Latent transforming growth factor binding protein 4 regulates transforming growth factor beta receptor stability
Journal
Human Molecular Genetics
Journal Volume
24
Journal Issue
14
Pages
4024-4036
Date Issued
2015
Author(s)
Lawrence E.C.
Levine K.L.
Dabovic B.
Jung C.
Davis E.C.
Madan-Khetarpal S.
Urban Z.
Abstract
Mutations in the gene for the latent transforming growth factor beta binding protein 4 (LTBP4) cause autosomal recessive cutis laxa type 1C. To understand the molecular disease mechanisms of this disease, we investigated the impact of LTBP4 loss on transforming growth factor beta (TGFβ) signaling. Despite elevated extracellular TGFβ activity, downstream signaling molecules of the TGFβ pathway, including pSMAD2 and pERK, were down-regulated in LTBP4 mutant human dermal fibroblasts. In addition, TGFβ receptors 1 and 2 (TGFBR1 and TGFBR2) were reduced at the protein but not at the ribonucleic acid level. Treatment with exogenous TGFβ1 led to an initially rapid increase in SMAD2 phosphorylation followed by a sustained depression of phosphorylation and receptor abundance. In mutant cells TGFBR1 was co-localized with lysosomes. Treatment with a TGFBR1 kinase inhibitor, endocytosis inhibitors or a lysosome inhibitor, normalized the levels of TGFBR1 and TGFBR2. Co-immunoprecipitation demonstrated a molecular interaction between LTBP4 and TGFBR2. Knockdown of LTBP4 reduced TGFβ receptor abundance and signaling in normal cells and supplementation of recombinant LTBP4 enhanced these measures in mutant cells. In a mouse model of Ltbp4 deficiency, reduced TGFβ signaling and receptor levels were normalized upon TGFBR1 kinase inhibitor treatment. Our results show that LTBP4 interacts with TGFBR2 and stabilizes TGFβ receptors by preventing their endocytosis and lysosomal degradation in a ligand-dependent and receptor kinase activity-dependent manner. These findings identify LTBP4 as a key molecule required for the stability of the TGFβ receptor complex, and a new mechanism by which the extracellular matrix regulates cytokine receptor signaling. ? The Author 2015. Published by Oxford University Press. All rights reserved.
SDGs
Other Subjects
latent transforming growth factor beta binding protein; latent transforming growth factor beta binding protein 4; messenger RNA; Smad2 protein; transforming growth factor beta receptor; transforming growth factor beta receptor 1; transforming growth factor beta receptor 2; unclassified drug; latent transforming growth factor beta binding protein; LTBP4 protein, human; protein serine threonine kinase; Smad2 protein; SMAD2 protein, human; TGF-beta type I receptor; transforming growth factor beta receptor; transforming growth factor-beta type II receptor; adolescent; adult; animal tissue; Article; autosomal recessive cutis laxa type 1c; autosomal recessive disorder; cell mutant; cellular distribution; child; clinical article; controlled study; cutis laxa; down regulation; endocytosis; female; fibroblast; frameshift mutation; gene control; gene loss; gene silencing; human; human cell; immunoprecipitation; in vivo study; intracellular signaling; loss of function mutation; lysosome; male; missense mutation; mouse; nonhuman; nonsense mutation; preschool child; priority journal; protein degradation; protein phosphorylation; protein protein interaction; protein stability; splicing defect; young adult; animal; case control study; cell culture; cutis laxa; cytology; disease model; genetics; knockout mouse; metabolism; mutation; phosphorylation; signal transduction; Animals; Case-Control Studies; Cells, Cultured; Cutis Laxa; Disease Models, Animal; Down-Regulation; Endocytosis; Female; Fibroblasts; Humans; Immunoprecipitation; Latent TGF-beta Binding Proteins; Male; Mice; Mice, Knockout; Mutation; Phosphorylation; Protein-Serine-Threonine Kinases; Receptors, Transforming Growth Factor beta; Signal Transduction; Smad2 Protein
Publisher
Oxford University Press
Type
journal article