Living organisms have evolved to contain a wide variety of receptors and si
gnaling pathways that are essential for their survival in a changing enviro
nment. Of these, the phosphoinositide pathway is one of the best conserved.
The ability of the phosphoinositides to permeate both hydrophobic and hydr
ophilic environments, and their diverse functions within cells have contrib
uted to their persistence in nature, In eukaryotes, phosphoinositides are e
ssential metabolites as well as labile messengers that regulate cellular ph
ysiology while traveling within and between cells. The stereospecificity of
the six hydroxyls on the inositol ring provides the basis for the function
al diversity of the phosphorylated isomers that, in turn, generate a select
ive means of intracellular and intercellular communication for coordinating
cell growth. Although such complexity presents a difficult challenge for b
ench scientists, it is ideal for the regulation of cellular functions in li
ving organisms.