Universität zu Köln

Matthias, Jan, Messling, Susanne and Eichinger, Ludwig ORCID: 0000-0003-1594-6117 (2016). The two Dictyostelium autophagy eight proteins, ATG8a and ATG8b, associate with the autophagosome in succession. Eur. J. Cell Biol., 95 (1). S. 15 - 26. MUNICH: ELSEVIER GMBH. ISSN 1618-1298

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Abstract

Autophagy is an ancient cellular pathway that is conserved from yeast to man. It contributes to many physiological and pathological processes and plays a major role in the degradation of proteins and/or organelles in response to starvation and stress. In the autophagic process cytosolic material is captured into double membrane-bound vesicles, the autophagosomes. After fusion with lysosomes, the cargo is degraded in the generated autolysosomes and then recycled for further use. Autophagy 8 (ATG8, in mammals LC3), a well-established marker of autophagy, is covalently linked to phosphatidylethanolamine on the autophagic membrane during autophagosome formation. Bioinformatic analysis of the Dictyostelium genome revealed two atg8 genes which encode the ATG8a and ATG8b paralogs. They are with around 14 kDa similar in size, 54 % identical to one another and more closely related to the corresponding proteins in fungi and plants than in animals. For ATG8a we found a strong up-regulation throughout the 24 h developmental time course while ATG8b expression was highest in vegetative cells followed by a moderate reduction during early development. Confocal microscopy of fluorescently tagged ATG8a and ATG8b in vegetative AX2 wild-type and in ATG9(-) cells showed that both proteins mainly co-localized on vesicular structures with a diameter above 500 nm while those smaller than 500 nm were predominantly positive for ATG8b. In ATG9(-) cells we found a strong increase in the relative abundance of ATG8a-positive large vesicular structures and of total ATG8b-positive structures per cell indicating autophagic flux problems in this mutant. We also found that vesicular structures positive for ATG8a and/or ATG8b were also positive for ubiquitin. Live cell imaging of AX2 and ATG9- cells co-expressing combinations of red and green tagged ATG8a, ATG8b or ATG9 revealed transient co localizations of these proteins. Our results suggest that ATG8b associates with nascent autophagosomes before ATG8a. We further find that the process of autophagosome formation in Dictyostelium is highly dynamic. We infer from our data that Dictyostelium ATG8a and ATG8b have distinct functions in autophagosome formation and that ATG8b is the functional orthologue of the mammalian LC3 subfamily and ATG8a of the GABARAP subfamily. (C) 2015 The Authors. Published by Elsevier GmbH.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Matthias, Jan UNSPECIFIED UNSPECIFIED UNSPECIFIED Messling, Susanne UNSPECIFIED UNSPECIFIED UNSPECIFIED Eichinger, Ludwig UNSPECIFIED orcid.org/0000-0003-1594-6117 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-292627
DOI:	10.1016/j.ejcb.2015.10.007
Journal or Publication Title:	Eur. J. Cell Biol.
Volume:	95
Number:	1
Page Range:	S. 15 - 26
Date:	2016
Publisher:	ELSEVIER GMBH
Place of Publication:	MUNICH
ISSN:	1618-1298
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SELECTIVE AUTOPHAGY; LIR MOTIF; UBIQUITIN; MEMBRANE; LC3; BIOGENESIS; MUTANTS; MACROAUTOPHAGY; TRAFFICKING; DEGRADATION Multiple languages Cell Biology Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/29262