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style="background: #F8EABA; text-align: center;" colspan="2"	Inositol triphosphate
Image:IP3.png
Identifiers
Properties
Hazards
style="background: #F8EABA; text-align: center;" colspan="2"	Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Inositol trisphosphate or inositol 1,4,5-trisphosphate (also commonly known as triphosphoinositol; abbreviated InsP₃ or IP₃), together with diacylglycerol, is a second messenger molecule used in signal transduction in biological cells. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂), a phospholipid that is located in the plasma membrane, by phospholipase C.

Its main functions are to mobilize Ca²⁺ from storage organelles and to regulate cell proliferation and other cellular reactions. For example, in the fruit fly Drosophila, InsP₃ is used for intracellular transduction of light recognition in eye cells.

In smooth muscle cells, IP₃ binds to and activates the InsP₃ receptor on the membrane of the sarcoplasmic reticulum (SR) opens a calcium channel, resulting in the release of Ca²⁺ into the sarcoplasm^[1]. This increase in Ca²⁺ activates the ryanodine receptor-operated channel on the SR, leading to a further increase in the Ca²⁺ concentration in the muscle cell, resulting in the contraction of the muscle cell^[2].

Inositol tetra-, penta-, and hexa-phosphates have been implicated in gene expression by Shen^[3] and Steger^[4] (both in Science Magazine).

[edit] See also

• inositol
• inositol phosphate
• myo-inositol.
• inositol pentakisphosphate
• inositol hexaphosphate
• inositol triphosphate receptor

[edit] External links

• MeSH Inositol+1,4,5-Trisphosphate

[edit] References

1. ↑ Ferris CD, Snyder SH. IP3 receptors. Ligand-activated calcium channels in multiple forms. Adv Second Messenger Phosphoprotein Res. 1992;26:95-107. PMID 1329896
2. ↑ Somlyo AP, Somlyo AV. Signal transduction and regulation in smooth muscle. Nature. 1994 Nov 17;372(6503):231-6. PMID 7969467
3. ↑ Shen X, et al. Modulation of ATP-dependent chromatin-remodeling complexes by inositol polyphosphates. Science. 2003 Jan 3;299(5603):112-4. PMID 12434013
4. ↑ Steger DJ, et al. Regulation of chromatin remodeling by inositol polyphosphates. Science. 2003 Jan 3;299(5603):114-6. PMID 12434012

v·d·e Cell signaling: lipid signaling
Phospholipase - PIP2 - DAG - IP3 - IP3 receptor

v·d·e Cell signaling: calcium signaling
Second messengers	IP3 - NAADP - cADPR
Intracellular calcium store gates	IP3 receptor - Ryanodine receptor - putative NAADP receptor
Calcium pumps and exchangers	SERCA - Na/Ca antiport - Ca/H antiport
calcium binding protein domains	colspan="1" style="text-align:left;width:100%;font-size:95%;background:#f7f7f7;" Template:! EF hand domain - C2 domain[[#if:Troponin C - CaM - CaM kinases - PKC - NCS]][[#if:Calbindin - S100 - pervalbumin - Calretinin - Calsequestrin - Sarcalumenin - Phospholamban - Synaptotagmins]][[#if:Calpain]][[#if:Gelsolin]][[#if:VDCC - TRP - NMDA receptor - AMPA receptor - 5-HT3 receptor - P2X Receptor]][[#if:calreticulin - calnexin]][[#if:Cadherin]][[#if:Parathyroid hormone - Calcitonin - calcium receptor - vitamin D]]

Catebory:Muscle

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pl:Trifosforan inozytolu

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