herbimycin and Osteopetrosis

Mice carrying homozygous disruption of the c-src proto-oncogene (Src-/-) develop osteopetrosis due to an impaired ability of osteoclasts to adhere to the bone surface and/or to form bone-resorbing ruffled border. It has also been reported that osteopontin (OPN), a secreted phosphoprotein, mediates osteoclast adherence to the bone matrix. We report here that cells from Src-/- mice, both in vitro and in vivo, express OPN mRNA and protein at a significantly reduced level as compared to cells from Src+/- and +/+ animals, suggesting a potential role for the proto-oncogene c-src in the regulation of OPN gene expression. Our data also show that OPN gene expression can be induced by treatment of SR-/- cells with epidermal growth factor (EGF) and 12-O-tetradecanoyl phorbol-13-acetate (TPA). Results obtained from studies using inhibitors of receptor tyrosine kinases (RTKs) and protein kinase C (PKC) suggest that PKC and RTK are positioned in a pathway with PKC as the downstream effector for the EGF-induced OPN gene expression in SRC-/- cells, and that pp60c-src and EGF may regulate OPN gene expression through a common signalling pathway. Furthermore, contrary to published reports, our study shows that EGF-mediated cell signalling does not require functional interaction between the EGF-receptor and pp60c-src.

Topics: 3T3 Cells; Animals; Base Sequence; Benzoquinones; Bone and Bones; Cell Adhesion; Cell Line; DNA Primers; DNA Replication; Epidermal Growth Factor; ErbB Receptors; Gene Expression; Homozygote; Lactams, Macrocyclic; Mice; Microscopy, Electron; Molecular Sequence Data; Osteopetrosis; Osteopontin; Protein Kinase C; Proto-Oncogene Proteins pp60(c-src); Quinones; Rifabutin; Sialoglycoproteins; Tetradecanoylphorbol Acetate