Protein kinase C activity in activated human T-lymphocytes stimulated by interleukin-2

Interleukin-2 and phorbol 12-myristate 13-acetate (PMA) are shown to induce DNA-synthesis in human T-lymphocytes activated with phytohaemagglutinin. However, whereas PMA induced a rapid and persistent translocation of protein kinase C from cytosol to particulate fraction, no translocation was observed upon stimulation with interleukin-2. Treatment with PMA for 72 h caused a slow down-regulation of protein kinase C activity to less than 10% of unstimulated T-lymphocytes and was mainly located in the particulate fraction. In contrast, stimulation with phytohaemagglutinin increased the total cellular protein kinase C activity by approx. 100% but with an unaltered subcellular distribution. However, interleukin-2-induced DNA synthesis in PMA- and phytohaemagglutinin-stimulated T-lymphocytes was comparable. Further, maximal DNA synthesis was shown to be dependent on the continuous presence of interleukin-2. These results indicate that interleukin-2-induced proliferation of activated human T-lymphocytes can occur without a translocation of protein kinase C from the cytosol to the particulate fraction and that interleukin-2 most likely functions as a progression factor.