Background: Macroautophagy (or autophagy) is a conserved degradative pathway that breaks down sequestered cytoplasmic proteins and organelles in specialized double-membrane compartments called autophagosomes that fuse with lysosomes. Several proteins orchestrate this process, specifically Rab GTPases that are master regulators of molecular trafficking. RAB18 GTPase, a known mediator of stellate cell activation, is known to modulate autophagic flux in fibroblasts. However, its role in autophagy is unexplored in hepatic stellate cells.
Objective: The aim of this study was to investigate the role of RAB18 in modulating autophagy in hepatic stellate cells.
Methods: Role of RAB18 was determined by genetic depletion, pharmacologic inhibition, and overexpression studies to monitor autophagy flux and proteostasis in human LX2 stellate cell line.
Results: RAB18 knockdown increases autophagy flux and regulates proteostasis. LX2 cells stimulated with transforming growth factor-beta robustly increases expression of profibrotic genes such as COL1A1 and ACTA2 along with RAB18 and its guanine nucleotide exchange factor, RAB3GAP1.
Conclusion: The study elucidates a role for RAB18 in autophagy and regulation of proteostasis in human stellate cells. Molecular insights into this process can provide therapeutic opportunities for intervention in liver fibrosis.
Keywords: Autophagy; Bafilomycin; Canavanine; Fibrosis; Hepatic stellate cells; LC3-II; RAB18.
Copyright © 2019 National Lipid Association. Published by Elsevier Inc. All rights reserved.