Distribution of sphingosine kinase activity and mRNA in rodent brain

Abstract

Sphingosine-1-phosphate (S1P) is a lipid mediator that exerts multiple cellular functions through activation of a subfamily of G-protein-coupled receptors. Although there is evidence that S1P plays a role in the developing and adult CNS, little is known about the ability of brain parenchyma to synthesize this lipid. We have therefore analyzed the brain distribution of the enzymatic activity of the S1P synthesizing enzyme, sphingosine kinase (SPHK) [EC:2.7.1.91], as well as mRNA distribution for one of the two isoforms of this enzyme, sphingosine kinase 2. SPHK activity, measured by the conversion of [ 3 H]sphingosine to [ 3 H]S1P, is highest in cerebellum, followed by cortex and brainstem. Lowest activities were found in striatum and hippocampus. Sensitivity to 0.1% Triton-X suggests that this activity is accounted for by SPHK2. RT-PCR and in situ hybridization studies show that mRNA for this isoform has a distribution similar to that of SPHK activity. In vivo and in vitro ischemia increase SPHK activity and SPHK2 mRNA levels. These results indicate that SPHK2 is the predominant S1P-synthesizing isoform in normal brain parenchyma. Sphingosine-1-phosphate (S1P) exerts a wide variety of biological activities in many vertebrate cell types. It was initially proposed to act as a second messenger, based on the ability of extracellular growth factors to activate sphingosine kinase (SPHK) [EC:2.7.1.91] and increase intracellular S1P levels. However, the putative site that mediates these intracellular actions of S1P has not been identified. The discovery and cloning of five S1P receptors (S1P 1 /EDG 1 , S1P 2 /EDG 5 , S1P 3 /EDG 3 , S1P 4 /EDG 6 , and S1P 5 /EDG 8 ) has stimulated the notion that S1P acts as an extracellular signaling molecule, regulating a host of cellular functions such as proliferation, immunomodulation, apoptosis, migration, cytoskeletal organization, and differentiation/morphogenesis (Hla 2003 The present address of Kamil Topalkara is the Department of Neurology, Faculty of Medicine, Cumhuriyet University, Sivas, 58140 Turkey. 3 The present address of Margherita Popolo is the Service de Neurologie, Hôpital Pasteur, BP69, Av de la voie Romaine, 06002 Nice Cedex 1, France.Abbreviations used: BSA, bovine serum albumin; MCA, middle cerebral artery; OGD, oxygen glucose deprivation; PBS, phosphatebuffered saline; S1P, sphingosine-1-phosphate; SDS, sodium dodecyl sulphate; SPHK, sphingosine kinase.Journal of Neurochemistry, 2007Neurochemistry, , 103, 509-517 doi:10.1111Neurochemistry, /j.1471Neurochemistry, -4159.2007 Kleuser et al. 1998;Shu et al. 2002). Activated platelets represent a major source of S1P (English et al. 2000(English et al. , 2001Yatomi et al. 2000). S1P levels in serum are considerably higher than in plasma (0.4 vs. 0.1 lmol/L, respectively). However, the interaction of S1P with low-density lipoprotein (Kimura et al. 2001) might reduce the free concentration of S1P, possibly as a protection mechanism from full activation of vascular S1P receptors.The fact that the brain is ...

Antagonism of Sphingosine 1-Phosphate Receptor-2 Enhances Migration of Neural Progenitor Cells Toward an Area of Brain Infarction

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The roles of bile acids and sphingosine-1-phosphate signaling in the hepatobiliary diseases

“…Unlike SphK1, high expression of SphK2 was observed mainly in adult kidney, liver, and brain, compared with other tissues (39,40). Recently, it was demonstrated that conjugated bile acids signal through the S1PR2 and activate SphK2 (11).…”

Cellular Localization of Sphingosine-1-phosphate Receptor 1 Expression in the Human Central Nervous System

“…FTY720 is a structural analogue of sphingosine and has biological activity in vivo by being phosphorylated by SPHKs (Mandala et al 2002), which are abundantly expressed in the brain (Blondeau et al 2007;Bryan et al 2008). The phosphorylated form of FTY720 (FTY720P) activates S1PRs, mainly S1PR1, in a fashion similar to that of endogenous S1P.…”