Characterization of the α1D‐Adrenergic Receptor Signalosome

Abstract

Previously, we reported the identification of syntrophins as novel accessory proteins for α1D‐adrenergic receptors (ARs). Syntrophins are members of the dystrophin complex, and act as scaffolds for anchoring membrane proteins to cytoskeletal proteins. To characterize the functional importance of this interaction, we examined how syntrophins contribute to α1D‐AR function in vitro and in vivo. In vitro, syntrophins increase α1D‐AR binding site density and functional coupling in HEK293 cells. In vivo, α‐ and β2‐syntrophin double knock‐out mice have significantly diminished α1D‐AR functional responses in comparison to wild type mice. Taken together, these findings suggest that syntrophins play an essential role for α1D‐AR function in vivo, presumably by anchoring α1D‐ARs in the plasma membrane as a functional signalosome, and by recruiting necessary components into the signalosome. Next, we determined what proteins syntrophins recruit to the α1D‐AR signalosome, by performing tandem affinity purification (TAP)/mass spectrometry on α1D‐AR, α/β1/β2‐syntrophin, and α‐dystrobrevin‐1/2. Our data revealed both previously identified and novel proteins recruited to the α1D‐AR/syntrophin signalosome. Current experiments are examining how these recruited proteins contribute to α1D‐AR function in vivo. Research was supported in part by PHS NRSA T32 GM07270 from NIGMS.