Elucidating Diphosphoinositol Polyphosphate Function with Nonhydrolyzable Analogues

The diphosphoinositol polyphosphates (PP‐IPs) represent a novel class of high‐energy phosphate‐containing messengers which control a wide variety of cellular processes. It is thought that PP‐IPs exert their pleiotropic effects as allosteric regulators and through pyrophosphorylation of protein substrates. However, most details of PP‐IP signaling have remained elusive because of a paucity of suitable tools. We describe the synthesis of PP‐IP bisphosphonate analogues (PCP‐IPs), which are resistant to chemical and biochemical degradation. While the two regioisomers 1PCP‐IP5 and 5PCP‐IP5 inhibited Akt phosphorylation with similar potencies, 1PCP‐IP5 was much more effective at inhibiting its cognate phosphatase hDIPP1. Furthermore, the PCP analogues inhibit protein pyrophosphorylation because of their inability to transfer the β‐phosphoryl group, and thus enable the distinction between PP‐IP signaling mechanisms. As such, the PCP analogues will find widespread applications for the structural and biochemical characterization of PP‐IP signaling properties. Stable analogues of high‐energy messengers: Bisphosphonate analogues of the diphosphoinositol polyphosphate (PP‐IP) messengers are resistant to chemical and biochemical degradation. The compounds mimic the natural counterparts well when proteins are regulated allosterically by PP‐IPs, but have an opposing effect in protein pyrophosphorylation. Thus, the compounds can be used to elucidate PP‐IP signaling properties.