Fig. 1

Continuous mechanical stretching of human periodontal ligament (hPDL) osteoblast-like cells enhances mitogen-activated protein kinase (MAPK) activity. Equivalent amounts of whole-cell lysates obtained from unstimulated (0) or mechanically stretched cells (for the indicated time in min) were subjected to in-gel kinase assays, in which bacterially expressed full-length c-Jun protein (left panel) or c-Fos protein (right panel) served as immobilized substrates in the presence of [γ-³²P]ATP and the respective kinase buffer. Kinases present in these cellular extracts that can phosphorylate c-Jun/c-Fos were identified by autoradiography of the washed and dried sodium dodecyl sulfate (SDS) polyacrylamide gel. Molecular masses of ¹⁴C-methylated protein standards (M) are indicated. The results are representative of three experiments using two different lysates.