This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Autophagy is an intracellular degradation mechanism in eukaryotes. The autophagosome, which encloses damaged or excess cellular material for degradation, is constructed from lipids supplied by the endoplasmic reticulum (ER) via the lipid transfer protein Atg2.
Researchers have identified an activation mechanism that enables Atg2 localization to the ER, facilitating efficient lipid transfer. This activation mechanism was found to be conserved across fungi and mammals and may be a crucial part of autophagosome formation. Autophagy is the process by which eukaryotic cells—plants, animals and fungi—remove damaged or superfluous cellular components.
"Upon induction of autophagy, a cup-shaped lipid membrane called the isolation membrane emerges in the cytoplasm, expands into a spherical structure while engulfing a portion of the cytoplasm, and finally closes to form an autophagosome," says Dr. Tetsuya Kotani, specially appointed lecturer at the Cell Biology Center, Institute of Integrated Research, Institute of Science Tokyo (Science Tokyo), Japan. The autophagy-related proteins (Atg in fungi, ATG in mammals) regulate autophagosome formation.
Several Atg proteins combine to form a pre-autophagosomal structure (PAS), which expands into the isolation membrane mediated by Atg1, a protein kinase. The PAS uses lipids from the endoplasmic reticulum (ER) to eventually form the autophagosome. This lipid transfer is mediated by Atg2.
However, the mechanism by which Atg2 identifies and docks to the ER membrane, and the regulation of its activity, are not well understood. Kotani and Professor Hitoshi Nakatogawa of the Cell Biology Center, Science Tokyo, together with specially appointed associate professor Akiko Kuma of the Graduate School of Medicine, The University of Osaka, discovered how Atg2 recognizes and binds to the ER. Their findings are published in Proceedings of the National Academy of Sciences.
The research team first studied Atg2 in the yeast Saccharomyces cerevisiae. They found that cytosolic Atg2 did not bind to the ER. Only after Atg2 localized to the PAS did it acquire the ability to bind to the ER.
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