Regulation of glycoprotein synthesis by thymic hormones in human thymocytes

The synthesis of glycoproteins was studied in human thymocytes by metabolic labeling of cells with [3H] fucose and the influence of two thymic hormones, thymopoietin and thymosin fraction V was examined. Membrane and cytoplasmic proteins were prepared by a differential centrifugation procedure and resolved into distinct bands by sodium dodecylsulfate-polyacrylamide gel electrophoresis. De novo synthesis of about 10 membrane proteins and 6 cytoplasmic proteins was observed. Four of the membrane proteins, M1 (98Kd), M2 (45Kd), M3 (42Kd) and M5 (25.5Kd), appear to be similar to the cell surface glycoproteins identified in human thymocytes by others [Eur. J. Immunol. 10: 359 (1980)]. M2 (45Kd protein) was synthesized in thymocytes treated with thymopoietin, in cells from a patient with myasthenia gravis, and in a human T cell line. It was not made in normal thymocytes or thymocytes treated with thymosin. Hormones had no effect on the synthesis of cytoplasmic glycoproteins.