Fig. 5.

Model describing a role for IPMK in both activation and inhibition of Akt. In response to extracellular stimuli such as growth factors, the p110/p85 PI3Ks produce PIP₃ in the plasma membrane, which results in the activation of a host of kinases, including Akt. One such kinase phosphorylates IPMK, activating its PI3K activity and resulting in a feed-forward loop necessary for maximal PIP₃ levels and Akt activity. A distinct kinase, perhaps in response to some other specific signal, phosphorylates IPMK on a different site, thus activating its inositol phosphate kinase activity. Inositol phosphates including IP₄, IP₅, and IP₇ have been reported to antagonize Akt signaling.