REGULATION OF C-FOS EXPRESSION DURING T CELL ACTIVATION

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The immune function of T cells is dependent on their ability to proliferate in response to antigen, thus expanding specific T cell subsets. Stimulation of the T cell antigen receptor (TCR) with appropriately presented antigen induces synthesis of the interleukin 2 (IL2) receptor (IL2R), and of IL2. Stimulation of the IL2R with IL2 causes the T cells to proliferate. Our recent findings indicate that although early signaling through these two receptors differ, once a signal reaches the nucleus, early changes in gene expression seem to be the same. In particular, expression of the proto-oncogene c-fos is increased after activation of both receptor systems. The proto-oncogene c-fos is associated with many cell activation phenomena, and is the earliest gene whose synthesis is induced during activation of most cells. In the present proposal, we will explore the participation of the c-fos regulatory region in the activation of T cells. Specifically, we will delineate the binding activity of the c-fos promoter in response to several ligands and determine the area of DNA bound in response to each. We will investigate whether signaling pathways induced by the various stimuli converge before activating c-fos DNA binding proteins (DBP), or whether individual signaling pathways activate entirely different DBPs. We will also examine the possible existence or nonexistence of transcription-inhibiting binding proteins. We will determine if any differences exist in the DBP activated in fresh T cells compared with DBP activated or present in transformed T cell lines. We will determine the participation of increased (Ca2+)i, the Na/H antiport and the two protein kinases PKA and PKC in activation of c-fos specific DBP. Finally, we will isolate antibody against specific DBP and use this anitbody for study of intracellular location of the DBP in resting T cells, and how this location may change as a result of activation. We will determine the size, complexity, and potential activating or inactivating modifications of some of the c-fos DNA binding complexes.