Genetically Targeted Optical Control of an Endogenous G Protein-Coupled Receptor

Abstract

G protein-coupled receptors (GPCRs) are membrane proteins that play important roles in biology. However, our understanding of their function in complex living systems is limited because we lack tools that can target individual receptors with sufficient precision. State-of-the-art approaches, including DREADDs, optoXRs, and PORTL gated-receptors, control GPCR signaling with molecular, cell type, and temporal specificity. Nonetheless, these tools are based on engineered non-native proteins that may (i) express at nonphysiological levels, (ii) localize and turnover incorrectly, and/or (iii) fail to interact with endogenous partners. Alternatively, membrane-*

Two-Photon Excitation of Azobenzene Photoswitches for Synthetic Optogenetics

“…Another scheme to bypass protein modification is by attaching the photoswitch next to its intended target. This may include expression of membrane anchors (e.g., a transmembrane domain with the tether facing the extracellular) to conjugate the photoswitch which can then modulate adjacent endogenous proteins [29]. Cumulative plot of number of publications across years was performed by searching for specific terms (chemical-optogenetics, photopharmacology, optopharmacology, synthetic optogenetics, optogenetic pharmacology, photoswitch, azobenzene and photo), as well as by searching for publications from recognized researchers in the field (e.g., Erlanger BF, Poolman B, Feringa B, Lester HA, Trauner D, Kramer RH, Isacoff EY, Woolley GA, Gorostiza P, Paoletti P, Ellis-Davies GCR, etc.).…”

Optogenetic Modulation for the Treatment of Traumatic Brain Injury

“…Photoswitchable Orthogonal Remotely Tethered Ligands (PORTLs) are utilized in another photopharmacological approach. PORTLs contain a receptor ligand, namely glutamate, which photoisomerizes following exposure to specific wavelengths of light, thus permitting photoactivation of mGluRs [115]. As mGluRs have been implicated in cellular processes following TBI, such as mechanisms that attenuate neuronal cell death, the receptors are a potential target for treatment [116,117].…”

“…However, these approaches require significant alteration of the receptor sequence. This may result in receptors that are unable to bind to their endogenous ligands, making their physiological roles obsolete [115]. Newer methods have been developed to target endogenous receptors, therefore circumventing limitations associated to receptor sequence modification.…”

“…Newer methods have been developed to target endogenous receptors, therefore circumventing limitations associated to receptor sequence modification. Drug Affinity Responsive Target Stability technology, which provides membrane-anchored ligands that target endogenous receptors, has recently been combined with PORTLs to permit genetically specified and reversible GPCR activation [115]. Although further investigation is required to assess the efficacy of such technology for TBI treatment in both animal and human models, these methods represent potential alternatives that offer advantages over current treatment modalities.…”

Transformation of Receptor Tyrosine Kinases into Glutamate Receptors and Photoreceptors

“…Initial attempts to convert VKRs themselves into photoreceptors had been unsuccessful. Since our PORTL approach to the optical control of mGluR2 worked well [16,21,24] and since the downstream effects of hIR and hMET were much better understood than those of VKRs, we ultimately settled on a more audacious approach merging two receptors involved in very different signal transduction pathways. Our results confirm that the recombination of modules from vastly different families can lead to functional transmembrane receptors with interesting functional properties.…”