CaMello-XR enables visualization and optogenetic control of G(q/11) signals and receptor trafficking in GPCR-specific domains

The signal specificity of G protein-coupled receptors (GPCRs) including serotonin receptors (5-HT-R) depends on the trafficking and localization of the GPCR within its subcellular signaling domain. Visualizing traffic-dependent GPCR signals in neurons is difficult, but important to understand the contribution of GPCRs to synaptic plasticity. We engineered CaMello (Ca(2+)-melanopsin-local-sensor) and CaMello-5HT(2A) for visualization of traffic-dependent Ca(2+) signals in 5-HT(2A)-R domains. These constructs consist of the light-activated G(q/11) coupled melanopsin, mCherry and GCaMP6m for visualization of Ca(2+) signals and receptor trafficking, and the 5-HT(2A) C-terminus for targeting into 5-HT(2A)-R domains. We show that the specific localization of the GPCR to its receptor domain drastically alters the dynamics and localization of the intracellular Ca(2+) signals in different neuronal populations in vitro and in vivo. The CaMello method may be extended to every GPCR coupling to the G(q/11) pathway to help unravel new receptor-specific functions in respect to synaptic plasticity and GPCR localization.