The EM structure of the TRAPPIII complex leads to the identification of a requirement for COPII vesicles on the macroautophagy pathway.
The transport protein particle (TRAPP) III complex, comprising the TRAPPI complex and additional subunit Trs85, is an autophagy-specific guanine nucleotide exchange factor for the Rab GTPase Ypt1 that is recruited to the phagophore assembly site when macroautophagy is induced. We present the single-particle electron microscopy structure of TRAPPIII, which reveals that the dome-shaped Trs85 subunit associates primarily with the Trs20 subunit of TRAPPI. We further demonstrate that TRAPPIII binds the coat protein complex (COP) II coat subunit Sec23. The COPII coat facilitates the budding and targeting of ER-derived vesicles with their acceptor compartment. We provide evidence that COPII-coated vesicles and the ER-Golgi fusion machinery are needed for macroautophagy. Our results imply that TRAPPIII binds to COPII vesicles at the phagophore assembly site and that COPII vesicles may provide one of the membrane sources used in autophagosome formation. These events are conserved in yeast to mammals.
Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115.
Dongyan
D
Tan
Yiying
Y
Cai
Juan
J
Wang
Jinzhong
J
Zhang
Shekar
S
Menon
Hui-Ting
HT
Chou
Susan
S
Ferro-Novick
Karin M
KM
Reinisch
Thomas
T
Walz
D000818:Animals; D001343:Autophagy / Q000502:physiology*; D022181:COP-Coated Vesicles / Q000378:metabolism / Q000502:physiology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D018274:Electroporation; D004926:Escherichia coli; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000378:metabolism
D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP