Title:
Autophagic degradation of the nucleus and the endoplasmic reticulum
Speaker:
Hitoshi Nakatogawa
School of Life Science and Technology, Tokyo Institute of Technology
Abstract:
Autophagy mediates degradation of intracellular material in lysosomes or vacuoles (1). While autophagy non-selectively degrades portion of the cytoplasm under starvation conditions, an increasing number of proteins or organelles have been shown to be degraded by autophagy in a selective manner. Autophagy receptors play central roles in target selection in selective autophagy. These proteins bind to specific targets, and also bind to Atg8 on forming autophagosomal membranes, leading to the efficient sequestration of the targets into autophagosomes. Recent studies revealed that some organelles such as mitochondria and peroxisomes are degraded by selective autophagy, and that these processes are linked to human diseases.
We recently discovered two novel autophagy receptors, Atg39 and Atg40, in the budding yeast Saccharomyces cerevisiae (2). Atg39 localizes to the nuclear envelope, and allows autophagosomes to sequester part of the nucleus (double membrane vesicles) via the interaction with Atg8. On the other hand, Atg40 localizes to the endoplasmic reticulum (ER), and loads fragments of the ER into autophagosomes by binding to Atg8. In this seminar, I will briefly overview our current knowledge on these new selective autophagy pathways called “nucleophagy” and “ER-phagy” in yeast and other organisms including humans, and then discuss the mechanisms by which the nucleus and the ER are fragmented and sequestered into the autophagosome, based on our unpublished results.
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