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Principles and determinants of G-protein coupling by the rhodopsin-like thyrotropin receptor

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Item Type:Article
Title:Principles and determinants of G-protein coupling by the rhodopsin-like thyrotropin receptor
Creators Name:Kleinau, G. and Jaeschke, H. and Worth, C.L. and Mueller, S. and Gonzalez, J. and Paschke, R. and Krause, G.
Abstract:In this study we wanted to gain insights into selectivity mechanisms between G-protein-coupled receptors (GPCR) and different subtypes of G-proteins. The thyrotropin receptor (TSHR) binds G-proteins promiscuously and activates both Gs (cAMP) and Gq (IP). Our goal was to dissect selectivity patterns for both pathways in the intracellular region of this receptor. We were particularly interested in the participation of poorly investigated receptor parts.We systematically investigated the amino acids of intracellular loop (ICL) 1 and helix 8 using site-directed mutagenesis alongside characterization of cAMP and IP accumulation. This approach was guided by a homology model of activated TSHR in complex with heterotrimeric Gq, using the X-ray structure of opsin with a bound G-protein peptide as a structural template.We provide evidence that ICL1 is significantly involved in G-protein activation and our model suggests potential interactions with subunits G alpha as well as G betagamma. Several amino acid substitutions impaired both IP and cAMP accumulation. Moreover, we found a few residues in ICL1 (L440, T441, H443) and helix 8 (R687) that are sensitive for Gq but not for Gs activation. Conversely, not even one residue was found that selectively affects cAMP accumulation only. Together with our previous mutagenesis data on ICL2 and ICL3 we provide here the first systematically completed map of potential interfaces between TSHR and heterotrimeric G-protein. The TSHR/Gq-heterotrimer complex is characterized by more selective interactions than the TSHR/Gs complex. In fact the receptor interface for binding Gs is a subset of that for Gq and we postulate that this may be true for other GPCRs coupling these G-proteins. Our findings support that G-protein coupling and preference is dominated by specific structural features at the intracellular region of the activated GPCR but is completed by additional complementary recognition patterns between receptor and G-protein subtypes.
Keywords:Alanine, COS Cells, Catalytic Domain, Cell Separation, Computational Biology, Cyclic AMP, Inositol Phosphates, Molecular Models, Mutation, Tertiary Protein Structure, G-Protein-Coupled Receptors, Rhodopsin, Thyrotropin, Animals, Cercopithecus aethiops
Source:PLoS ONE
Publisher:Public Library of Science
Page Range:e9745
Date:18 March 2010
Official Publication:https://doi.org/10.1371/journal.pone.0009745
PubMed:View item in PubMed

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