Tails wagging the dogs: On phosphoinositides and their fatty acyl moieties

Phosphoinositides (PIs) control various cellular functions of eukaryotic cells. PIs are derived from phosphatidylinositol (PtdIns) by phosphorylation of the inositol-ring in the lipid-head group; the action of specific lipid kinases gives rise to a family of structurally-related PIs, in plants representing PtdIns-mono-, and -bisphosphates. Specific PIs, such as phosphatidylinositol4,5-bisphosphate (PtdIns(4,5)P(2)), can influence more than one physiological process, raising the question as to how interactions with alternative protein partners are coordinated. Previous studies have proposed that PIs are organized by spatiotemporal compartmentation into distinct functional pools, however, mechanisms for the generation and maintenance of such pools have not been presented. Several recent studies now indicate that not only the distinctive inositolpolyphosphate head groups may be relevant for PI function but also the associated fatty acyl-moieties, which may be involved in sorting of PI precursors into distinct pools. This mini-review aims at highlighting recent evidence that PI acylgroups exert relevant effects on signaling.