title: Quantitative analysis of TGFBR2 mutations in Marfan-syndrome-related disorders suggests a correlation between phenotypic severity and Smad signaling activity.
abstract: Mutations in the gene encoding transforming growth factor-beta receptor type II (TGFBR2) have been described in patients with Loeys-Dietz syndrome (LDS), Marfan syndrome type 2 (MFS2) and familial thoracic aortic aneurysms and dissections (TAAD). Here, we present a comprehensive and quantitative analysis of TGFBR2 expression, turnover and TGF-β-induced Smad and ERK signaling activity for nine mutations identified in patients with LDS, MFS2 and TAAD. The mutations had different effects on protein stability, internalization and signaling. A dominant-negative effect was demonstrated for mutations associated with LDS and MFS2. No mutation showed evidence of an immediate cell-autonomous paradoxical activation of TGF-β signaling. There were no cell biological differences between mutations described in patients with LDS and MFS2. By contrast, R460C, which has been found in familial TAAD but not in MFS2 or LDS, showed a less-severe dominant-negative effect and retained residual Smad phosphorylation and transcriptional activity. TAAD is characterized primarily by thoracic aortic aneurysms or dissections. By contrast, MFS2 is characterized by numerous skeletal abnormalities, and patients with LDS additionally can display craniofacial and other abnormalities. Therefore, our findings suggest that the balance between defects in Smad and ERK signaling might be an important determinant of phenotypic severity in disorders related to mutations in TGFBR2.
authors.affiliation: Institute for Chemistry-Biochemistry, Freie Universität Berlin, Berlin, 14195, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Horbelt
authors.forename: Gao
authors.initials: G
authors.lastname: Guo
authors.forename: Peter N
authors.initials: PN
authors.lastname: Robinson
authors.forename: Petra
authors.initials: P
authors.lastname: Knaus
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004705:Endocytosis; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008382:Marfan Syndrome / Q000235:genetics* / Q000473:pathology*; D008907:Mink; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000737:chemistry / Q000235:genetics*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D008156:Luciferases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II