title: Gremlin utilizes canonical and non-canonical TGFβ signaling to induce lysyl oxidase (LOX) genes in human trabecular meshwork cells.
abstract: The TGFβ/BMP signaling pathways are involved in glaucomatous damage to the trabecular meshwork (TM) leading to elevated intraocular pressure (IOP), which is a major risk factor for the development and progression of glaucoma. The BMP antagonist gremlin is elevated in glaucomatous TM cells and tissues and can directly elevate IOP. Gremlin utilizes the TGFβ2/SMAD pathway to induce TM extracellular matrix (ECM) proteins. The purpose of this study is to determine whether expression of the ECM cross-linking lysyl oxidase (LOX) genes is regulated by gremlin in cultured human TM cells. Human TM cells were treated with recombinant gremlin, and expression of the LOX genes was examined by quantitative RT-PCR and western immunoblotting. TM cells were pretreated with TGFBR inhibitors (LY364947 or SB431542), an inhibitor of the SMAD signaling pathway (SIS3), or with JNK (SP600125) and p38 MAPK (SB203580) inhibitors to identify the signaling pathway(s) involved in gremlin induction of LOX protein expression. All five LOX genes (LOX and LOXL1-4) were induced by gremlin. Gremlin induction of LOX genes and protein expression was blocked by TGFBR inhibitors as well as by inhibitors of the SMAD3, JNK and p38 MAPK signaling pathways. We conclude that gremlin employs both canonical TGFβ/SMAD and the non-canonical JNK and p38 MAPK signaling pathways to induce LOX genes and proteins in cultured human TM cells. Increased LOX levels may be at least partially responsible for gremlin-mediated IOP elevation and increased aqueous humor outflow resistance leading to glaucoma.
authors.affiliation: Department of Cell Biology & Anatomy, 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.forename: Robert J
authors.initials: RJ
authors.lastname: Wordinger
authors.forename: Abbot F
authors.initials: AF
authors.lastname: Clark
mesh_terms: D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005109:Extracellular Matrix / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D010766:Phosphorylation; D008249:Protein-Lysine 6-Oxidase / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors; D014129:Trabecular Meshwork / Q000187:drug effects* / Q000201:enzymology; D053781:Transforming Growth Factor beta2 / Q000378:metabolism*
chemical_list: D019485:Bone Morphogenetic Proteins; C486399:GREM1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2; D008249:Protein-Lysine 6-Oxidase
keywords: extracellular matrix; gremlin; lysyl oxidase; lysyl oxidase like; primary open angle glaucoma; trabecular meshwork; transforming growth factor beta