Dystroglycan Is Present in Rat Thyroid and Rat Thyroid Cells and Responds to Thyrotropin1

Dystroglycan is a high affinity laminin-binding glycoprotein originally described as a member of the dystrophin-associated glycoprotein complex in muscle. We have demonstrated the presence of dystroglycan in the thyroid using immunocytochemistry, immunoblots, ligand binding assays, and relative quantitative RT-PCR. In intact rat thyroid glands, antibodies against the α (extracellular, laminin-binding subunit) andβ (cytoplasmic/membrane bound) portions of the dystroglycan protein reacted at basolateral membranes where they colocalized with laminin. Western-blotted protein from the Fischer rat thyroid cell line FRTL-5 reacted with both the α- and β-dystroglycan antibodies. Theα -dystroglycan-reactive band colocalized with laminin-binding activity, and the protein and binding activity were decreased by TSH. In contrast, in the culture medium of these cells, α-dystroglycan was increased by TSH. The β-dystroglycan antibody recognized the full-length 43-kDa band and an approximately 30-kDa truncated form. The t...