Lipid signaling



  Lipid signaling, broadly defined, refers to any biological signaling event involving a monoamine neurotransmitters) because lipids can freely diffuse through membranes. One consequence of this is that lipid messengers cannot be stored in vesicles prior to release and so are often biosynthesized "on demand" at their intended site of action. As such, many lipid signaling molecules cannot circulate freely in solution but, rather, exist bound to special carrier proteins in serum.

Activators of G-protein coupled receptors

See main article on G-protein coupled receptors

Lysophosphatidic acid (LPA)

LPA is the result of phospholipase A2 action on G-protein coupled receptors LPA1, LPA2, and LPA3 (also known as EDG2, EDG4, and EDG7, respectively).

Sphingosine-1-phosphate (S1P)

S1P is present at high concentrations in plasma and secreted locally at elevated concentrations at sites of inflammation. It is formed by the regulated G-protein coupled receptors, S1P1 - S1P5. Interestingly, targeted deletion of S1P1 results in lethality in mice and deletion of S1P2 results in seizures and deafness. Additionally, a mere 3- to 5-fold elevation in serum S1P concentrations induces sudden cardiac death by an S1P3-receptor specific mechanism.

Platelet activating factor (PAF)

PAF is a potent activator of platelet aggregation, inflammation, and anaphylaxis. It is similar to the ubiquitous membrane G-protein coupled receptor, PAFR and is inactivated by PAF acetylhydrolase.

The Endocannabinoids

The endogenous anandamide in most tissues.

Elevations in either of these lipids causes analgesia and anti-inflammation but the precise roles played by these two endocannabinoids are still vague and intensive research into their function, metabolism, and regulation is ongoing.

Prostaglandins

Main article: Eicosanoids

nuclear receptors, see below).

Retinoic acid derivatives

Main article: visual cycle

rhodopsin which ulitmately leads to depolarization of the neuron thereby enabling visual perception.

Activators of nuclear receptors

See the main article on nuclear receptors

Steroid Hormones

This large and diverse class of progestagens.

Retinoic acid Derivatives

A number of nuclear receptors such as the RAR and RXR to mediate differentiation and proliferation of many types of cells.

Prostaglandins

Main article: Eicosanoids

The majority of PPAR family. (See article eicosanoid receptors for more information).

Second messengers

Main article: second messenger system

Diacylglycerol

Main article: diglyceride

The key event of enzyme. All six known families of PLC catalyze this reaction. IP3 is soluble and diffuses freely into the cytoplasm. It is recognised by the inositol triphosphate receptor(IP3R), a Ca2+ channel in the endoplasmic reticulum(ER) membrane. The ER acts as intracellular Ca2+ store. The binding of IP3 to IP3R releases the flow of calcium from the ER into the normally Ca2+-poor cytoplasm, which then triggers various events of Protein kinase C family. Thus, both IP3 and DAG contribute to activation of PKCs.[1][2]

Protein kinase C-α is a conventional PKC and requires both DAG and Ca2+ for activity. One of the targets activated by PKC-α is phospholipase D, which hydrolyses phosphatidylcholine(PC) to fatty acid composition. PC forms the bulk of the lipids of the plasma membrane and provides an inexhaustible supply of substrates for PLD. DAG produced through this mechanism may continue to activate PKC hours after the initial extracellular stimulus.

See also

References

  1. ^ Irvine RF (1992). "Inositol lipids in cell signalling". Curr. Opin. Cell Biol. 4 (2): 212–9. PMID 1318060.
  2. ^ Nishizuka Y (1995). "Protein kinase C and lipid signaling for sustained cellular responses" (pdf). FASEB J. 9 (7): 484–96. PMID 7737456.
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TFIID, TFIIH) - Adaptor protein
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DAG - IP3 - IP3 receptor
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Lipid_signaling". A list of authors is available in Wikipedia.