Trs85 (Gsg1), a component of the TRAPP complexes, is required for the organization of the preautophagosomal structure during selective autophagy via the Cvt pathway.
Autophagosomes and Cvt vesicles are limited by two membrane layers. The biogenesis of these unconventional vesicles and the origin of their membranes are hardly understood. Here we identify in Saccharomyces cerevisiae Trs85, a nonessential component of the TRAPP complexes, to be required for the biogenesis of Cvt vesicles. The TRAPP complexes function in endoplasmic reticulum-to-Golgi and Golgi trafficking. Growing trs85delta cells show a defect in the organization of the preautophagosomal structure. Although proaminopeptidase I is normally recruited to the preautophagosomal structure, the recruitment of green fluorescent protein-Atg8 depends on Trs85. Autophagy proceeds in the absence of Trs85, albeit at a reduced rate. Our electron microscopic analysis demonstrated that the reduced autophagic rate of trs85delta cells does not result from a reduced size of the autophagosomes. Growing and starved cells lacking Trs85 did not show defects in vacuolar biogenesis; mature vacuolar proteinase B and carboxypeptidase Y were present. Also vacuolar acidification was normal in these cells. It is known that mutations impairing the integrity of the ER or Golgi block both autophagy and the Cvt pathway. But the phenotypes of trs85delta cells show striking differences to those seen in mutants with defects in the early secretory pathway. This suggests that Trs85 might play a direct role in the Cvt pathway and autophagy.
Meiling-Wesse
Khuyen
K
Center of Biochemistry and Molecular Cell Biology, Georg-August-University, Heinrich-Dueker-Weg 12, D-37073 Goettingen, Germany.
Epple
Ulrike D
UD
Krick
Roswitha
R
Barth
Henning
H
Appelles
Anika
A
Voss
Christiane
C
Eskelinen
Eeva-Liisa
EL
Thumm
Michael
M
D001343:Autophagy; D000071190:Autophagy-Related Protein 8 Family; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017353:Gene Deletion; D006056:Golgi Apparatus / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism* / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D013217:Starvation; D022161:Transport Vesicles / Q000378:metabolism / Q000648:ultrastructure; D014617:Vacuoles / Q000378:metabolism* / Q000648:ultrastructure; D033921:Vesicular Transport Proteins / Q000378:metabolism* / Q000648:ultrastructure
C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP; D049452:Green Fluorescent Proteins