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Biomedicines

Title:		"The Specificity of Downstream Signaling for A(1) and A(2A)R Does Not Depend on the C-Terminus, Despite the Importance of This Domain in Downstream Signaling Strength"
Author(s):		Jain AR; McGraw C; Robinson AS;
Address:		"Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA. Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA"
Journal Title:		Biomedicines
Year:		2020
Volume:		20201213
Issue:		12
Page Number:		-
DOI:		10.3390/biomedicines8120603
ISSN/ISBN:		2227-9059 (Print) 2227-9059 (Electronic) 2227-9059 (Linking)
Abstract:		"Recent efforts to determine the high-resolution crystal structures for the adenosine receptors (A(1)R and A(2A)R) have utilized modifications to the native receptors in order to facilitate receptor crystallization and structure determination. One common modification is a truncation of the unstructured C-terminus, which has been utilized for all the adenosine receptor crystal structures obtained to date. Ligand binding for this truncated receptor has been shown to be similar to full-length receptor for A(2A)R. However, the C-terminus has been identified as a location for protein-protein interactions that may be critical for the physiological function of these important drug targets. We show that variants with A(2A)R C-terminal truncations lacked cAMP-linked signaling compared to the full-length receptor constructs transfected into mammalian cells (HEK-293). In addition, we show that in a humanized yeast system, the absence of the full-length C-terminus affected downstream signaling using a yeast MAPK response-based fluorescence assay, though full-length receptors showed native-like G-protein coupling. To further study the G protein coupling, we used this humanized yeast platform to explore coupling to human-yeast G-protein chimeras in a cellular context. Although the C-terminus was essential for Galpha protein-associated signaling, chimeras of A(1)R with a C-terminus of A(2A)R coupled to the A(1)R-specific Galpha (i.e., Galphai1 versus Galphas). This surprising result suggests that the C-terminus is important in the signaling strength, but not specificity, of the Galpha protein interaction. This result has further implications in drug discovery, both in enabling the experimental use of chimeras for ligand design, and in the cautious interpretation of structure-based drug design using truncated receptors"
Keywords:		C-terminus G protein G protein-coupled receptors adenosine receptor receptor chimera yeast pheromone response;
Notes:		"PubMed-not-MEDLINEJain, Abhinav R McGraw, Claire Robinson, Anne S eng R01GM120351/NH/NIH HHS/ N/A/Catherine and Henry Boh Endowment/ Switzerland 2020/12/17 Biomedicines. 2020 Dec 13; 8(12):603. doi: 10.3390/biomedicines8120603"