Fig. 1: Overview of PI metabolism and the PI3K/AKT signaling pathway in cell dynamics.
From: Phosphoinositide signaling at the cytoskeleton in the regulation of cell dynamics
This diagram provides a comprehensive overview of PI metabolism within the cellular environment, highlighting the structure of the inositol ring with the 3rd, 4th, and 5th hydroxyl groups capable of phosphorylation. This process generates seven distinct PIPn isomers, whose interconversion is facilitated by PIPn kinases, phosphatases, and phospholipases—critical enzymes in this metabolic pathway. The diagram also highlights the PI3K/AKT signaling pathway, a key downstream effector of PIPn metabolism that regulates various cellular processes, particularly cell dynamics such as motility and adhesion. Notably, PtdIns(4,5)P2 4-phosphatase type I/II (PIP4P1/2), also known as TMEM55B/TMEM55A, has been proposed as PtdIns(4,5)P2 4-phosphatase [172]. However, the follow-up study found PIP4P1/TMEM55B to be catalytically inactive and lacking the typical catalytic CX5R motif [173]. To reflect this controversy, PIP4P1/2 is accompanied by a question mark, denoting the ongoing debate in the field. This diagram is generated using BioRender.
