Studying polyphosphorylation, a novel PTM, in mammalian cell lines

Abstract

Polyphosphates are long chains of phosphates attached to one another via high‐energy phosphoanhydride bonds. The literature reports their implication in a variety of medically related functions, such as apoptosis, blood coagulation, and inflammation. The mechanisms involved with polyphosphate and its functions have been studied in bacteria and in yeast, but the synthesis pathway of polyphosphate in mammals is still unknown. Moreover, the concentrations of polyphosphate in mammalian cells (<1mM) are much lower than the ones found in yeast (100–200mM). This makes it challenging to study polyphosphate biology and polyphosphorylation in mammalian cell lines. Recently, Azevedo, et al. (2015) identified a new PTM in yeast called polyphosphorylation and two targets of this PTM: Nsr1 and Top1. It consists of the non‐enzymatic covalent attachment of polyphosphate chains to lysine residues found in a poly‐acidic serine and lysine‐rich (PASK) motif. Our lab has since identified 24 novel yeast targets being polyphosphorylated. Our next aim was to test if human proteins can also be polyphosphorylated. In order to modulate the concentrations of polyphosphate in the cell, we transfected mammalian cells with PPK1, an E. coli enzyme that synthesizes polyphosphate. This ectopic expression allowed us to perform a small “screen” and identify 6 human proteins that can be polyphosphorylated: nucleolin, hNop56, Mesd chaperone, DEK, eIF5B and UPF3B. We will present our latest work focused on determining the molecular function of polyphosphorylation in mammalian cells.Support or Funding InformationThis project is funded by the Canadian Institutes of Health Research (CIHR).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.