Pyrophosphoproteomics in HCT116 wildtype vs PPIP5K1/2 knockout

In vitro, both 5PP-InsP5 (IP7) and 1,5(PP)2InsP4 (IP8) can pyrophosphorylate peptides and proteins. It is unclear, which inositol pyrophosphate species is responsible for installing endogenous pyrophosphorylation in cells. In order to test this, we used HCT116 cells deficient in IP8 synthesis. Both enzymes that convert IP7 to IP8 are knocked out in this cell line. Importantly, this cell line does overaccumulates IP7, complicating the analysis.
We found no obvious difference in the number of observable pyrophosphorylation sites between the knockout and wildtype, suggesting that either IP7 or both molecules are responsible for creating pyrophosphoproteins in cells.