title: Crosstalk between TGFβ and Wnt signaling pathways in the human trabecular meshwork.
abstract: Primary Open Angle Glaucoma (POAG) is an irreversible, vision-threatening disease that affects millions worldwide. The principal risk factor of POAG is increased intraocular pressure (IOP) due to pathological changes in the trabecular meshwork (TM). The TGFβ signaling pathway activator TGFβ2 and the Wnt signaling pathway inhibitor secreted frizzled-related protein 1 (sFRP1) are elevated in the POAG TM. In this study, we determined whether there is a crosstalk between the TGFβ/Smad pathway and the canonical Wnt pathway using luciferase reporter assays. Lentiviral luciferase reporter vectors for studying the TGFβ/Smad pathway or the canonical Wnt pathway were transduced into primary human non-glaucomatous TM (NTM) cells. Cells were treated with or without a combination of 5 μg/ml TGFβ2 and/or 100 ng/ml Wnt3a recombinant proteins, and luciferase levels were measured using a plate reader. We found that TGFβ2 inhibited Wnt3a-induced canonical Wnt pathway activation, while Wnt3a inhibited TGFβ2-induced TGFβ/Smad pathway activation (n = 6, p < 0.05) in 3 NTM cell strains. We also found that knocking down of Smad4 or β-catenin using siRNA in HTM5 cells transfected with similar luciferase reporter plasmids abolished the inhibitory effect of TGFβ2 and/or Wnt3a on the other pathway (n = 6). Our results suggest the existence of a cross-inhibition between the TGFβ/Smad and canonical Wnt pathways in the TM, and this cross-inhibition may be mediated by Smad4 and β-catenin.
authors.affiliation: North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA.
authors.forename: Hannah C
authors.initials: HC
authors.lastname: Webber
authors.affiliation: North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA.
authors.forename: Jaclyn Y
authors.initials: JY
authors.lastname: Bermudez
authors.affiliation: North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA.
authors.forename: Anirudh
authors.initials: A
authors.lastname: Sethi
authors.affiliation: North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA.
authors.forename: Abbot F
authors.initials: AF
authors.lastname: Clark
authors.affiliation: North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Blvd, Fort Worth, TX 76107, USA. Electronic address: Weiming.mao@unthsc.edu.
authors.forename: Weiming
authors.initials: W
authors.lastname: Mao
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D005260:Female; D005902:Glaucoma, Open-Angle / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D015398:Signal Transduction / Q000502:physiology; D051901:Smad4 Protein / Q000378:metabolism; D014129:Trabecular Meshwork / Q000378:metabolism*; D053781:Transforming Growth Factor beta2 / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D060449:Wnt Signaling Pathway / Q000502:physiology*; D060509:Wnt3A Protein / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D051176:beta Catenin / Q000378:metabolism
chemical_list: D051901:Smad4 Protein; D053781:Transforming Growth Factor beta2; D060509:Wnt3A Protein; D051176:beta Catenin; D008156:Luciferases
keywords: Crosstalk; Glaucoma; Smad4; TGFβ signaling; Trabecular meshwork; Wnt signaling; β-catenin