Cellular delivery and photochemical release of a caged inositol-pyrophosphate induces PH-domain translocation in cellulo

Inositol pyrophosphates, such as diphospho-myo-inositol pentakisphosphates (InsP₇), are an important family of signalling molecules, implicated in many cellular processes and therapeutic indications including insulin secretion, glucose homeostasis and weight gain. To understand their cellular functions, chemical tools such as photocaged analogues for their real-time modulation in cells are required. Here we describe a concise, modular synthesis of InsP₇ and caged InsP₇. The caged molecule is stable and releases InsP₇ only on irradiation. While photocaged InsP₇ does not enter cells, its cellular uptake is achieved using nanoparticles formed by association with a guanidinium-rich molecular transporter. This novel synthesis and unprecedented polyphosphate delivery strategy enable the first studies required to understand InsP₇ signalling in cells with controlled spatiotemporal resolution. It is shown herein that cytoplasmic photouncaging of InsP₇ leads to translocation of the PH-domain of Akt, an important signalling-node kinase involved in glucose homeostasis, from the membrane into the cytoplasm.