B. Intracellular and extracellular signal transduction mediated by S100 proteins.
S100s are a unique group of EF-hand proteins characterized by cell-type and cell cycle- specific expression, as well as deregulated expression in neurological disorders (S100B- Alzheimer disease, Down syndrome, and epilepsy), inflammatory disorders (S100A8/A9- cystic fibrosis, arthritis and chronic bronchitis), and certain cancers (S100A2/A4/A6). At the cellular level, S100 proteins have been implicated in the control of cell growth and proliferation, cell cycle progression, and modulation of specific signal transduction pathways, but also have extracellular functions, including neurotrophic and antimicrobial activity. The structure of S100 proteins and their interactions with peptide fragments of target proteins have been extensively studied (e.g. Potts 1995, Maler 2002, Bhattacharya, 2003). However, almost no information is available on how these interactions effect signaling within a larger cellular context. Our research is aimed at a basic structural and biophysical understanding of how S100 proteins participate in signal transduction pathways in both intracellular and extracellular signaling systems, and is tightly coupled to functional studies in the laboratories of our collaborators. By determining the structural basis for the cellular activities of the S100 proteins, we seek to better define their roles in health and disease and evaluate the potential for S100 protein-based therapeutic strategies. This research is supported by NIH RO1 GM62112.
1. Intracellular- S100A6 modulation of SIP function. (Nowotny 2000, Lee 2004)
S100A6 has been shown to interact physically and functionally with Siah-1 interacting protein (SIP), which is an essential component of an E3 ligase complex that ubiquitinates β-catenin as part of the regulation of cell proliferation during embryogenesis. The connection to intracellular signaling via protein ubiquitination represents a fundamentally new area of investigation for S100 proteins. In addition to SIP, we are also working with a highly homologous target protein, Sgt1, which also binds S100A6 and is a member of both the core kinetochore and certain SCF E3 ubiquitin ligase complexes. The overall objective of our research is to understand downstream signaling mediated by S100 proteins. Thus, the objectives in this project are to determine the domain structures and organization of SIP and Sgt1, define the structural basis for their interaction with S100A6, and examine how S100 protein binding affects the structure and dynamics of these targets and their interactions with other known binding partners (e.g. Siah-1, Skp1, HSP90) from the relevant E3 complexes.
2. Extracellular-modulation of the function of RAGE by S100 proteins.
S100 proteins have been shown to interact with the cell surface Receptor for Advanced Glycation Endproducts (RAGE) that is implicated in diabetic atherosclerosis. S100 proteins are excreted in the cell types in which RAGE exerts its activity, and they are known to modulate RAGE function in a variety of biological processes including neurite outgrowth and immune cell response. The physical basis for S100 protein recognition of RAGE is currently not well characterized nor is RAGE's recognition of any of its ligands. The immediate goals in this project are to define the structural basis for the interaction of RAGE with S100 proteins, and determine the structural organization of the extracellular domains of RAGE as well as the changes induced by the binding and cross-talk between the S100 proteins and AGE ligands. We are also investigating approaches to the study of intact membrane-bound RAGE.
last updated April 26, 2004