Novel role of sphingosine kinase 1 as a mediator of neurotrophin-3 action in oligodendrocyte progenitors.
We had found previously that neurotrophin-3 (NT-3) is a potent stimulator of cAMP-response element binding protein (CREB) phosphorylation in cultured oligodendrocyte progenitors. Here, we show that CREB phosphorylation in these cells is also highly stimulated by sphingosine-1-phosphate (S1P), a sphingolipid metabolite that is known to be a potent mediator of numerous biological processes. Moreover, CREB phosphorylation in response to NT-3 involves sphingosine kinase 1 (SphK1), the enzyme that synthesizes S1P. Immunocytochemistry and confocal microscopy indicated that NT-3 induces translocation of SphK1 from the cytoplasm to the plasma membrane of oligodendrocytes, a process accompanied by increased SphK1 activity in the membrane fraction where its substrate sphingosine resides. To examine the involvement of SphK1 in NT-3 function, SphK1 expression was down-regulated by treatment with SphK1 sequence-specific small interfering RNA. Remarkably, the capacity of NT-3 to protect oligodendrocyte progenitors from apoptotic cell death induced by growth factor deprivation was abolished by down-regulating the expression of SphK1, as assessed by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Altogether, these results suggest that SphK1 plays a crucial role in the stimulation of oligodendrocyte progenitor survival by NT-3, and demonstrate a functional link between NT-3 and S1P signaling, adding to the complexity of mechanisms that modulate neurotrophin function and oligodendrocyte development.
Saini
Harsimran S
HS
Department of Biochemistry, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0614, USA.
Coelho
Rochelle P
RP
Goparaju
Sravan K
SK
Jolly
Puneet S
PS
Maceyka
Michael
M
Spiegel
Sarah
S
Sato-Bigbee
Carmen
C
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western / Q000379:methods; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects; D020287:In Situ Nick-End Labeling / Q000379:methods; D008246:Lysophospholipids / Q000494:pharmacology; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D020933:Neurotrophin 3 / Q000494:pharmacology*; D009836:Oligodendroglia; D010766:Phosphorylation / Q000187:drug effects; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011493:Protein Kinase C / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013234:Stem Cells / Q000187:drug effects* / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology; D045162:Thiazolidinediones; D013871:Thiones / Q000494:pharmacology; D013997:Time Factors; D000099157:Sphingosine Kinase
D017362:Cyclic AMP Response Element-Binding Protein; D008246:Lysophospholipids; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020933:Neurotrophin 3; D017853:Phosphotransferases (Alcohol Group Acceptor); D011493:Protein Kinase C; D034741:RNA, Small Interfering; D013110:Sphingosine; D013844:Thiazoles; D045162:Thiazolidinediones; D013871:Thiones; D000099157:Sphingosine Kinase; C500091:thiazolidine-2,4-thione; C060504:dihydrosphingosine 1-phosphate; C060506:sphingosine 1-phosphate; C061800:N,N-dimethylsphingosine