Cell-cycle dependent phosphorylation of HSP28 by TGF beta 1 and H2O2 in normal mouse osteoblastic cells (MC3T3-E1), but not in their ras-transformants.
Transforming growth factor (TGF) beta 1 increased phosphorylation of a specific protein of approximately M(r) = 30,000 (p30) in mouse osteoblastic MC3T3-E1 cells. This protein, p30, was identified as one of the small heat shock proteins (HSP) 28 from the electrophoretic pattern on two-dimensional gels, and its peptide map compared with that of heat shock-inducible p28. The increase in phosphorylation of HSP 28 seemed to correlate with growth inhibition in this cell line, since it was increased by growth inhibitory agents, such as TGF beta 1, H2O2 and 12-O-tetradecanoylphorbol-13-acetate (TPA), but not by the growth stimulating agent, epidermal growth factor (EGF), and this phosphorylation was observed only when the cells were sensitive to growth inhibition by these agents, in the late G1 phase of the cell cycle. Furthermore, in ras-transformants, whose DNA synthesis was not inhibited by these agents, this phosphorylation was not increased by these stimuli. These results indicate that phosphorylation of HSP 28 may be coupled to inhibition of DNA synthesis in this cell line.
Shibanuma
M
M
Department of Cancer Cell Research, University of Tokyo, Japan.
Kuroki
T
T
Nose
K
K
D000818:Animals; D002472:Cell Transformation, Viral; D011905:Genes, ras; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology; D018125:Receptors, Transforming Growth Factor beta; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D006360:Heat-Shock Proteins; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D006861:Hydrogen Peroxide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate