Differential transactivation of sphingosine-1-phosphate receptors modulates NGF-induced neurite extension.
The process of neurite extension after activation of the TrkA tyrosine kinase receptor by nerve growth factor (NGF) involves complex signaling pathways. Stimulation of sphingosine kinase 1 (SphK1), the enzyme that phosphorylates sphingosine to form sphingosine-1-phosphate (S1P), is part of the functional TrkA signaling repertoire. In this paper, we report that in PC12 cells and dorsal root ganglion neurons, NGF translocates SphK1 to the plasma membrane and differentially activates the S1P receptors S1P1 and S1P2 in a SphK1-dependent manner, as determined with specific inhibitors and small interfering RNA targeted to SphK1. NGF-induced neurite extension was suppressed by down-regulation of S1P1 expression with antisense RNA. Conversely, when overexpressed in PC12 cells, transactivation of S1P1 by NGF markedly enhanced neurite extension and stimulation of the small GTPase Rac, important for the cytoskeletal changes required for neurite extension. Concomitantly, differentiation down-regulated expression of S1P2 whose activation would stimulate Rho and inhibit neurite extension. Thus, differential transactivation of S1P receptors by NGF regulates antagonistic signaling pathways that modulate neurite extension.
Department of Biochemistry, Virginia Commonwealth University School of Medicine, VCU Medical Center, Richmond 23298, USA.
Rachelle E
RE
Toman
Shawn G
SG
Payne
Kenneth R
KR
Watterson
Michael
M
Maceyka
Norman H
NH
Lee
Sheldon
S
Milstien
John W
JW
Bigbee
Sarah
S
Spiegel
D000818:Animals; D005727:Ganglia, Spinal / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism*; D016501:Neurites / Q000378:metabolism*; D016716:PC12 Cells; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D049312:Receptors, Lysophospholipid; D015533:Transcriptional Activation; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D000099157:Sphingosine Kinase
D020932:Nerve Growth Factor; D017853:Phosphotransferases (Alcohol Group Acceptor); D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D000099157:Sphingosine Kinase