Gα12 overexpression induced by miR-16 dysregulation contributes to liver fibrosis by promoting autophagy in hepatic stellate cells.

Abstract

BACKGROUND & AIMS:

Hepatic stellate cells (HSCs) have a role in liver fibrosis. Guanine nucleotide-binding α-subunit 12 (Gα12) converges signals from G-protein-coupled receptors whose ligand levels are elevated in the environment during liver fibrosis; however, information is lacking on the effect of Gα12 on HSC trans-differentiation. This study investigated the expression of Gα12 in HSCs and the molecular basis of the effects of its expression on liver fibrosis.

METHODS:

Gα12 expression was assessed by immunostaining, and immunoblot analyses of mouse fibrotic liver tissues and primary HSCs. The role of Gα12 in liver fibrosis was estimated using a toxicant injury mouse model with Gα12 gene knockout and/or HSC-specific Gα12 delivery using lentiviral vectors, in addition to primary HSCs and LX-2 cells using microRNA (miR) inhibitors, overexpression vectors, or adenoviruses. miR-16, Gα12, and LC3 were also examined in samples from patients with fibrosis.

RESULTS:

Gα12 was overexpressed in activated HSCs and fibrotic liver, and was colocalised with desmin. In a carbon tetrachloride-induced fibrosis mouse model, Gα12 ablation prevented increases in fibrosis and liver injury. This effect was attenuated by HSC-specific lentiviral delivery of Gα12. Moreover, Gα12 activation promoted autophagy accompanying c-Jun N-terminal kinase-dependent ATG12-5 conjugation. In addition, miR-16 was found to be a direct inhibitor of the de novo synthesis of Gα12. Modulations of miR-16 altered autophagy in HSCs. In a fibrosis animal model or patients with severe fibrosis, miR-16 levels were lower than in their corresponding controls. Consistently, cirrhotic patient liver tissues showed Gα12 and LC3 upregulation in desmin-positive areas.

CONCLUSIONS:

miR-16 dysregulation in HSCs results in Gα12 overexpression, which activates HSCs by facilitating autophagy through ATG12-5 formation. This suggests that Gα12 and its regulatory molecules could serve as targets for the amelioration of liver fibrosis.

LAY SUMMARY:

Guanine nucleotide-binding α-subunit 12 (Gα12) is upregulated in activated hepatic stellate cells (HSCs) as a consequence of the dysregulation of a specific microRNA that is abundant in HSCs, facilitating the progression of liver fibrosis. This event is mediated by c-Jun N-terminal kinase-dependent ATG12-5 formation and the promotion of autophagy. We suggest that Gα12 and its associated regulators could serve as new targets in HSCs for the treatment of liver fibrosis.

• Authors: Kyu Min Kim, Chang Yeob Han, Ji Young Kim, Sam Seok Cho, Yun Seok Kim, Ja Hyun Koo, Jung Min Lee, Sung Chul Lim, Keon Wook Kang, Jae-Sung Kim, Se Jin Hwang, Sung Hwan Ki, Sang Geon Kim
• Journal: Journal of hepatology (J Hepatol) Vol. 68 Issue 3 Pg. 493-504 (03 2018) ISSN: 1600-0641 [Electronic] Netherlands
• PMID: 29080810 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2017 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Chemical References

• MIRN16 microRNA, human
• MicroRNAs
• Mirn16 microRNA, mouse
• Plasminogen Activator Inhibitor 1
• Serine Proteinase Inhibitors
• GTP-Binding Protein alpha Subunits, G12-G13

Topics

• Animals
• Autophagy (drug effects)
• Cell Proliferation (drug effects)
• GTP-Binding Protein alpha Subunits, G12-G13 (antagonists & inhibitors, metabolism)
• Gene Expression Regulation
• Hepatic Stellate Cells (metabolism)
• Humans
• Liver Cirrhosis (metabolism, pathology)
• Mice
• MicroRNAs (metabolism)
• Plasminogen Activator Inhibitor 1 (metabolism, pharmacology)
• Serine Proteinase Inhibitors (pharmacology)
• Signal Transduction (drug effects)
• Up-Regulation