Hepatic Stellate Cell Selective Disruption of Dynamin-2 GTPase Increases Murine Fibrogenesis through Up-Regulation of Sphingosine-1 Phosphate-Induced Cell Migration.

Abstract

Dynamin-2 (Dyn2) is implicated in endocytosis of receptor tyrosine kinases, which contribute to hepatic stellate cell (HSC) activation and liver fibrosis. A point mutation converting lysine 44 of Dyn2 to alanine (Dyn2K44A) disrupts its GTPase activity. We hypothesized that Dyn2K44A expression in HSCs would decrease HSC activation and fibrogenesis in vivo by disrupting receptor tyrosine kinase endocytosis and signaling. Dyn2K44Afl/fl mice were crossed with Collagen1-Cre (Col1Cre) mice to generate offspring with HSC selective expression of Dyn2K44A (Col1Cre/Dyn2K44Afl/fl). Contrary to our hypothesis, Col1Cre/Dyn2K44Afl/fl mice showed increased hepatic fibrosis in response to liver injury. To elucidate mechanisms, we conducted in vitro experiments with HSCs infected with adenoviral vectors encoding LacZ, Dyn2K44A, or Dyn2WT. HSC-expressing Dyn2K44A displayed increased mRNA and protein levels of sphingosine kinase-1 (SK1), an enzyme previously implicated in the pathogenesis of fibrosis. To study the functional effects of Dyn2K44A regulation of SK1, we examined effects of AKT signaling and migration in HSCs. Dyn2K44A promoted both AKT phosphorylation and HSC migration in an SK1-dependent manner. Genetic disruption of Dyn2 GTPase activity selectively in HSC enhances fibrogenesis, driven at least in part through up-regulation of the SK1 pathway and cell migration in HSCs.

• Authors: Ruisi Wang, Qian Ding, Thiago M De Assuncao, Taofic Mounajjed, Jessica L Maiers, Changwei Dou, Sheng Cao, Usman Yaqoob, Robert C Huebert, Vijay H Shah
• Journal: The American journal of pathology (Am J Pathol) Vol. 187 Issue 1 Pg. 134-145 (Jan 2017) ISSN: 1525-2191 [Electronic] United States
• PMID: 27840081 (Publication Type: Journal Article)
• Copyright: Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

Chemical References

• Collagen Type I
• Lysophospholipids
• Mutant Proteins
• sphingosine 1-phosphate
• Carbon Tetrachloride
• Phosphotransferases (Alcohol Group Acceptor)
• sphingosine kinase
• Proto-Oncogene Proteins c-akt
• Dynamin II
• Sphingosine

Topics

• Animals
• Bile Ducts (metabolism, pathology)
• Carbon Tetrachloride
• Cell Movement (drug effects)
• Collagen Type I (metabolism)
• Dynamin II (metabolism)
• Hepatic Stellate Cells (enzymology, pathology)
• Ligation
• Liver Cirrhosis (enzymology, pathology)
• Lysophospholipids (pharmacology)
• Mice
• Mutant Proteins (metabolism)
• Phosphotransferases (Alcohol Group Acceptor) (metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• Signal Transduction (drug effects)
• Sphingosine (analogs & derivatives, pharmacology)
• Up-Regulation (drug effects)