ECE2011 Poster Presentations Signal transduction (4 abstracts)
Different and common transmembrane activation mechanisms between glycoprotein hormone receptors and other G-protein coupled receptors
I Hoyer 1 , G Kleinau 1, , A K Haas 1 , A Kreuchwig 1 , P Grzesik 1 , C L Worth 1, , R Schuelein 1 & G Krause 1
1Leibniz-Institut für molekulare Pharmakologie, Berlin, Germany; 2Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin, Berlin, Germany; 3Institute of Physiology, Charité Universitätsmedizin, Berlin, Germany.
The aim of our study is to identify signalling sensitive residue positions of the glycoprotein hormone receptors (GPHR), especially the thyrotropin receptor (TSHR) on the transmembrane helices (TMH) 5 and 6, knowing to be involved in GPCR activation. We performed modelling driven site-directed mutagenesis to pinpoint residues that are responsible for stabilization of active and inactive conformations of the TSHR.
We highlight two amino acids that are highly conserved in other family A GPCRs but are different in the GPHRs. Proline at position 5.50 causes a conformational-twist in TMH5 at all available GPCR X-ray structures. This proline is replaced in GPHRs by an alanine. However, mutation of alanine to proline at position 5.50 (TSHR-A593P) results in a 20-fold decreased cell surface expression and a folding defect of TSHR. This implies structural consequences because of different interactions between TMH5 and neighbouring helices 3, 4, and 6 in the TSHR compared to other GPCRs. Our results favour for TSHR and homologous FSHR and LHCGR rather a regular alpha-helix conformation than a proline-twisted conformation of TMH5.
Position 6.48 that is highly conserved in other family A GPCRs by a tryptophan known as a ‘toggle switch’ is replaced in GPHR by a methionine. Substitution of this methionine by tryptophan (TSHR-M637W) results in constitutive activation and indicates an alternative micro-switch at TSHR position 6.48.
Our functional data highlight the importance of hydrophobic amino acids at the interface between TMH5 and 6. We confirmed this hypothesis by a statistical analysis of residue properties between the TMHs of a vast number of family A GPCR sequences. We revealed that interacting polar residues between TMH2, 3, 6 and 7 likely constrain the inactive conformation, whereas their release plus the formation of hydrophobic interactions between TMH5 and 6 may constrain the active state conformation of GPCRs and also of GPHRs.
Article tools
My recent searches
My recently viewed abstracts
Authors
Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
© Bioscientifica 2024 |
Privacy policy |
Cookie settings
BiosciAbstracts
Bioscientifica Abstracts is the gateway to a series of products that provide a permanent, citable record of abstracts for biomedical and life science conferences.
Find out more