G-protein coupled receptors: Overcoming challenges to expression and biophysical characterization of adenosine receptors
The adenosine receptor subfamily of G-protein coupled receptors is an important family of membrane receptors that modulate blood pressure, and more recently have been implicated in cancer, neurodegenerative diseases, and diabetes. This talk will focus on two aspects related to adenosine receptors – characterizing binding of adenosine A2A receptor (A2AR) to its cognate G-protein and improving expression of adenosine A1 receptor (A1R) via protein chimera engineering.
Full-length A2AR has been shown to interact with the stimulatory G protein alpha subunit (Gsα) to activate downstream signaling. Previous work in our lab revealed that truncation of the C-terminus reduced the downstream signaling response in mammalian cells. In this talk I will describe the use of surface plasmon resonance (SPR) to determine the effects of the A2AR C-terminus on the protein-protein interaction. We found A2AD316R was capable of binding Gαs, but with a significantly decreased Bmax as well as a significantly decreased receptor association rate and increased dissociation rate. Together our results suggest that loss of cAMP-related signaling may result from a reduced level of GPCR-G protein complexes as well as rapid turnover of the complexes. Interestingly, the adenosine A2A receptor (A2AR) has a longer C-terminus than the other adenosine receptor subtypes, which may contribute to its exceptional trafficking to the plasma membrane. To test the possibility to improve trafficking of A1R, chimeric receptors with A2AR were constructed. The chimeric A1/A2AR receptor showed improved localization to the plasma membrane and was functionally active, with greater than three-fold higher yields than previously reported from other heterologous expression systems. Together, these approaches should facilitate biophysical characterization and drug discovery efforts.