VCP/p97 regulates β2AR quality control during receptor biosynthesis

- The β2AR interacts with the ERAD protein VCP/p97.
- Loss of VCP leads to an accumulation of β2AR inside the cell.
- Signalling is not significantly altered by the loss of VCP.
- The role of VCP is to remove non-functional β2AR from the cell.

GPCRs form signalling complexes with other receptors as part of dimers, G proteins and effector partners. A proteomic screen to identify proteins that associate with the β2-adrenergic receptor (β2AR) identified many of components of the Endoplasmic-Reticulum-Associated Degradation (ERAD) quality control system [1], including the valosin-containing protein (VCP/p97). Here, we validated the interaction of VCP with co-expressed FLAG-β2AR, demonstrating, using an inducible expression system, that the interaction of FLAG-β2AR and VCP is not an artifact of overexpression of the β2AR per se. We knocked down VCP and noted that levels of FLAG-β2AR were increased in cells with lower VCP levels. This increase in the level of FLAG-β2AR did not lead to an increase in the level of functional receptor observed at the cell surface. Similarly, inhibition of the proteasome lead to a dramatic increase in the abundance of TAP-β2AR, while cellular responses again remained unchanged. Taken together, our data suggests that a substantial proportion of the β2AR produced is non-functional and VCP plays a key role in the maturation and trafficking of the β2AR as part of the ERAD quality control process.