Selected contribution: regulatory pathways involved in mechanical induction of c-fos gene expression in bone cells.
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 four-point 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-Gly-Asp peptides during loading did not inhibit the response, whereas addition of beta(1)-integrin antibodies inhibited the load response. The role of Ca(2+) signaling has been demonstrated by blocking upregulation with addition of 2 mM EGTA, which chelates extracellular Ca(2+), and gadolinium (10 microM), which inhibits stretch-activated channels. Addition of the Ca(2+) ionophore A-23187 induced upregulation without loading; however, addition of nifedipine (10 microM), 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(2+) signaling pathways and integrin binding in the c-fos response to mechanical strain.
Peake
M A
MA
Centre for Science and Technology in Medicine, School of Postgraduate Medicine, Keele University, North Staffordshire Hospital, Stoke on Trent ST4 7QB, United Kingdom.
Cooling
L M
LM
Magnay
J L
JL
Thomas
P B
PB
El Haj
A J
AJ
D001842:Bone and Bones / Q000166:cytology / Q000502:physiology; D020013:Calcium Signaling / Q000502:physiology; D002460:Cell Line; D003599:Cytoskeleton / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D016762:Genes, fos / Q000235:genetics*; D006801:Humans; D016023:Integrins / Q000502:physiology; D013314:Stress, Mechanical; D015854:Up-Regulation
D016023:Integrins