The results of a large number of studies indicate that interleukin 1 (IL 1), a protein produced and secreted by activated monocytes, macrophages, and neutrophils stimulates the maturation, functional activation, and proliferation of a broad spectrum of cell types that share a common involvement in immune or inflammatory responses. In view of the proposed role of IL 1 in immunity and inflammation, we have focused our studies on the characterization of the factors that control the synthesis, secretion, and extracellular processing of IL 1 in murine and human monocytes and macrophages as well as human neutrophils. We have demonstrated that IL 1alpha and beta are secreted via a novel pathway that is markedly stimulated by calcium ionophores. In addition, we have found that the IL 1alpha precursor is a substrate for the calcium-dependent protease, calpain. In this application we have proposed a series of experiments that are designed to elucidate the sequence of events that result in IL 1alpha and beta secretion from monocytes and macrophages. We are particularly interested in the role of calcium in IL 1 secretion since we have found that elevations in intracellular calcium are associated with heightened IL 1alpha and beta secretion and processing. It is our intent to define the mechanism(s) by which calcium enhances IL 1 secretion. Furthermore, we plan to characterize the signal sequences or domains in the IL 1alpha and beta proteins that are required for secretion. These experiments will involve the transfection of expression plasmids containing truncated forms of the IL 1alpha and beta precursor into cell line macrophages followed by the measurement of the secretion of these altered IL 1 proteins. Finally, we plan to characterize the possible role of protein unfolding in the secretory process and use subcellular fractionation and immunomicroscopy to define the site(s) of IL 1 secretion in macrophages.
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