title: Quantitative analysis of autophagy-related protein stoichiometry by fluorescence microscopy.
abstract: In yeast, approximately 31 autophagy-related (Atg) proteins have been identified. Most of them reside at the phagophore assembly site (PAS), although the function of the PAS mostly remains unclear. One reason for the latter is the lack of stoichiometric information regarding the Atg proteins at this site. We report the application of fluorescence microscopy to study the amount of Atg proteins at the PAS. We find that an increase in the amount of Atg11 at the PAS enhances the recruitment of Atg8 and Atg9 to this site and facilitates the formation of more cytoplasm-to-vacuole targeting vesicles. In response to autophagy induction, the amount of most Atg proteins remains unchanged at the PAS, whereas we see an enhanced recruitment of Atg8 and 9 at this site. During autophagy, the amount of Atg8 at the PAS showed a periodic change, indicating the formation of autophagosomes. Application of this method and further analysis will provide more insight into the functions of Atg proteins.
authors.affiliation: Life Sciences Institute and Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Jiefei
authors.initials: J
authors.lastname: Geng
authors.forename: Misuzu
authors.initials: M
authors.lastname: Baba
authors.forename: Usha
authors.initials: U
authors.lastname: Nair
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Klionsky
mesh_terms: D001343:Autophagy; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007700:Kinetics; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins