Trs130 Participates in Autophagy Through GTPases Ypt31/32 in Saccharomyces cerevisiae

Abstract

Trs130 is a specific component of the TRAPP II (Transport protein particle II) complex, which functions as a guanine exchange factor (GEF) for Rab GTPases Ypt31/32. Ypt31/32 is known to be involved in autophagy, although the precise mechanism has not been thoroughly studied. In this study, we investigated the potential involvement of Trs130 in autophagy and found that both the cytoplasm-to-vacuole targeting (Cvt) pathway and starvation-induced autophagy were defective in a trs130ts (trs130 temperature-sensitive) mutant. Mutant cells could not transport Atg8 and Atg9 to the preautophagosomal structure/ phagophore assembly site (PAS) properly, resulting in multiple Atg8 dots and Atg9 dots dispersed in the cytoplasm. Some dots were trapped in the trans-Golgi. Genetic studies showed that the effect of the Trs130 mutation was downstream of Atg5 and upstream of Atg1, Atg13, Atg9 and Atg14 on the autophagic pathway. Furthermore, overexpression of Ypt31 or Ypt32, but not of Ypt1, rescued autophagy defects in trs130ts and trs65ts (Trs130-HA Trs120-myc trs65Δ) mutants. Our data provide mechanistic insight into how Trs130 participates in autophagy and suggest that vesicular trafficking regulated by GTPases/GEFs is important in the transport of autophagy proteins from the trans-Golgi to the PAS.

Trs20 is Required for TRAPP III Complex Assembly at the PAS and its Function in Autophagy

“…When compared with wild‐type cells, trs20ts and trs85Δ mutant cells exhibit similar defects in non‐selective autophagy and CVT (Figure A,B, respectively). However, because we have shown that Trs20 is required also for the assembly of TRAPP II , and mutations in the TRAPP II‐specific subunit Trs130 cause selective and non‐selective autophagy defects , the autophagy defects of trs20ts mutant cells do not show that it exerts its effect through TRAPP III. Therefore, we looked for an autophagy process that depends on TRAPP III but not on TRAPP II.…”

“…At the trans‐Golgi, the interaction of Trs20 with the TRAPP II ‐specific subunit Trs120 is required for the assembly of TRAPP II . This complex regulates Golgi‐to‐ PM and endosome‐to‐Golgi transport , and plays a role in CVT and non‐selective autophagy, but not in ER ‐phagy . Associations are shown by ‘+’, black arrows indicate complex conversion, unfilled arrows indicate function.…”

Ypt/Rab GTPases regulate two intersections of the secretory and the endosomal/lysosomal pathways

“…11,17 In contrast over-expression of Ypt31, but not Ypt1, suppresses the growth, Snc1 accumulation and autophagy phenotypes of trs130ts mutant cells. 17,[27][28][29][30] Our evidence, that accumulation of intracellular Snc1 in ypt1 and trs85D mutant cells reflects an ER-phagy block and not an endosome-to-Golgi transport block, undermines the main support for a role for Ypt1 and TRAPP III in this transport step. Moreover, we have 3 reservations for using the co-localization of fluorescently-tagged Ypt1 with Sec7 as support for its role in endosome-to-Golgi transport.…”

Elevated NIBP/TRAPPC9 mediates tumorigenesis of cancer cells through NFκB signaling

“…The trans -Golgi network is essential for cancer development and may represent a novel target for anti-cancer therapy [23]. TRAPPC10 and other TRAPP II-specific subunits are required for the transport of autophagy proteins from the trans -Golgi to a phagophore assembly site [24]. Autophagy is also shown to be a key mediator for tumorigenesis [25, 26].…”