This laboratory studies the mechanisms by which the thyrotropin receptor (TSHR) regulates thyroid growth and function and the mechanisms by which self-tolerance is maintained during hormonally induced growth and function. With respect to thyroid growth we have shown this involves induction of HMG CoA reductase, gerranylation of rhoA, and degradation of a p27 inhibitor of cdk and cyclin activation. We now show that this process requires TSH as a conditioner but uses Akt to mediate insulin/IGF-1-dependent growth. Akt is activated in thyroid tumor cells, whereas TSHR is inactivated, indicating its importance in unregulated growth and the importance of TSH/cAMP control of Akt to regulate normal growth. With respect to autoimmunity, we have pursued our hypothesis that autoimmune thyroid disease, diabetes, SLE, and eye disease are initiated by a target tissue change in MHC gene expression, converting normal cells to antigen presenting cells. We have shown that TGFbeta decreases MHC class I in thyrocytes using mechanisms identified for the hormones TSH and hydrocortisone and for iodide, by effects on TTF-1, and by new complexes with c-jun. We have continued to pursue the observation that ds nucleotides entering the cytoplasm of a cell can alter MHC class I and self antigen presentation and that this is associated with autoimmune disease. Among the cells studied this year are aortic and coronary artery muscle cells. The entrance of any ds nucleotides >25 bp into the cytoplasm, induced by viral infection or tissue injury, increase MHC gene expression, increase expression of genes important for antigen presentation, activate signaling genes important in autoimmune processes (NF-kappaB, Jak/Stat), and induce bystander activation of immune cells. The mechanism is different from interferon (IFN)and may be linked to atherosclerosis. We have expanded our link of the ds nucleotide action to the action and expression of the 90 kDa tumor-associated immunosuppressor, which we now show is transcriptionally regulated by TGF-beta as well as IFN. 90K is a marker of tumors and HIV infections. The 90K protein or transfection with cDNA are inducers of MHC class I expression and activate immune killer cells. We have further studied the activity of (MMI) derivatives termed tautameric cyclic thiones, which we developed. They can suppress the development of diabetes in the NOD mouse, SLE in the (NZBxNZW) model, and uveitis in an experimental mouse model. In addition to an MMI-sensitive transcription factor, the Y box protein YB-1 in humans or TSEP-1 in rats, we have shown the ds nucleotide action, IFN, and drugs regulate at the proteosome level early in the Jak/Stat and NFkappaB regulation path. We have shown the increase in MHC and antigen presenting genes can be used as a marker for single strand RNA virus infection, hepatitis and retroviruses; the tautomeric cyclic thiones inhibit this process and are antiviral. Using our Graves model we have shown (a) that overexpression of MHC class II in the target tissue is essential to the development of stimulating autoantibodies in Graves but not TSH binding inhibiting autoantibodies, (b) that Graves can be transfered by immune cells, and (c) that immune cell transfer is eliminated by a class I knockout. Finally, we have uncovered a novel role of follicular thyroglobulin (TG) as a feedback suppressor of thyroid-specific transcription factors and thyroid-specific genes. We have now shown that suppression involves the apical membrane asialoglycoprotein receptor, that it can be regulated by phosphorylation of serine/threonine residues, and that it is mimicked by the amino-terminal 60K of the TG molecule containing serine/threonine phosphate and a uniquely formed thyroid hormone site. We show it involves decreasing NF-1 binding to the promoters being down regulated. We have extended TG suppression to the VEGF/VGF gene but have have shown that TG upregulates pendrin, the apical iodide porter, and MHC class I. The former is associated with increased iodide transport to the follicular lumen in Graves; the latter with autoimmune phenomena in nontoxic nodular goiter.We have also shown, now, that TTF-1 present in anterior pituitary cells can act as a calcium sensor , regulates genes that control hormone synthesis and release. We hypothesize this phenomenon is important for the resynthesis of hormones and neurotropic factors whose release from cells is calcium dependent, including the release of pituitary hormones such as TSH, LH, and FSH.
