Detection of thymopoietin-responsive proteins in nude mouse spleen cells by two-dimensional polyacrylamide gel electrophoresis and image processing.

Lymphoid cells isolated from the spleen of BALB/c nu/nu nude mice were treated with synthetic human thymopoietin, and newly synthesized proteins were labeled by [35S]methionine incorporation. In the control experiment, the same lot of spleen cells were incubated in the labeling medium without the addition of thymopoietin. Urea/detergent-soluble proteins were extracted from the cells after 3 h incubation to be separated by two-dimensional polyacrylamide gel electrophoresis. Spots of [35S]methionine-labeled proteins were visualized by autoradiography and analyzed by image processing. The computer-aided spot matching screened out three major thymopoietin-responsive proteins, TRP-1, −2 and −3. [35S]Methionine incorporation into TRP-3, of which the isoelectric point and molecular mass were approximately pI5 and 10 kDa, respectively, was decreased by the thymopoietin treatment. In contrast with the down regulation, TRP-1, which was slightly higher in pI and slightly larger in molecular mass, and TRP-2, which was slightly higher in pI and almost the same in molecular mass as TRP-3, were evidently induced by the treatment. However, TRPs could not be assigned to Thy-1 antigen on the difference in molecular mass. The specific induction by the thymopoietin treatment suggested that TRP-1 and −2 might be novel proteins related to the intracellular signal transduction.