Møller, Henrik Devitt

The S100A4 protein has been found involved in the metastatic process of various aggressive cancer types. Tumors with highly up-regulated S100A4 is generally associated with bad prognosis and significant reduced survival chances. Several reports state that S100A4 promote cellular motility and invasion, probably through interactions with intracellular proteins, such as the non-muscle myosin heavy chain IIA (MHC-IIA), influencing the cytoskeleton dynamics (Alexandrova et al., 2000; Chen et al., 2001). Moreover, S100A4 has also extracellular functions, promoting breakdown of extracellular matrix components, supporting cell progression (Bjørnland et al., 1999; Semov et al., 2005). In this study, we wanted to develop a protein translocation system, using fluorescence biosensors of S100A4 and identified S100A4 targets in vitro, to monitor S100A4 interactions in vivo. Additionally, we would examine the existence of a possible common binding interface on different S100A4 intracellular targets including p53, MHC-IIA and liprin b1. We found that S100A4 had affinity for the blue fluorescence fusion protein (RevM10BL-BFP), used as biosensor for S100A4 target protein fragments, unfortunately creating to high signal background for practical use of this established protein translocation system. Nevertheless, we found evidence that supports the existence of small common S100A4 binding interface (the amino acid residues SLK S/N K/D), which is involved in S100A4 binding of p53 and MHC-IIA protein fragments in vitro.The S100A4 protein has been found involved in the metastatic process of various aggressive cancer types. Tumors with highly up-regulated S100A4 is generally associated with bad prognosis and significant reduced survival chances. Several reports state that S100A4 promote cellular motility and invasion, probably through interactions with intracellular proteins, such as the non-muscle myosin heavy chain IIA (MHC-IIA), influencing the cytoskeleton dynamics (Alexandrova et al., 2000; Chen et al., 2001). Moreover, S100A4 has also extracellular functions, promoting breakdown of extracellular matrix components, supporting cell progression (Bjørnland et al., 1999; Semov et al., 2005). In this study, we wanted to develop a protein translocation system, using fluorescence biosensors of S100A4 and identified S100A4 targets in vitro, to monitor S100A4 interactions in vivo. Additionally, we would examine the existence of a possible common binding interface on different S100A4 intracellular targets including p53, MHC-IIA and liprin b1. We found that S100A4 had affinity for the blue fluorescence fusion protein (RevM10BL-BFP), used as biosensor for S100A4 target protein fragments, unfortunately creating to high signal background for practical use of this established protein translocation system. Nevertheless, we found evidence that supports the existence of small common S100A4 binding interface (the amino acid residues SLK S/N K/D), which is involved in S100A4 binding of p53 and MHC-IIA protein fragments in vitro

Establishment of a translocation biosensor to monitor S100A4:target protein interactions in living cells

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Roskilde Universitet