Identification of new FGF1 binding partners-Implications for its intracellular function

Besides its classical mode of action through activation of specific receptors at the cell surface, fibroblast growth factor 1 (FGF1) can also cross the cellular membrane and translocate into the cytosol and further to the nucleus. The mechanism of this translocation is described partially, but the role of FGF1 inside the cell remains unknown. The aim of our work was to identify novel binding partners of FGF1 to predict its intracellular functions. We combined three methods of identification of such partners based on different principles: yeast two-hybrid screen and mass spectrometry (MS) analysis of complexes obtained by Tandem Affinity Purification (TAP) or by co-precipitation from cell lysate using recombinant FGF1. Altogether, we identified twenty novel intracellular proteins interacting with FGF1. For selected proteins, their direct interaction with FGF1 was confirmed by pull-down assays and SPR measurements. Interestingly, half of the proteins found are involved in processes related to cell viability, such as apoptosis, cell proliferation, and cell cycle regulation. Thus, our study indicates that the role of intracellular FGF1 is to protect the cell against stress conditions by providing an additional signal for cell survival, independently of receptor-activated signaling cascades.