title: Dissection of ubiquitinated protein degradation by basal autophagy.
abstract: Basal autophagy plays an essential role as a protein quality control system. Although it has been demonstrated that the loss of autophagy results in the accumulation of ubiquitin-positive aggregates and the development of neurodegenerative diseases, the precise autophagy substrate(s) remain unclear. Here, we determined whether ubiquitinated proteins are direct substrates for basal autophagy using a fluorescent ratiometric probe for ubiquitin. We show that the degradation of polyubiquitinated proteins is not dependent on basal autophagy. Although ubiquitin-positive aggregates are observed in autophagy knockout cultured cells, the aggregates consist of soluble and mobile polyubiquitinated proteins, which are trapped by p62 without an increase in the total amount of ubiquitinated proteins. These results suggest that ubiquitinated proteins are not major targets for basal autophagy.
authors.affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Takayama
authors.affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuura
authors.affiliation: Department of Nanobiology, Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Japan.
authors.forename: Eisuke
authors.initials: E
authors.lastname: Itakura
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism; D001343:Autophagy; D000071183:Autophagy-Related Proteins / Q000235:genetics / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D025821:Polyubiquitin / Q000378:metabolism*; D059748:Proteolysis; D034622:RNA Interference; D000071456:Sequestosome-1 Protein / Q000235:genetics / Q000378:metabolism; D057149:Ubiquitinated Proteins / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: C539000:ATG14 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D000071183:Autophagy-Related Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D057149:Ubiquitinated Proteins; D025821:Polyubiquitin
keywords: aggregates; autophagy; p62/sqstm1; protein degradation