Ubiquitin C-terminal hydrolase 1: A novel functional marker for liver myofibroblasts and a therapeutic target in chronic liver disease.
OBJECTIVE
Ubiquitination is a reversible protein modification involved in the major cellular processes that define cell phenotype and behaviour. Ubiquitin modifications are removed by a large family of proteases named deubiquitinases. The role of deubiquitinases in hepatic stellate cell (HSC) activation and their contribution to fibrogenesis are poorly defined. We have identified that the deubiquitinase ubiquitin C-terminal hydrolase 1 (UCHL1) is highly induced following HSC activation, determined its function in activated HSC and its potential as a therapeutic target for fibrosis.


METHODS
Deubiquitinase expression was determined in day 0 and day 10 HSC. Increased UCHL1 expression was confirmed in human HSC and in an alcoholic liver disease (ALD) patient liver. The importance of UCHL1 in hepatic fibrosis was investigated in CCl4 and bile duct ligation injured mice using a pharmacological inhibitor (LDN 57444). The effects of UCHL1 inhibition on HSC proliferation were confirmed by Western blot and 3H thymidine incorporation.


RESULTS
Here we report that pharmacological inhibition of UCHL1 blocks progression of established fibrosis in CCl4 injured mice. UCHL1 siRNA knockdown, LDN 57444 treatment, or HSC isolated from UCHL1(-/-) mice show attenuated proliferation in response to the mitogen, platelet-derived growth factor. Additionally, we observed changes in the phosphorylation of the cell cycle regulator retinoblastoma protein (Rb) in the absence of UCHL1 highlighting a potential mechanism for the reduced proliferative response.


CONCLUSIONS
UCHL1 expression is highly upregulated upon HSC activation and is involved in the regulation of HSC proliferation. This study highlights therapeutic opportunities for pharmacological targeting of UCHL1 in chronic liver disease.
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Caroline L
CL
Wilson
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Lindsay B
LB
Murphy
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Jack
J
Leslie
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Stuart
S
Kendrick
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Jeremy
J
French
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Christopher R
CR
Fox
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Neil S
NS
Sheerin
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Andrew
A
Fisher
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
John H
JH
Robinson
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Dina G
DG
Tiniakos
Ottawa Hospital Research Institute, 501 Smyth Rd, Ottawa K1H 8L6, Canada.
Douglas A
DA
Gray
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
Fiona
F
Oakley
Institute of Cellular Medicine, Faculty of Medical Sciences, 4th Floor, William Leech Building, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK. Electronic address: derek.mann@ncl.ac.uk.
Derek A
DA
Mann
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002251:Carbon Tetrachloride / Q000633:toxicity; D049109:Cell Proliferation; D054338:Cell Transdifferentiation; D002478:Cells, Cultured; D002908:Chronic Disease; D055785:Gene Knockdown Techniques; D055166:Hepatic Stellate Cells / Q000201:enzymology / Q000473:pathology; D006801:Humans; D008106:Liver Cirrhosis, Experimental / Q000201:enzymology / Q000473:pathology; D008107:Liver Diseases / Q000201:enzymology* / Q000473:pathology / Q000628:therapy; D008108:Liver Diseases, Alcoholic / Q000201:enzymology / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D058628:Myofibroblasts / Q000201:enzymology / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D043222:Ubiquitin Thiolesterase / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D064570:Ubiquitin-Specific Proteases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination
D015415:Biomarkers; D012333:RNA, Messenger; C482860:UCHL1 protein, human; D002251:Carbon Tetrachloride; C489034:UCHL1 protein, rat; D043222:Ubiquitin Thiolesterase; D064570:Ubiquitin-Specific Proteases; C496976:Uchl1 protein, mouse
Deubiquitinase; HSC; LDN57444; Liver fibrosis; UCHL1