Cell Extraction and Enrichment of Inositol Polyphosphate and Inositol Pyrophosphates Using Titanium Dioxide

Inositol polyphosphates are ubiquitously present in eukaryotic cells and play important roles in diverse cellular processes such as protein folding, signal transduction, and phosphate homeostasis. Although these negatively charged small metabolites are easily stripped from metals/proteins and extracted under strong acidic conditions, their low intracellular concentrations in some biological settings command a further enrichment step to facilitate downstream analyses. Here, we describe the use of titanium dioxide beads to enrich for inositol polyphosphate extracted from cultured mammalian cells. This protocol not only concentrates the diluted inositol phosphates but also removes salts and proteins that would otherwise interfere with postpurification analyses.