In vivo analysis of autophagy in response to nutrient starvation using transgenic mice expressing a fluorescent autophagosome marker.
Macroautophagy mediates the bulk degradation of cytoplasmic components. It accounts for the degradation of most long-lived proteins: cytoplasmic constituents, including organelles, are sequestered into autophagosomes, which subsequently fuse with lysosomes, where degradation occurs. Although the possible involvement of autophagy in homeostasis, development, cell death, and pathogenesis has been repeatedly pointed out, systematic in vivo analysis has not been performed in mammals, mainly because of a limitation of monitoring methods. To understand where and when autophagy occurs in vivo, we have generated transgenic mice systemically expressing GFP fused to LC3, which is a mammalian homologue of yeast Atg8 (Aut7/Apg8) and serves as a marker protein for autophagosomes. Fluorescence microscopic analyses revealed that autophagy is differently induced by nutrient starvation in most tissues. In some tissues, autophagy even occurs actively without starvation treatments. Our results suggest that the regulation of autophagy is organ dependent and the role of autophagy is not restricted to the starvation response. This transgenic mouse model is a useful tool to study mammalian autophagy.
Mizushima
Noboru
N
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Yamamoto
Akitsugu
A
Matsui
Makoto
M
Yoshimori
Tamotsu
T
Ohsumi
Yoshinori
Y
D000818:Animals; D001343:Autophagy / Q000502:physiology*; D000071190:Autophagy-Related Protein 8 Family; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D008869:Microtubule-Associated Proteins / Q000235:genetics; D010588:Phagosomes / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D013217:Starvation; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D014617:Vacuoles / Q000378:metabolism*
C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins