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Impaired liver regeneration in mice lacking methionine adenosyltransferase 1A
Author(s) -
Chen Lixin,
Zeng Ying,
Yang Heping,
Lee Taunia D.,
French Samuel W.,
Corrales Fernando J.,
García-Trevijano Elena R.,
Avila Matías A.,
Mato José M.,
Lu Shelly C.
Publication year - 2004
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.03-1204fje
Subject(s) - kinase , biology , liver regeneration , mapk/erk pathway , knockout mouse , cyclin d1 , endocrinology , gene knockout , signal transduction , medicine , microbiology and biotechnology , cell cycle , biochemistry , regeneration (biology) , apoptosis , receptor , gene
ABSTRACT Methionine adenosyltransferase (MAT) is an essential enzyme because it catalyzes the formation of S‐adenosylmethionine (SAMe), the principal biological methyl donor. Of the two genes that encode MAT, MAT1A is mainly expressed in adult liver and MAT2A is expressed in all extrahepatic tissues. Mice lacking MAT1A have reduced hepatic SAMe content and spontaneously develop hepatocellular carcinoma. The current study examined the influence of chronic hepatic SAMe deficiency on liver regeneration. Despite having higher baseline hepatic staining for proliferating cell nuclear antigen, MAT1A knockout mice had impaired liver regeneration after partial hepatectomy (PH) as determined by bromodeoxyuridine incorporation. This can be explained by an inability to up‐regulate cyclin D1 after PH in the knockout mice. Upstream signaling pathways involved in cyclin D1 activation include nuclear factor κB (NFκB), the c‐Jun‐N‐terminal kinase (JNK), extracellular signal‐regulated kinases (ERKs), and signal transducer and activator of transcription‐3 (STAT‐3). At baseline, JNK and ERK are more activated in the knockouts whereas NFκB and STAT‐3 are similar to wild‐type mice. Following PH, early activation of these pathways occurred, but although they remained increased in wild‐ type mice, c‐jun and ERK phosphorylation fell progressively in the knockouts. Hepatic SAMe levels fell progressively following PH in wild‐type mice but remained unchanged in the knockouts. In culture, MAT1A knockout hepatocytes have higher baseline DNA synthesis but failed to respond to the mitogenic effect of hepatocyte growth factor. Taken together, our findings define a critical role for SAMe in ERK signaling and cyclin D1 regulation during regeneration and suggest chronic hepatic SAMe depletion results in loss of responsiveness to mitogenic signals.