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The Adenosine A1 and A2A Receptor C-termini are Necessary for Activation but not the Specificity of Downstream Signaling
  • Abhinav Jain,
  • Claire McGraw,
  • Anne Robinson
Abhinav Jain
Tulane University

Corresponding Author:[email protected]

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Claire McGraw
Tulane University
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Anne Robinson
Tulane University
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Recent efforts to determine the high-resolution crystal structures for the adenosine receptors (A1R and A2AR) 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 crystal structures obtained to date. However, the C-terminus has been identified as a location for protein-protein interactions that may be critical for physiological function of these important drug targets. Here, we determine whether the presence of the full-length C-terminus affected downstream signaling using a yeast MAPK response-based fluorescence assay. Upon ligand binding, the A1Δ291R or A2AΔ316R variants were unable to couple to human-yeast chimeric G-protein chimeras to generate a downstream signal in yeast, though full-length receptors showed native-like G-protein coupling. Further, constructs transfected into mammalian cells (HEK-293) showed similar behavior – i.e. the variants with C-terminal truncations lacked cAMP-linked signaling compared to the full-length receptors. Although the C-terminus was essential for Gα protein- associated signaling, chimeras of A1R with a C-terminus of A2AR coupled to the A1R-specific Gα (i.e. Gαi1 versus Gαs). This surprising result suggests that the C-terminus is important in signaling, but not specificity, for the interaction with Gα protein. This result has further implications in drug discovery both in enabling the experimental use of chimeras for ligand design, and in cautious interpretation of structure-based drug design based on truncated receptors.
26 Mar 2020Submitted to Biotechnology and Bioengineering
27 Mar 2020Assigned to Editor
27 Mar 2020Submission Checks Completed
28 Mar 2020Reviewer(s) Assigned
26 Apr 2020Review(s) Completed, Editorial Evaluation Pending