Glyceraldehyde-3-phosphate dehydrogenase exerts different biologic activities in apoptotic and proliferating hepatocytes according to its subcellular localization.
Recent evidences indicate new roles for the glycolytic protein glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in essential mammalian cell processes, such as apoptosis and proliferation. To clarify the involvement of this protein in growth and programmed cell death in the liver, cell models of hepatocytes in culture were used to study GAPDH expression, localization and enzymatic activity in hepatocyte proliferation and apoptosis. GAPDH expression in cell compartments was studied by Western blot. Nuclear expression of GAPDH increased in apoptosis, and cytoplasmic expression was elevated in apoptosis and proliferation. Subcellular localization was determined by GAPDH immunostaining and confocal microscopic analysis. Quiescent and proliferating hepatocytes showed cytoplasmic GAPDH, while apoptotic cells showed cytoplasmic but also some nuclear staining. The glycolytic activity of GAPDH was studied in nuclear and cytoplasmic cell compartments. GAPDH enzymatic activity increased in the nucleus of apoptotic cells and in cytoplasms of apoptotic and proliferating hepatocytes. Our observations indicate that during hepatocyte apoptosis GAPDH translocates to the nucleus, maintaining in part its dehydrogenase activity, and suggest that this translocation may play a role in programmed hepatocyte death. GAPDH over-expression and the increased enzymatic activity in proliferating cells, with preservation of its cytoplasmic localization, would occur in response to the elevated energy requirements of dividing hepatocytes. In conclusion, GAPDH plays different roles or biological activities in proliferating and apoptotic hepatocytes, according to its subcellular localization.
Barbini
Luciana
L
Departamento de Fisiologia, Facultad de Veterinaria, Universidad de Santiago de Compostela, Campus Universitario, 27002 Lugo, Spain. lbarbini@ffyb.uba.ar
Rodríguez
Joaquin
J
Dominguez
Fernando
F
Vega
Felix
F
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D006019:Glycolysis / Q000187:drug effects; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D053773:Transforming Growth Factor beta1; D017228:Hepatocyte Growth Factor; D003513:Cycloheximide; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases