title: A newly discovered TSHR variant (L665F) associated with nonautoimmune hyperthyroidism in an Austrian family induces constitutive TSHR activation by steric repulsion between TM1 and TM7.
abstract: OBJECTIVE
  New in vivo mutations in G protein-coupled receptors open opportunities for insights into the mechanism of receptor activation. Here we describe the molecular mechanism of constitutive TSH receptor (TSHR) activation in an Austrian family with three generations of familial nonautoimmune hyperthyroidism.
  
  
  METHODS
  The index patient was diagnosed with hyperthyroidism during her first pregnancy. Her first two children were diagnosed with hyperthyroidism at the age of 11 and 10 years, respectively. TSH suppression was also observed in the third child at the age of 8 years, who has normal free T4 levels until now. TSH suppression in infancy was observed in the fourth child. The mother of the index patient was diagnosed with toxic multinodular goiter at the age of 36 years.
  
  
  METHODS
  DNA was extracted from blood samples from the index patient, her mother, and her four children. Screening for TSHR mutations was performed by high-resolution melting assays and subsequent sequencing. Elucidation of the underlying mechanism of TSHR activation was carried out by generation and structural analysis of TSHR transmembrane homology models and verification of model predictions by functional characterization of receptor mutations.
  
  
  CONCLUSIONS
  A newly discovered TSHR mutation L665F in transmembrane helix 7 of the receptor was detected in six members of this family. Functional characterization of L665F revealed constitutive activation for the Gs pathway and thus represents the molecular cause for hyperthyroidism in this family. The constitutive activation is possibly linked to a steric clash introduced by the L665F mutation between transmembrane helices 1 and 7.
authors.affiliation: Department of Internal Medicine, Endocrinology, and Nephrology (H.J., J.S., M.E., S.H., R.Pa.), University of Leipzig, 04103 Leipzig, Germany; Department of Pediatrics (R.Pu., O.R.), University Hospital Salzburg, 5020 Salzburg, Austria; and Center for Structural Biology (J.M.), Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: Holger
authors.initials: H
authors.lastname: Jaeschke
authors.forename: Joerg
authors.initials: J
authors.lastname: Schaarschmidt
authors.forename: Markus
authors.initials: M
authors.lastname: Eszlinger
authors.forename: Sandra
authors.initials: S
authors.lastname: Huth
authors.forename: Rudolf
authors.initials: R
authors.lastname: Puttinger
authors.forename: Olaf
authors.initials: O
authors.lastname: Rittinger
authors.forename: Jens
authors.initials: J
authors.lastname: Meiler
authors.forename: Ralf
authors.initials: R
authors.lastname: Paschke
mesh_terms: D000328:Adult; D001317:Austria; D001483:Base Sequence; D005192:Family Health; D005260:Female; D006044:Goiter, Nodular / Q000235:genetics*; D006801:Humans; D006980:Hyperthyroidism / Q000151:congenital* / Q000235:genetics; D010375:Pedigree; D017354:Point Mutation; D011247:Pregnancy; D011248:Pregnancy Complications / Q000235:genetics*; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000235:genetics*; D013237:Stereoisomerism
chemical_list: D011989:Receptors, Thyrotropin