Figure 3:

Representation of cellular functions of inositol pyrophosphates in an eukaryotic cell. 1 IP₇ physiologically inhibits AKT signalling by competitively binding to the PH domain of AKT and thus preventing it from binding to PI(3,4,5)P₃ (PIP3). IP₇ and IP6K2 promote, 2 apoptosis and 3 formation of autophagosomes. 4 PP-IPs regulate the cellular levels of ATP by their action on the glycolysis pathway and mitochondrial membrane potential. 5 IP₇ is responsible for maintaining endoplasmic reticulum morphology in yeast cells. 6 IP₇-mediated pyrophosphorylation regulates dynein binding to membranes and thereby influences Golgi morphology. 7 PP-IPs positively regulate the synthesis of polyphosphates in yeast vacuoles. 8 In pancreatic β cells, IP₇ upregulates insulin secretion by increasing the readily releasable pool of insulin granules docked at the plasma membrane. 9 IP₇ inhibits the synaptic exocytotic pathway in neurons. In the nucleus, PP-IPs are responsible for 10 telomere length maintenance in yeast, 11 DNA repair via the homologous recombination (HR) and nucleotide excision repair (NER) pathways, and 12 epigenetic modifications that influence chromatin remodelling to control global transcription. 13 In yeast, IP₇ influences ribosome biogenesis by regulating nucleolar rDNA transcription.