Modular TRAPP Complexes Regulate Intracellular Protein Trafficking Through Multiple Ypt/Rab GTPases in Saccharomyces cerevisiae
Shenshen Zou, Yutao Liu, Xiu Qi Zhang, Yong Chen, Min Ye, Xiaoping Zhu, Shu Yang, Zhanna Lipatova, Yongheng Liang, Nava Segev

Abstract

Ypt/Rab are key regulators of intracellular trafficking in all eukaryotic cells. In yeast, Ypt1 is essential for endoplasmic reticulum (ER)-to-Golgi transport, whereas Ypt31/32 regulate Golgi-to-plasma membrane and endosome-to-Golgi transport. TRAPP is a multisubunit complex that acts as an activator of Ypt/Rab GTPases. Trs85 and Trs130 are two subunits specific for TRAPP III and TRAPP II, respectively. Whereas TRAPP III was shown to acts as a Ypt1 activator, it is still controversial whether TRAPP II acts as a Ypt1 or Ypt31/32 activator. Here, we use GFP-Snc1 as a tool to study transport in Ypt and TRAPP mutant cells. First, we show that expression of GFP-Snc1 in trs85Δ mutant cells results in temperature sensitivity. Second, we suggest that in ypt1ts and trs85Δ, but not in ypt31Δ/32ts and trs130ts mutant cells, GFP-Snc1 accumulates in the ER. Third, we show that overexpression of Ypt1, but not Ypt31/32, can suppress both the growth and GFP-Snc1 accumulation phenotypes of trs85Δ mutant cells. In contrast, overexpression of Ypt31, but not Ypt1, suppresses the growth and GFP-Snc1 transport phenotypes of trs130ts mutant cells. These results provide genetic support for functional grouping of Ypt1 with Trs85-containing TRAPP III and Ypt31/32 with Trs130-containing TRAPP II.

  • Received November 3, 2011.
  • Accepted February 26, 2012.
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