Distribution of sphingosine kinase activity and mRNA in rodent brain.
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. Its heterogeneous distribution, in particular laminar distribution in cortex, suggests a neuronal localization and a possible role in cortical and cerebellar functions, in normal as well as ischemic brain.
Blondeau
Nicolas
N
Stroke and Neurovascular Regulation Laboratory, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Lai
Yushuan
Y
Tyndall
Sarah
S
Popolo
Margherita
M
Topalkara
Kamil
K
Pru
James K
JK
Zhang
Ling
L
Kim
Hyunghwan
H
Liao
James K
JK
Ding
Kan
K
Waeber
Christian
C
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D001923:Brain Chemistry / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D005947:Glucose / Q000172:deficiency; D002534:Hypoxia, Brain / Q000473:pathology; D017403:In Situ Hybridization; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology; D008246:Lysophospholipids / Q000378:metabolism; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000201:enzymology / Q000648:ultrastructure; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism; D000099157:Sphingosine Kinase
D005947:Glucose; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate