Transglutaminase induced by epidermal growth factor negatively regulates the growth signal in primary cultured hepatocytes.
Transglutaminase (TGase) activity increased 2.5-fold at 6 h after treatment of rat hepatocytes with 17 nM epidermal growth factor (EGF). In the same manner, putrescine incorporation into the proteins of cells occurred in EGF-treated cells, but not in those pretreated with monodansylcadaverine (MDC), a TGase inhibitor, even in the presence of EGF. These results suggest that EGF-induced TGase was active and catalysed some cross-linkage reaction. Cycloheximide completely blocked the increase in TGase activity induced by EGF, suggesting that EGF stimulated de novo synthesis of TGase within 6 h. Furthermore, Northern blotting analysis indicated that EGF increased the expression of TGase mRNA. Pretreatment of cells with MDC additionally increased EGF-induced DNA-synthesis and the ratio of cells in S-phase. TGase antisense oligonucleotide inhibited de novo synthesis of TGase, resulting in increases in the ratios of S- and G2/M-phase cells in the presence of EGF. This effect was the result of inhibition of EGF-induced down-regulation of high-affinity receptor expression. These results suggest that the EGF-induced increase in TGase activity is a negative regulator of a growth signal in rat hepatocytes.
Radioisotope Research Institute, Faculty of Medicine, University of Tokyo, Japan.
S
S
Katoh
N
N
Nakagawa
Y
Y
Yano
K
K
Satoh
H
H
Kohno
Y
Y
Ohkubo
D000818:Animals; D001483:Base Sequence; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D011503:Transglutaminases / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*
D004791:Enzyme Inhibitors; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D004815:Epidermal Growth Factor; D011503:Transglutaminases; D066246:ErbB Receptors; C008542:monodansylcadaverine; D002103:Cadaverine