Fluid flow-induced tyrosine phosphorylation and participation of growth factor signaling pathway in osteoblast-like cells

✍ Scribed by Toshiko Ogata

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 246 KB
• Volume: 76
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(20000315)76:4<529::aid-jcb1>3.0.co;2-5

✦ Synopsis

To investigate how mechanical loading stimulates bone cells, we subjected murine osteoblast-like cells, MC3T3E1, to fluid flow generated by shaking culture dishes. Since we had previously found that egr-1 mRNA is up-regulated by the flow, and that the regulation involves tyrosine kinase, we examined which proteins are tyrosinephosphorylated by flow. Western blotting and immunoprecipitation of cell lysates showed tyrosine phosphorylation enhancement of many proteins, including ERK2 and Shc, and activation of ERK1/2. Although these responses did not occur in serum-free media, addition of EGF or bFGF recovered the responses. AG1478, an inhibitor of EGF receptor kinase activity, abolished tyrosine phosphorylation enhancement, ERK1/2 activation, and egr-1 mRNA accumulation induced by the flow of EGF-containing serum-free media. These results suggest that growth factor signaling pathways are involved in these responses. Repetition of fluid flow induced repeatedly up-regulation of egr-1 mRNA. Such events may also occur in bone under mechanical loading.