Comparison of the Function of the βC and βE Subunits of Activin in AML12 Hepatocytes

• Published in: Endocrine Journal Vol. 52; no. 2; pp. 169 - 175
• Main Authors: WADA, Wataru, MEDINA, Johan J., KUWANO, Hiroyuki, KOJIMA, Itaru
• Format: Journal Article
• Language: English
• Published: The Japan Endocrine Society 01.04.2005
• Subjects: Activin; Growth; Heterodimer; Liver
• ISSN: 0918-8959; 1348-4540
• DOI: 10.1507/endocrj.52.169

To investigate the function of the βC and βE subunits of activin, we overexpressed these subunits in AML12 cells, a normal hepatocyte cell line, using adenovirus vector. Overexpression of the βC subunit increased [3H]thymidine incorporation and the cell number. In contrast, both [3H]thymidine incorporation and the cell number were reduced in the βE overexpressing cells. When AML cells overexpressing the βE subunit were cultured in medium containing 1% serum for 48 h, many of the cells died by apoptosis, whereas cells overexpressing the βC subunit or β-galactosidase survived in the same condition. To examine dimer formation, the βC and βE subunits were expressed in AML12 cells. In these cells, the βC homodimer, the βE homodimer and the βC-βE heterodimer were detected. When the expression level of the βE subunit was increased, formation of the βE homodimer was increased, while formation of the βC-βE heterodimer was slightly reduced. Overexpression of the βE subunit did not significantly affect the formation of the βC homodimer. These results indicate that the βC and βE subunits form homo- and heterodimers, and that the functions of the two subunits are quite different.