Cellular Responses to Mechanical Stress Selected Contribution: Regulatory pathways involved in mechanical induction of c-fos gene expression in bone cells

Peake, M. A., L. M. Cooling, J. L. Magnay, P. B. M. Thomas, and A. J. El Haj. Selected Contribution: Regulatory pathways involved in mechanical induction of c-fos gene expression in bone cells. J Appl Physiol 89: 2498–2507, 2000.—The regulatory pathways involved in the rapid response of the AP-1 transcription factor, c-fos, to mechanical load in human primary osteoblast-like (HOB) cells and the human MG-63 bone cell line were investigated using a fourpoint bending model. HOB and MG-63 cells showed upregulation of c-fos expression on fibronectin and collagen type I substrates; however, MG-63 cells did not respond on laminin YIGSR substrates. Addition of cytochalasin D and Arg-GlyAsp peptides during loading did not inhibit the response, whereas addition of b1-integrin antibodies inhibited the load response. The role of Ca signaling has been demonstrated by blocking upregulation with addition of 2 mM EGTA, which chelates extracellular Ca, and gadolinium (10 mM), which inhibits stretch-activated channels. Addition of the Ca ionophore A-23187 induced upregulation without loading; however, addition of nifedipine (10 mM), the L-type channel blocker, failed to prevent the load response. Inhibitors of downstream pathways indicated the involvement of protein kinase C. Our results demonstrate a key involvement of Ca signaling pathways and integrin binding in the c-fos response to mechanical strain.