title: Opposite effects of dihydrosphingosine 1-phosphate and sphingosine 1-phosphate on transforming growth factor-beta/Smad signaling are mediated through the PTEN/PPM1A-dependent pathway.
abstract: Transforming growth factor-beta (TGF-beta) is an important regulator of physiological connective tissue biosynthesis and plays a central role in pathological tissue fibrosis. Previous studies have established that a biologically active lipid mediator, sphingosine 1-phosphate (S1P), mimics some of the profibrotic functions of TGF-beta through cross-activation of Smad signaling. Here we report that another product of sphingosine kinase, dihydrosphingosine 1-phosphate (dhS1P), has an opposite role in the regulation of TGF-beta signaling. In contrast to S1P, dhS1P inhibits TGF-beta-induced Smad2/3 phosphorylation and up-regulation of collagen synthesis. The effects of dhS1P require a lipid phosphatase, PTEN, a key modulator of cell growth and survival. dhS1P stimulates phosphorylation of the C-terminal domain of PTEN and its subsequent translocation into the nucleus. We demonstrate a novel function of nuclear PTEN as a co-factor of the Smad2/3 phosphatase, PPM1A. Complex formation of PTEN with PPM1A does not require the lipid phosphatase activity but depends on phosphorylation of the serine/threonine residues located in the C-terminal domain of PTEN. Upon complex formation with PTEN, PPM1A is protected from degradation induced by the TGF-beta signaling. Consequently, overexpression of PTEN abrogates TGF-beta-induced Smad2/3 phosphorylation. This study establishes a novel role for nuclear PTEN in the stabilization of PPM1A. PTEN-mediated cross-talk between the sphingolipid and TGF-beta signaling pathways may play an important role in physiological and pathological TGF-beta signaling.
authors.affiliation: Division of Rheumatology and Immunology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Shizhong
authors.initials: S
authors.lastname: Bu
authors.forename: Bagrat
authors.initials: B
authors.lastname: Kapanadze
authors.forename: Tien
authors.initials: T
authors.lastname: Hsu
authors.forename: Maria
authors.initials: M
authors.lastname: Trojanowska
mesh_terms: D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival; D003094:Collagen / Q000096:biosynthesis; D004795:Enzyme Stability; D005355:Fibrosis; D006801:Humans; D008246:Lysophospholipids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism*; D051900:Smad3 Protein / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D008246:Lysophospholipids; D009097:Multienzyme Complexes; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; C060504:dihydrosphingosine 1-phosphate; C060506:sphingosine 1-phosphate; D003094:Collagen; C000607456:PPM1A protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D013110:Sphingosine