Sphingosine kinase (SphK) is a conserved

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

kinase In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule don ...

that catalyzes formation sphingosine-1-phosphate (S1P) from the precursor

sphingolipid Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sp ...

sphingosine Sphingosine (2-amino-4-trans-octadecene-1,3-diol) is an 18-carbon amino alcohol with an unsaturated hydrocarbon chain, which forms a primary part of sphingolipids, a class of cell membrane lipids that include sphingomyelin, an important phosphol ...

. Sphingolipid metabolites, such as

ceramide Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of Eukaryote, eukaryotic cells, since they are co ...

and sphingosine-1-phosphate, are lipid second messengers involved in diverse cellular processes. There are two forms of SphK, SphK1 and SphK2. SphK1 is found in the

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...

of eukaryotic cells, and migrates to the

plasma membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

upon activation. SphK2 is localized to the nucleus.

Function

S1P has been shown to regulate diverse cellular processes. It has been characterized as a

lipid signaling Lipid signaling, broadly defined, refers to any biological cell signaling event involving a lipid messenger that binds a protein target, such as a receptor (biochemistry), receptor, kinase or phosphatase, which in turn mediate the effects of these ...

molecule with dual function. On one hand, it exerts its actions extracellularly by binding to the five different S1P

receptors Receptor may refer to: *Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds ...

that couple to a variety of G-proteins to regulate diverse biological functions, ranging from cell growth and survival to effector functions, such as proinflammatory mediator synthesis. On the other hand, it appears to act as an intracellular

second messenger Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form of cell signaling, encompassing both first m ...

, although the relevant molecular target(s) to which it binds within cells remains to be discovered. The role of S1P in various functions of cells and tissues is established, including regulation of cell survival and motility, angiogenesis, and inflammatory responses. Sphingosine kinases (SphKs) types 1 and 2, the two enzymes identified so far in mammals that produce S1P by ATP-dependent

phosphorylation In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writ ...

, have therefore received considerable interest.

Sphingolipid metabolism

Sphingolipid Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sp ...

s are ubiquitous membrane constituents of all eukaryotic cells. In general, the term sphingolipid (SL) refers to any of a number of lipids consisting of a head group attached to the 1-OH of

(Cer).

Ceramide Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of Eukaryote, eukaryotic cells, since they are co ...

s consist of a sphingoid base, commonly referred to as a long-chain base (LCB), which is N-acylated. De novo synthesis of LCBs begins with the condensation of

palmitoyl-CoA Palmitoyl-CoA is an acyl-CoA thioester. It is an "activated" form of palmitic acid and can be transported into the mitochondrial matrix by the carnitine shuttle system (which transports fatty acyl-CoA molecules into the mitochondria), and once in ...

with

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...

, forming 3-ketosphinganine (Fig. 1). This product is then reduced to

sphinganine Safingol is a lyso-sphingolipid protein kinase inhibitor. It has the molecular formula C18H39NO2 and is a colorless solid. Medicinally, safingol has demonstrated promising anticancer potential as a modulator of multi-drug resistance and as an ind ...

, also known as dihydrosphingosine (dihydro-Sph; 2-amino-1,3-dihydroxy-octadecane). A 14– to 26-carbon

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

chain is then added in an

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

linkage with the 2-amino group, forming dihydroceramide (dihydro-Cer). A head group, such as

phosphocholine Phosphocholine is an intermediate in the synthesis of phosphatidylcholine in tissues. Phosphocholine is made in a reaction, catalyzed by choline kinase, that converts ATP and choline into phosphocholine and ADP. Phosphocholine is a molecule ...

or a

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

, can now be added to the 1-OH, forming a

, although most sphingolipids of higher eukaryotes contain further modifications of the LCB. Sphk1 diag b

Popular culture

During "100,000 Airplanes", a third season episode of ''

The West Wing ''The West Wing'' is an American political drama television series created by Aaron Sorkin that was originally broadcast on NBC from September 22, 1999, to May 14, 2006. The series is set primarily in the West Wing of the White House, where t ...

'', sphingosine kinase is fictitiously described as "the enzyme believed to control all signal pathways to cancer growth." Learning of it inspires the protagonist of the series, President Josiah Bartlet, to consider launching an Apollo program to cure cancer.

References

External links

* {{DEFAULTSORT:Sphingosine Kinase EC 2.7.1 Lipids

Function

Sphingolipid metabolism

Popular culture

References

Further reading

External links