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Direct Supervisor: Marco E. Bianchi, PhD
Location: Unit of chromatin remodeling, Department of Functional Genomics
Descriptive title of research activity: Role of HMGB-1 as a chemokine in tissue inflammation and repair.
Overall goals: we are interested in defining the roles of HMGB1 as a necrosis signal and cytokine promoting cell migration in areas of tissue injury and repair.
Rationale and significance: HMGB1 is a nuclear protein involved in the control of chromatin accessibility. When cells die by necrosis, HMGB1 is released in the extracellular medium. Cell dying by apoptosis do not release HMGB1, even after undergoing secondary necrosis, because they bind HMGB1 irreversibly to nucleosomes. Thus, HMGB1 is a signal of cell necrosis and tissue damage. As such, it induces different responses in different cells: inflammatory cells are activated, endothelial and smooth muscle cells divide, and several cell types migrate. In all these cases, the Receptor for Advanced Glycation End products (RAGE) is involved. HMGB1 is a strong chemotactic signal for monocytes. Other cells, such as fibroblasts, smooth muscle cells, endothelial cells and neutrophils and are also sensitive to HMGB1.
Description of work and methodology: we have previously shown that purified RAGE (whether made in bacteria or in mammalian cells) does not bind HMGB1. However, a dominant-negative RAGE receptor blocks chemotaxis induced by HMGB1. We have deduced that RAGE must have a coreceptor and will pursue the identification of such coreceptor. To this aim we will use several complementary approaches. The first is a classical approach: we will use all specific signal transduction inhibitors known, to see which inhibit HMGB1-induced chemotaxis. Moreover, we will transduce 3T3 cells with dominant negatives, again to identify players involved in HMGB1-induced chemotaxis. The second is a proteomic approach: 2D gels of 3T3 cells prior and following HMGB1 exposure will be compared, differential spots will be excised and proteins identified by MALDI/TOF.
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