Inositol triphosphate

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Inositol triphosphate
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 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 secondary 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.

Contents 1 Mechanism 2 Function 2.1 Human 2.2 Fruit fly 3 Sea urchin eggs 4 See also 5 External links 6 References

[edit] Mechanism

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⁺.

[edit] Function

[edit] 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 calcium concentration cell results in contraction of the muscle cell.^[2]. For further reading of Ca²⁺-mediated functions, see functions of calcium in humans.

[edit] Fruit fly

For example, in the fruit fly Drosophila, InsP₃ is used for intracellular transduction of light recognition in eye cells.

[edit] Sea urchin eggs

The slow block to polyspermy in the sea urchin is mediated by the phosphatidyl inositol diphosphate (PIP₂) secondery messenger system. Activation of the binding receptors activates phospholipase C, witch 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.

[edit] See also

• inositol
• inositol phosphate
• myo-inositol
• inositol pentakisphosphate
• inositol hexaphosphate
• inositol triphosphate receptor
• ITPR1
• ITPKC

[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

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 EF hand domain - C2 domain Calcium-based molecular switches, and kinases Troponin C - CaM - CaM kinases - PKC - NCS Intracellular calcium chelators (calcium buffers) and calcium sensors Calbindin - S100 - pervalbumin - Calretinin - Calsequestrin - Sarcalumenin - Phospholamban - Synaptotagmins Calcium-dependent proteases Calpain Calcium-dependent cytoskeleton remodeling proteins Gelsolin Cell membrane calcium channels VDCC - TRP - NMDA receptor - AMPA receptor - 5-HT3 receptor - P2X Receptor Calcium-regulated chaperones calreticulin - calnexin Calcium-based adhesion molecules Cadherin Calcium homeostasis Parathyroid hormone - Calcitonin - calcium receptor - vitamin D