Sphingosine kinase 1 (SPHK1) is induced by transforming growth factor-beta and mediates TIMP-1 up-regulation.
Transforming growth factor-beta (TGF-beta) signaling plays a pivotal role in extracellular matrix deposition by stimulating collagen production and other extracellular matrix proteins and by inhibiting matrix degradation. The present study was undertaken to define the role of sphingosine kinase (SphK) in TGF-beta signaling. TGF-beta markedly up-regulated SphK1 mRNA and protein amounts and caused a prolonged increase in SphK activity in dermal fibroblasts. Concomitantly, TGF-beta reduced sphingosine-1-phosphate phosphatase activity. Consistent with the changes in enzyme activity, corresponding changes in sphingolipid levels were observed such that sphingosine 1-phosphate (S1P) was increased (approximately 2-fold), whereas sphingosine and ceramide were reduced after 24 h of TGF-beta treatment. Given the relatively early induction of SphK gene expression in response to TGF-beta, we examined whether SphK1 may be involved in the regulation of TGF-beta-inducible genes that exhibit compatible kinetics, e.g. tissue inhibitor of metalloproteinase-1 (TIMP-1). We demonstrate that decreasing SphK1 expression by small interfering RNA (siRNA) blocked TGF-beta-mediated up-regulation of TIMP-1 protein suggesting that up-regulation of SphK1 contributes to the induction of TIMP-1 in response to TGF-beta. The role of SphK1 as a positive regulator of TIMP-1 gene expression was further corroborated by using ectopically expressed SphK1 in the absence of TGF-beta. Adenovirally expressed SphK1 led to a 2-fold increase of endogenous S1P and to increased TIMP-1 mRNA and protein production. In addition, ectopic SphK1 and TGF-beta cooperated in TIMP-1 up-regulation. Mechanistically, experiments utilizing TIMP-1 promoter constructs demonstrated that the action of SphK1 on the TIMP-1 promoter is through the AP1-response element, consistent with the SphK1-mediated up-regulation of phospho-c-Jun levels, a key component of AP1. Together, these experiments demonstrate that SphK/S1P are important components of the TGF-beta signaling pathway involved in up-regulation of the TIMP-1 gene.
Yamanaka
Masayoshi
M
Division of Rheumatology and Immunology, Medical University of South Carolina, Charleston, SC 29725, USA.
Shegogue
Daniel
D
Pei
Heuping
H
Bu
Shizhong
S
Bielawska
Alicja
A
Bielawski
Jacek
J
Pettus
Benjamin
B
Hannun
Yusuf A
YA
Obeid
Lina
L
Trojanowska
Maria
M
D000256:Adenoviridae / Q000235:genetics; D002518:Ceramides / Q000032:analysis; D004790:Enzyme Induction; D005347:Fibroblasts / Q000201:enzymology; D005786:Gene Expression Regulation / Q000502:physiology*; D005822:Genetic Vectors; D006801:Humans; D007700:Kinetics; D008246:Lysophospholipids / Q000032:analysis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000032:analysis; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D000099157:Sphingosine Kinase
D002518:Ceramides; D008246:Lysophospholipids; D008565:Membrane Proteins; D010744:Phosphoric Monoester Hydrolases; D017853:Phosphotransferases (Alcohol Group Acceptor); D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013110:Sphingosine; D019715:Tissue Inhibitor of Metalloproteinase-1; D016212:Transforming Growth Factor beta; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C498527:SGPP1 protein, human; C401298:sphingosine-1-phosphate phosphatase