance of GTP hydrolysis in Ypt1p-regulated endoplasmic reticulum to Golgi transport revealed by the analysis of two novel Ypt1-GAPs

Anna De Antoni, Jana Schmitzová, Hans Heinrich Trepte, Dieter Gallwitz, Štefan Albert

Research output: Contribution to journalArticle

Abstract

We here report on the identification and detailed biochemical characterization of two novel GTPase-activating proteins, Gyp5p and Gyp8p, whose efficient substrate is Ypt1p, a Ypt/Rab-GTPase essential for endoplasmic reticulum-to-Golgi trafficking in yeast. Gyp5p accelerated the intrinsic GTPase activity of Ypt1p 4.2 × 104-fold and, surprisingly, the 40-fold reduced GTP hydrolysis rate of Ypt1 (Q67L) p 1.5 × 104-fold. At steady state, the two newly discovered GTPase-activating proteins (GAPs) as well as the previously described Gyp1p, which also uses Ypt1p as the preferred substrate, display different subcellular localization. To add to an understanding of the significance of Ypt1p-bound GTP hydrolysis in vivo, yeast strains expressing the GTPase-deficient Ypt1(Q67L)p and having different Ypt1-GAP genes deleted were created. Depending on the genetic background, different mutants exhibited growth defects at low temperature and, already at permissive temperature, various morphological alterations resembling autophagy. Transport of proteins was not significantly impaired. Growth defects of Ypt1(Q67L)-expressing cells could be suppressed on high expression of all three Ypt1-GAPs. We propose that permanently active Ypt1p leads to increased vesicle fusion, which might induce previously unnoticed autophagic degradation of exaggerated membrane-enclosed structures. The data indicate that hydrolysis of Ypt1p-bound GTP is a prerequisite for a balanced vesicle flow between endoplasmic reticulum and Golgi compartments.

Original languageEnglish
Pages (from-to)41023-41031
Number of pages9
JournalJournal of Biological Chemistry
Volume277
Issue number43
DOIs
Publication statusPublished - Oct 25 2002

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'Significance of GTP hydrolysis in Ypt1p-regulated endoplasmic reticulum to Golgi transport revealed by the analysis of two novel Ypt1-GAPs'. Together they form a unique fingerprint.

  • Cite this