| Inositol triphosphate | |
|---|---|
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| Identifiers | |
| CAS number | 85166-31-0 |
| PubChem | 55310 |
| Properties | |
| Molecular formula | C6H15O15P3 |
| Molar mass | 420.096 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP3 or IP3), together with diacylglycerol, is a secondary messenger molecule used in signal transduction and Lipid signaling in biological cells. While DAG stays inside the membrane, IP3 is soluble and diffuses through the cell. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, by phospholipase C.
Contents |
Mechanism
IP3 binds to and activates the InsP3 receptor on the membrane of the endoplasmic reticulum (ER), and sarcoplasmic reticulum (SR), opening a calcium channel, resulting in the release of Ca2+ into the cytoplasm, and sarcoplasm respectively.[1] This increase in Ca2+ activates the ryanodine receptor-operated channel on the SR, leading to a further increase in the Ca2+.
Function
Human
Its main functions are to mobilize Ca2+ from storage organelles and to regulate cell proliferation and other cellular reactions.
In smooth muscle cells, for example, the increase in concentration of cytoplasmic calcium results in the contraction of the muscle cell.[2]. For further reading of Ca2+-mediated functions, see functions of calcium in humans.
Fruit fly
For example, in the fruit fly Drosophila, InsP3 is used for intracellular transduction of light recognition in eye cells.
Sea urchin eggs
The slow block to polyspermy in the sea urchin is mediated by the phosphatidyl inositol diphosphate (PIP2) secondary messenger system. Activation of the binding receptors activates phospholipase C, which cleaves PIP2 in the egg plasma membrane, releasing inositol triphosphate (IP3) into the egg cell cytoplasm. IP3 diffuses to the endoplasmic reticulum, where it opens calcium channels.
See also
- inositol
- inositol phosphate
- myo-inositol
- inositol pentakisphosphate
- inositol hexaphosphate
- inositol triphosphate receptor
- ITPR1
- ITPKC
External links
References
- ^ Ferris CD, Snyder SH. IP3 receptors. Ligand-activated calcium channels in multiple forms. Adv Second Messenger Phosphoprotein Res. 1992;26:95-107. PMID 1329896
- ^ Somlyo AP, Somlyo AV. Signal transduction and regulation in smooth muscle. Nature. 1994 Nov 17;372(6503):231-6. PMID 7969467
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