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Characterization of 57 kDa statin as a true marker for growth arrest in tissue by its disappearance from regenerating liver
Author(s) -
Sandig Martin,
Bissonnette Robert,
Liu Catherine H. L.,
Tomaszewski George,
Wang Eugenia
Publication year - 1994
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041580210
Subject(s) - hepatocyte , cytoskeleton , western blot , cytoplasm , blot , microbiology and biotechnology , biology , immunofluorescence , nuclear protein , cell culture , antibody , cell cycle , cell , biochemistry , immunology , in vitro , genetics , transcription factor , gene
Statin, a 57 kDa nuclear protein, is lost from quiescent fibroblasts in culture when they are induced to enter the cell cycle by feeding with growth factors, or by removal of contact inhibition. In order to investigate changes in statin expression during the transition from a quiescent to a cycling state in situ, we performed 70% partial hepatectomy on rats and analyzed the regenerating liver by immunofluorescence microscopy with antistatin monoclonal antibodies (S44 mAb), and by immunoblotting of liver proteins in cytoplasmic and enriched nuclear/cytoskeletal fractions. Western blot analysis showed that rat hepatocytes in situ contain a nuclear 57 kDa form of statin, as seen in cultured fibroblasts; however additional S44‐immunoreactive polypeptides with molecular weights of 53 and 110 kDa are also present in both cytoplasmic and nuclear/cytoskeletal fractions. Immunofluo‐rescence microscopy indicates that the proportion of S44‐positive hepatocyte nuclei drops to ∼60% within 24 hours after hepatectomy, a time period when re‐entry of hepatocytes into the cell cycle is first observed. On Western blots of hepatocyte nuclear/cytoskeletal proteins obtained 24 hours after hepatectomy, the 57 kDa form of statin is markedly reduced. These results suggest that, although in liver the S44 antibody recognizes three proteins (53 kDa, 57 kDa, and 110 kDa), the 57 kDa in intact liver, similar to cultured fibroblasts, is the only polypeptide recognized by the statin antibody that disappears when hepatocytes are induced to re‐enter the cell cycle from a quiescent state. © 1994 Wiley‐Liss, Inc.