Abstract
The family of phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks) is emerging from a comparative backwater in inositide signalling into the mainstream, as is their substrate, phosphatidylinositol 5-phosphate (PI5P). Here we review some of the key questions about the PI5P4Ks, their localisation, interaction, and regulation and also we summarise our current understanding of how PI5P is synthesised and what its cellular functions might be. Finally, some of the evidence for the involvement of PI5P4Ks in pathology is discussed.
Highlights
The phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks, EC 2.7.1.149) are a family of three in most vertebrates e see (Clarke and Irvine, 2012, 2013)
It is generally accepted that the reaction they catalyse in vivo is the 4-phosphorylation of PI5P, and because of the much lower abundance of this lipid compared to PI4P (the major precursor of PI(4,5)P2 and substrate of the phosphatidylinositol 4phosphate 5-kinases, PI4P5Ks), it is accepted that their most likely function is to remove PI5P and control its levels in the cell
If the pool of PI(4,5)P2 synthesised by the PI5P4K route does have a function, it must be a specific and localised one, given that the amount will be much lower than the overall cellular levels of PI(4,5)P2
Summary
The phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks, EC 2.7.1.149) are a family of three in most vertebrates e see (Clarke and Irvine, 2012, 2013). These results provide evidence that in these cells most of the cellular pool of PI5P is dependent upon PIKfyve, but the remaining 15% is presumably synthesized via a PIKfyve-independent route.
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