title: c-fos reduces growth factor requirements for mitogenic stimulation of L6 rat myoblasts.
abstract: Addition of fetal calf serum (FCS) to serum-deprived L6J1 rat myoblasts increases fos-like immunoreactivity. The nuclear immunoreactivity reached a maximum 2 h after serum addition. Effects of the c-fos protein on myoblast proliferation were analyzed in L6J1 rat myoblasts transfected with the murine c-fos gene under control of a metallothionein promoter. L6J1 myoblasts with elevated expression of transfected c-fos reached higher cell densities than neo transfected control myoblasts when approaching a stationary phase in normal culture conditions (5% FCS). The differences in cell densities were even more pronounced at low serum concentrations (0.5% FCS). c-fos transfected cells also had a faster growth rate than did control cells in serum-free medium supplemented with calcium chloride, lithium chloride, sodium selenite, hydrocortisone, and insulin. The cell morphology of c-fos transfected L6J1 myoblasts was not affected compared to control myoblasts. These results suggest that c-fos protein expression in L6J1 myoblasts is activated by serum and that mitogenic stimulation of L6J1 myoblasts is facilitated by the presence of elevated amounts of c-fos protein.
authors.affiliation: Department of Medical Cell Genetics, Medical Nobel Institute, Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Rahm
authors.forename: T
authors.initials: T
authors.lastname: Sejersen
mesh_terms: D000818:Animals; D001769:Blood; D002452:Cell Count; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D006133:Growth Substances / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D008668:Metallothionein / Q000235:genetics; D009132:Muscles / Q000166:cytology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos; D051381:Rats; D014162:Transfection; D014168:Transferrin / Q000494:pharmacology
chemical_list: D006133:Growth Substances; D007328:Insulin; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D014168:Transferrin; D004247:DNA; D008668:Metallothionein