Figure 9.

Comparison of the stability of TβRI protein between normal and scleroderma fibroblasts. Cells were incubated in cysteine- and methionine-free MEM for 30 minutes and then pulsed in the same medium containing [³⁵S]cysteine and [³⁵S]methionine (1 mCi/ml) for 30 minutes. Pulse-labeled cells were chased for 0, 3, or 6 hours in serum-free medium. Cell extracts (1 μg) were subjected to immunoprecipitation using anti-TβRI Ab, and immunoprecipitates (IP) were analyzed by SDS-PAGE and autoradiography. One representative of five independent experiments is shown (a). The densities of bands were measured with a densitometer, and the protein half-life was calculated as described in Methods. The mean and SEM from five separate experiments are shown (b).