THYROID IODIDE TRANSPORTER - LOCAL SEQUENCE HOMOLOGIES WITH THYROID AUTOANTIGENS

Here we show the existence of local amino acid (aa) sequence homologie s between rat thyroid iodide transporter (Na+/I- symporter or NIS), wh ose gene was recently cloned, and known human thyroid autoantigens [th yroglobulin (Tg), thyroid peroxidase (TPO) and thyrotropin receptor (T SHR)] NIS sequences corresponding to the fourth (aa 264-282) and fifth extracellular loop (aa 386-414) are 15 to 40% identical and 30 to 60% similar to sequences corresponding to known or putative epitopes of T g, TPO and TSHR. The sixth extracellular loop (aa 465-485) beared homo logy (44%, identity, 52% similarity) only to a region of Tg which flan ks one of its immunodominant domains. Sequences of thyroid autoantigen s other than NIS shared homology, especially Tg and TPO. We conclude t hat in all likelihood NIS is an additional thyroid antigen, which shar es common epitopes with the other thyroid autoantigens. Addendum: A st udy in abstract form appeared after submission of our paper finds expe rimental evidence for the antigenicity of two extracellular segments ( aa 262-280 and 468-487) and of a portion of the intracellular C-termin us (aa 560-579). (C)1997, Editrice Kurtis.