fosfoinositol

Fosfoinositol refers to a family of phosphorylated derivatives of the sugar alcohol inositol, including free inositol phosphates and the phosphorylated phosphatidylinositol lipids that reside in cellular membranes. These molecules play crucial roles in cell signaling, membrane trafficking, and cytoskeletal regulation. Inositol can be phosphorylated at multiple positions to form various inositol phosphates (for example IP3, IP4, IP5, IP6) and can also serve as the headgroup of glycerophospholipids to form phosphatidylinositols (PI) and their phosphorylated derivatives (PI4P, PI(4,5)P2, PI(3,4,5)P3).

Phosphatidylinositols are located primarily in the cytosolic leaflet of cellular membranes. Enzymes such as PI synthases and phosphoinositide kinases (PI4K, PI5K, PI3K) add phosphate groups to generate phosphoinositides that help define membrane identity and recruit signaling proteins. Phospholipase C acts on PI(4,5)P2 to produce diacylglycerol (DAG) and inositol trisphosphate (IP3), linking lipid signaling to calcium release and downstream responses. Free inositol phosphates, including IP3 and others, participate directly in signaling cascades that regulate processes such as calcium mobilization, enzyme activity, and gene expression.

In biological systems, fosfoinositol compounds are essential across eukaryotes, including animals, plants, and fungi. Dysregulation of phosphoinositide signaling is associated with diseases such as cancer, metabolic disorders, and neurodegeneration. The pathway is a focal point of pharmacological research, with inhibitors targeting PI kinases and phosphatases being investigated for therapeutic applications.