Co-immunoprecipitation (Co IP) of Syp with insulin receptor substrate (IRS)-1 in normal and osteoarthitis (OA) osteoblasts. Cells were grown to confluence and incubated overnight in serum free medium. Cells were then exposed to 50 ng/ml insulin-like growth factor (IGF)-1 for various lengths of time, as indicated. After cell lysis in RIPA buffer and IP with an anti-IRS-1 antibody, co-immunoprecipitated Syp levels were visualized by immunoblotting with an anti-Syp antibody. A representative immunoblotting of three different experiments is presented. Determination of actin was used as the control for loading.