Sphingosine kinase is induced in mouse 3T3-L1 cells and promotes adipogenesis.
Sphingosine 1-phosphate (S1P) is a lysophospholipid mediator that exerts numerous biological activities both as a receptor ligand and as an intracellular second messenger. In the present study, we explored roles of sphingosine kinase (SphK), an S1P-producing enzyme, in adipose tissue. We utilized mouse 3T3-L1 cells as an in vitro model of adipogenesis, using a mixture of insulin/dexamethasone/3-isobutyl-1-methylxanthine (IBMX) to induce differentiation. Real-time quantitative PCR (qRT-PCR) assays revealed that the expression levels of transcripts encoding both isoforms of SphK-1 and SphK-2 are up-regulated during adipogenesis (37.6- and 6.6-fold vs. basal, P < 0.05, respectively). Concomitantly, SphK-1/SphK-2 protein abundance and S1P contents of these cells increased at 3 days after hormonal stimulation. Loss-of-function approaches by pharmacological inhibition of SphK activity as well as by transfection with small interfering RNA (siRNA) against SphK-1 led to significant attenuation of lipid droplet accumulation and adipocyte marker gene expression. We detected marked elevation of SphK-1 mRNA in adipose tissue derived from 13-week-old ob/ob mice with obese phenotype than their lean littermates. These results suggest that increased expression of SphK, an S1P-producing enzyme, plays a significant role during adipogenesis, potentially providing a novel point of control in adipose tissue.
Hashimoto
Takeshi
T
Department of Cardiovascular Physiology, Kagawa University Faculty of Medicine, Kagawa, Japan 761-0793.
Igarashi
Junsuke
J
Kosaka
Hiroaki
H
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D050156:Adipogenesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004790:Enzyme Induction; D015870:Gene Expression; D008246:Lysophospholipids / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D013110:Sphingosine / Q000031:analogs & derivatives / Q000096:biosynthesis; D014162:Transfection; D000099157:Sphingosine Kinase
D017931:DNA Primers; D008246:Lysophospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate