description
: INOSITOL-1-4-5-TRISPHOSPHATE is a secondary messenger molecule used in signal transduction and lipid signaling. It mediates the biological response of a large number of hormones and neurotransmitters in target cells by regulating calcium release from intracellular stores. : INOSITOL-1-4-5-TRISPHOSPHATE is synthesized by hydrolysis of : PHOSPHATIDYL-MYO-INOSITOL-45-BISPHOSPHA "phosphatidylinositol 4,5-bisphosphate" (PIP2), a phospholipid that is located in the plasma membrane, by the action of phospholipase C, as described in : PWY-6351. Once formed, the levels of : INOSITOL-1-4-5-TRISPHOSPHATE are tightly regulated by two mechanisms. In the first mechanism the compound is dephosphorylated to : INOSITOL-1-4-BISPHOSPHATE , initiating a pathway that recycles the inositol moiety to the plasma membrane as phosphatidylinositols (see : PWY-6363). In the second mechanism, which is described here, : INOSITOL-1-4-5-TRISPHOSPHATE is phosphorylated by inositol 1,4,5-trisphosphate 3-kinase to : CPD-506. This compound has been suggested to have roles in controlling calcium homeostasis, transferring calcium between intracellular stores, and/or regulating calcium entry across the plasma membrane . It may also play a role in regulating cross-talk between the calcium and other signaling pathways. A : CPD-506-binding protein has been identified that can stimulate the GTPase activity of the ras and rap small GTP binding proteins . : CPD-506 is cleaved to : INOSITOL-1-3-4-TRIPHOSPHATE , and synthesis of : MI-HEXAKISPHOSPHATE proceeds from there, as described in : PWY-6362. : INOSITOL-1-3-4-TRIPHOSPHATE also acts as a link between the degree and duration of receptor-dependent phospholipase C activation (expressed as levels of : INOSITOL-1-4-5-TRISPHOSPHATE and thus : INOSITOL-1-3-4-TRIPHOSPHATE) and the generation of other second messenger compounds such as : INOSITOL-1456-TETRAKISPHOSPHATE and : CPD-178 (see : PWY-6366 and : PWY-6365)

external resources
NCBI:545328
BIOCYC:HUMAN_PWY-6364
PUBMED:3010126
PUBMED:1659392
PUBMED:6285891
PUBMED:6095097
PUBMED:7637787
PUBMED:9038348

genes
INPP5A , INPP5B , INPP5D , INPPL1 , ITPKA , ITPKB , OCRL , PTEN , SYNJ1 , SYNJ2 , MINPP1 , INPP5J , INPP5K , ITPKC , IPMK ,