Zhipeng Li1, Shaun G Weller2, Kristina Drizyte-Miller1, Jing Chen2, Eugene W Krueger2, Bridget Mehall2, Carol A Casey3, Hong Cao2, Mark A McNiven1,2,4. 1. Biochemistry and Molecular Biology Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN. 2. Center for Basic Research in Digestive Diseases, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN. 3. Department of Internal Medicine, University of Nebraska Medical Center, 988090 Nebraska Medical Center, Omaha, NE. 4. Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN.
Abstract
BACKGROUND AND AIMS: Hepatocytes play a central role in storage and utilization of fat by the liver. Selective breakdown of lipid droplets (LDs) by autophagy (also called lipophagy) is a key process utilized to catabolize these lipids as an energy source. How the autophagic machinery is selectively targeted to LDs, where it mediates membrane engulfment and subsequent degradation, is unclear. Recently, we have reported that two distinct GTPases, the mechanoenzyme, dynamin2 (Dyn2), and the small regulatory Rab GTPase, Rab10, work independently at distinct steps of lipophagy in hepatocytes. APPROACH AND RESULTS: In an attempt to understand how these proteins are regulated and recruited to autophagic organelles, we performed a nonbiased biochemical screen for Dyn2-binding partners and found that Dyn2 actually binds Rab10 directly through a defined effector domain of Rab10 and the middle domain of Dyn2. These two GTPases can be observed to interact transiently on membrane tubules in hepatoma cells and along LD-centric autophagic membranes. Most important, we found that a targeted disruption of this interaction leads to an inability of cells to trim tubulated cytoplasmic membranes, some of which extend from lipophagic organelles, resulting in LD accumulation. CONCLUSIONS: This study identifies a functional, and direct, interaction between Dyn2 and a regulatory Rab GTPase that may play an important role in hepatocellular metabolism.
BACKGROUND AND AIMS: Hepatocytes play a central role in storage and utilization of fat by the liver. Selective breakdown of lipid droplets (LDs) by autophagy (also called lipophagy) is a key process utilized to catabolize these lipids as an energy source. How the autophagic machinery is selectively targeted to LDs, where it mediates membrane engulfment and subsequent degradation, is unclear. Recently, we have reported that two distinct GTPases, the mechanoenzyme, dynamin2 (Dyn2), and the small regulatory Rab GTPase, Rab10, work independently at distinct steps of lipophagy in hepatocytes. APPROACH AND RESULTS: In an attempt to understand how these proteins are regulated and recruited to autophagic organelles, we performed a nonbiased biochemical screen for Dyn2-binding partners and found that Dyn2 actually binds Rab10 directly through a defined effector domain of Rab10 and the middle domain of Dyn2. These two GTPases can be observed to interact transiently on membrane tubules in hepatoma cells and along LD-centric autophagic membranes. Most important, we found that a targeted disruption of this interaction leads to an inability of cells to trim tubulated cytoplasmic membranes, some of which extend from lipophagic organelles, resulting in LD accumulation. CONCLUSIONS: This study identifies a functional, and direct, interaction between Dyn2 and a regulatory Rab GTPase that may play an important role in hepatocellular metabolism.
Authors: Brian Raught; John H Brumell; Kirsten C Boddy; Hongxian Zhu; Vanessa M D'Costa; Caishuang Xu; Ksenia Beyrakhova; Miroslaw Cygler; Sergio Grinstein; Etienne Coyaud; Estelle M N Laurent; Jonathan St-Germain Journal: Nat Commun Date: 2021-08-04 Impact factor: 14.919