Description | Inositol phosphates are a family of water-soluble intracellular signaling molecules derived from membrane inositol phospholipids. They undergo a variety of complex interconversion pathways, and their levels are dynamically regulated within the cytosol in response to a variety of agonists. D-Myo-inositol (3,4,5,6) tetrakisphosphate (Ins(3,4,5,6)P4) has a direct biphasic (activation/inhibition) effect on an epithelial Ca2+-activated chloride channel. The effect of Ins(3,4,5,6)P4 is not mimicked by other inositol tetrakisphosphate isomers, is dependent on the prevailing calcium concentration, and is influenced when channels are phosphorylated by calmodulin kinase II. The predominant effect of Ins(3,4,5,6)P4 on phosphorylated channels is inhibitory at levels of intracellular calcium observed in stimulated cells. Ins(3,4,5,6)P4 activity acts to inhibit calcium-dependent chloride secretion. The secretion of fluid and electrolytes across intestinal epithelial cells in response to Ca2+-dependent secretagogues is a tightly regulated process that is subject to both positive and negative influences. Agonists of Gq protein-coupled receptor (GqPCRs) appear to have the ability to evoke antisecretory mechanisms. One is mediated by the generation of Ins(3,4,5,6)P4 and serves to chronically downregulate epithelial responsiveness to subsequent challenge with Ca2+-dependent agonists. (PMID: 12388102, 11408264) |
Chemical_IUPAC_Name | [(1R,2S,3S,4R,5S,6R)-3,4-dihydroxy-2,5,6-triphosphonooxycyclohexyl] dihydrogen phosphate |