Our discovery of Gpr161 as a critical negative regulator of Shh signaling provides us a unique portal for starting to understand mechanisms for ciliary activation of GPCRs. In order to describe the endogenous signals required for activation of Gpr161, it is critical to deorphanize this receptor and define the downstream effectors in its signaling. Our ongoing experiments suggest that this is a Gas-coupled receptor, suggesting that signaling mediated by this receptor “tunes” PKA-dependent basal Gli3R-processing.
We plan to implement chemical library-based approaches and biochemical purification strategies from embryo/brain lysates in order to discover the endogenous ligand for this receptor. A recent study on chemical modifiers of Chlamydomnas flagella has detected a set of compounds that act on class A GPCRs, and provides us potential candidates for deorphaning this receptor (Avasthi et al., 2012).
We would utilize the excellent high-throughput screening facilities in UTSW for these purposes. Besides, complementation assays in the Gpr161 knockout fibroblasts using signaling-competent non-ciliary or non-internalizing versions of the receptor would help us address the important question of the relevance of the cilium as a regulatable signaling compartment in the function of this GPCR.
Avasthi, P., Marley, A., Lin, H., Gregori-Puigjane, E., Schoichet, B.K., Von Zastrow, M., and Marshall, W.F. (2012). "A chemical screen identifies class A G-protein coupled receptors as regulators of cilia." ACS Chem Biol.