Related Experiment Video
Updated: May 28, 2025

Exploring the Regulation of Lipid Droplet Catabolism through Lipophagy
Published on: January 31, 2025
The Greatwall kinase Rim15 promotes microautophagy and microlipophagy under the control of TORC1
Yuka Takahashi1, Trieu Tu San2, Md Imran Nur Manik3
1Course of Biological Science, Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, 422-8021, Japan.
Abstract:
Atg1/ULK1 protein kinase induces macroautophagy, but not microautophagy, after nutrient starvation and inactivation of target of rapamycin complex 1 (TORC1) protein kinase. Microautophagy is also induced by TORC1 inactivation, but a TORC1-downstream protein kinase responsible for microautophagy induction remains obscure. Here, we show that the Greatwall kinase Rim15, a downstream protein kinase of TORC1, promotes bulk microautophagy induction after TORC1 inactivation. In addition, Rim15 was required for proper induction of microlipophagy (microautophagic degradation of lipid droplet). Endosomal sorting complex required for transport (ESCRT) machinery is recruited onto the vacuolar membrane after TORC1 inactivation for microautophagy. Loss of Rim15 reduced protein levels of subunits (Vps27 and Hse1) of ESCRT-0, a primary ESCRT subcomplex. Consistently, the recruitment of ESCRT-0 onto the vacuolar membrane after rapamycin was reduced in rim15Δ cells. On the other hand, Rim15 was dispensable for ESCRT function in multivesicular body formation. This study reveals that Rim15 specifically regulates function of ESCRT-0 in microautophagy under the control of TORC1 and provides a new insight into lipophagy-related human diseases.
Related Concept Videos
mTOR Signaling and Cancer Progression
The mTOR pathway or the...
PI3K/mTOR/AKT Signaling Pathway
Delivery Pathways to the Lysosome
Endocytosis
In endocytosis, the cell membrane takes up macromolecules and particles from the surrounding medium. Clathrin-mediated...
Autophagy
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
Autophagic Cell Death
Autophagy and Apoptosis
Autophagy can activate apoptosis. In normal conditions, the autophagy activating protein Beclin-1 and...
Destabilization of Microtubules

