Davies, T. F. | bioRxiv Science

bioRxiv2022

Computational model of the full-length TSH receptor

The receptor for thyroid stimulating hormone (TSHR), a GPCR, is of particular interest as the primary antigen in autoimmune hyperthyroidism (Graves disease) caused by stimulating TSHR antibodies. To date, only one domain of the extracellular region of the TSHR has been crystallized. We have now generated a model of the entire TSHR by merging the extracellular region of the receptor, obtained using artificial intelligence, with our recent homology model of the transmembrane domain, embedded it in a lipid membrane solvated it with water and counterions, and performed 1000ns Molecular Dynamic simulations on it. The simulations showed that the structure of the transmembrane and leucine-rich domains were remarkably constant while the linking region (LR), known more commonly as the "hinge region", showed significant flexibility, forming several transient secondary structural elements. Furthermore, the relative orientation of the leucine-rich domain with the rest of the receptor was also seen to be variable. These data suggest that this linker region is an intrinsically disordered protein (IDP). Furthermore, preliminary data simulating the full TSHR model complexed with its ligand (TSH) showed that (a) there is a strong affinity between the linker region and TSH ligand and (b) the association of the linker region and the TSH ligand reduces the structural fluctuations in the linker region. This full-length model illustrates the importance of the linker region in responding to ligand binding and lays the foundation for studies of pathologic TSHR autoantibodies complexed with the TSHR to give further insight into their interaction with the flexible linker region.

biophysics↗

bioRxiv2022

Brain Atlas for Glycoprotein Hormone Receptors at Single-Transcript Level

There is increasing evidence that anterior pituitary hormones, traditionally thought to have unitary functions in regulating single endocrine targets, act on multiple somatic tissues, such as bone, fat, and liver. There is also emerging evidence for anterior pituitary hormone action on brain receptors in mediating central neural and peripheral somatic functions. Here, we have created the most comprehensive neuroanatomical atlas on the expression of TSHRs, LHCGRs and FSHRs. We have used RNAscope, a technology that allows the detection of mRNA at single-transcript level, together with protein level validation, to document Tshr expression in 173 and Fshr expression in 353 brain regions, nuclei and sub-nuclei identified using the Atlas for the Mouse Brain in Stereotaxic Coordinates. We also identified Lhcgr transcripts in 401 brain regions, nuclei and sub-nuclei. Complementarily, we used ViewRNA, another single-transcript detection technology, to establish the expression of FSHRs in human brain samples, where transcripts were co-localized in MALAT1-positive neurons. In addition, we show high expression for all three receptors in the ventricular region--with yet unknown functions. Intriguingly, Tshr and Fshr expression in the ependymal layer of the third ventricle was similar to that of the thyroid follicular cells and testicular Sertoli cells, respectively. TSHRs were expressed specifically in tanycytes. In contrast, Fshrs were localized to NeuN-positive neurons in the granular layer of the dentate gyrus in murine and human brain--both are Alzheimers disease vulnerable regions. Our atlas thus provides a vital resource for scientists to explore the link between the stimulation or inactivation of brain glycoprotein hormone receptors on somatic function. New actionable pathways for human disease may be unmasked through further studies.

neuroscience↗