Probing the Function of PolyP on Signalling Networks in Mammalian Systems

Abstract

Polyphosphates (PolyP) are linear chains of inorganic phosphates joined together by phosphoanhydride bonds. This polyanionic molecule has been found in all organisms and has been implicated in diverse biological processes such as cell growth and blood coagulation. Nonetheless, the mechanism of polyP’s involvement in these processes and its impact at a molecular level is still unknown. In 2015, the addition of polyP chains to lysine residues was found to be a novel post-translational modification. However, a hurdle in studying the impact of polyP in the mammalian system is its low endogenous levels. In this study, I applied an ectopic expression system using E. coli-derived polyphosphate kinase 1 (PPK) in HEK293T cells to induce excess production of polyP. In mammalian cells, increased intracellular polyP levels lead to increased activation of both Erk1/2 and p70s6k. I also expanded our system by utilizing the yeast exopolyphosphatase, Ppx1, to deplete polyP. Overall, this work presents a novel role for polyP in mediating key signalling pathways and will help probe the function of polyP in mammalian cells.