Inside and out, cells teem with signaling activity. And inositides – particularly inositol phosphates and inositol lipids – are everywhere, mediating everything from ion-channel function to vesicle trafficking, apoptosis, cell growth, motility, and differentiation.[1] Almost every cell uses one of the phosphoinositide signaling cascades: Receptors trigger the hydrolysis of the lipid phosphatidylinositol 4,5-bisphosphate to yield the second messengers, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol, which regulate intracellular calcium levels and protein kinase C, respectively.[2] But that's just the beginning for one example. "Inositide-dependent signaling is, at least indirectly, involved in all the cellular responses I can think of," says Alberto Martelli, University of Bologna.