The Human TSHβ Subunit Proteins and Their Binding Sites on the TSH Receptor Using Molecular Dynamics Simulation

Abstract

To gain further insight into the binding of the normal and variant human TSHβ subunits (TSHβ & TSHβv), we modeled the two monomeric proteins and studied their interaction with the TSH receptor ectodomain (TSHR-ECD) using molecular dynamics simulation Furthermore, analyzed their bioactivity in vitro using recombinant proteins to confirm that such binding was physiologically relevant. Examining the interaction of TSHβ and TSHβv with the TSHR-ECD model using molecular dynamic simulation revealed strong binding of these proteins to the receptor ECD. The specificity of TSHβ and TSHβv binding to the TSHR-ECD was examined by analyzing the hydrogen-bonding residues of these subunits to the FSH receptor ECD indicating the inability of these molecules to bind to the FSH receptors. Furthermore, the modelling suggests that TSHβ and TSHβv proteins clasped the concave surface of the leucine rich region (LRR) of the TSHR ECD in a similar way to the native TSH using dynamic hydrogen bonding. These mutually exclusive stable interactions between the subunits and ECD residues included some high affinity contact sites corresponding to binding-models of native TSH. Furthermore, we cloned TSHβ and TSHβv proteins using the entire coding ORF and purified the flag-tagged proteins. The expressed TSHβ subunit proteins retained bioactivity both in a co-culture system as well as with immune-purified proteins. In summary, we showed that such interactions can result in a functional outcome and may exert physiological or pathophysiological effects in immune cells.

Unconventional Actions of Glycoprotein Hormone Subunits: A Comprehensive Review

“…And accordingly, both forms were shown to elicit a response as recombinant monomers on cells expressing the TSHR ( 197 , 201 , 202 ). But for the TSHβ variant to activate the receptor, it needs to be secreted and that was not shown for the recombinant variant peptide as a monomer ( 201 ). Release of the TSHβ variant was reported from naturally expressing cells or transfected cells but the released amount appeared to be very low.…”

“…It seems thus very unlikely that this truncated variant may associate with an α subunit to generate a dimer able to activate the TSHR. Yet, molecular dynamics simulation of monomeric TSHβ subunits in complex with the extracellular domain of the TSHR seems to indicate that the full-length β subunit and the truncated peptide dock in a rather similar way ( 200 , 201 ). And accordingly, both forms were shown to elicit a response as recombinant monomers on cells expressing the TSHR ( 197 , 201 , 202 ).…”

“…Yet, molecular dynamics simulation of monomeric TSHβ subunits in complex with the extracellular domain of the TSHR seems to indicate that the full-length β subunit and the truncated peptide dock in a rather similar way ( 200 , 201 ). And accordingly, both forms were shown to elicit a response as recombinant monomers on cells expressing the TSHR ( 197 , 201 , 202 ). But for the TSHβ variant to activate the receptor, it needs to be secreted and that was not shown for the recombinant variant peptide as a monomer ( 201 ).…”

Thyroid: Functional Food (Family Welfare, Family Physician, Nurse, Computational Validation, and Drug Discovery)

“…The high inhibition constant with a 2-2.5 Å distance of the H bond further affirms the likeness to yield nice therapeutic results. The half-life of T3 is about 2.5 days, while the half-life of T4 is about 6.5 days (Mezei et al, 2020), while the Cinnamic group's is maximum for 75minutes (Bin et.al., 2015). Hence these whence given sublingual, daily, repeatedly optimum results are reported.…”