Zou S, Liu Y, Zhang XQ, Chen Y, Ye M, Zhu X, Yang S, Lipatova Z, Liang Y, Segev N

Ypt/Rab are key regulators of intra-cellular 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 multi-subunit complex that acts as an activator of Ypt/Rab GTPases. Trs85 and Trs130 are two subunits specific ...

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for TRAPP III and TRAPP II, respectively. Whereas TRAPP III was shown to act 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 over-expression of Ypt1, but not Ypt31/32, can suppress both the growth and GFP-Snc1 accumulation phenotypes of trs85Δ mutant cells. In contrast, over-expression 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.

Date: Mar. 16, 2012

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