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The internalization and intracellular transport of IL-1 and its receptor were examined in the murine T cell line EL-4. For 4 h after internalization intracellular 125I-IL-1 alpha remains bound to its receptor without degradation. Electron microscope autoradiography demonstrates that internalized IL-1 accumulates in purified nuclei. The IL-1 extracted from these nuclei is still bound to receptor. As no receptors for IL-1 were detected in untreated nuclei, these results suggest IL-1 driven translocation of the cell surface IL-1R complex to the nucleus. IL-1R internalization was correlated with IL-1 signal transduction events required to induce growth factor production from several subclones of EL-4 cells. The subsequent transport of the internalized IL-1R complex to the nucleus suggests the possibility for a nuclear site for IL-1R signaling.
Curtis et al. (Thu,) studied this question.