Robust photoregulation of GABAA receptors by allosteric modulation with a propofol analogue

Abstract

Photochemical switches represent a powerful method for improving pharmacological therapies and controlling cellular physiology. Here we report the photo-regulation of GABAA receptors (GABAARs) by a derivative of propofol (2,6-diisopropylphenol), a GABAAR allosteric modulator, that we have modified to contain photo-isomerizable azobenzene. Using α1β2γ2 GABAARs expressed in Xenopus laevis oocytes and native GABAARs of isolated retinal ganglion cells, we show that the trans-azobenzene isomer of the new compound (trans-MPC088), generated by visible light (wavelengths ~440 nm), potentiates the GABA-elicited response and at higher concentrations directly activates the receptors. cis-MPC088, generated from trans-MPC088 by UV light (~365 nm), produces little if any receptor potentiation/activation. In cerebellar slices, MPC088 co-applied with GABA affords bidirectional photo-modulation of Purkinje cell membrane current and spike-firing rate. The findings demonstrate photo-control of GABAARs by an allosteric ligand and open new avenues for fundamental and clinically oriented research on GABAARs, a major class of neurotransmitter receptors in the central nervous system.

Optogenetic Approaches to Restoring Vision

“…Currently, azobenzenes have been the choice for the photoisomerizable group (Broichhagen & Trauner 2014). Optopharmacological photoswitches have been developed to regulate membrane channels (Polosukhina et al 2012, Tochitsky et al 2014) and ligand-gated receptors such as GABA receptors (Yue et al 2012) and glutamate receptors (Adesnik et al 2005, Volgraf et al 2007). The optopharmacological photoswitches can also be covalently attached to genetically modified proteins, channels, or receptors.…”

Optical control of an ion channel gate

“…Of special interest is the optogenetic pharmacology (also known as optochemical genetic) (3,4), which allows the control of an ion channel or receptor function by a photoswitchable ligand that is irreversibly tethered to the genetically modified protein through cysteine substitution (3,4). Ligands are pharmacologically active substances targeting either competitive (5-7), or noncompetitive binding sites (8)(9)(10), and light sensitivity is mostly conferred by substituting a photoisomerizable azobenzene derivative, which interconverts reversibly between a long trans-isomer and a short cis-isomer (11). However, this approach is technically demanding, as it requires the design of site-specific ligands for each target.…”

Optogenetics: Perspectives in Biomedical Research (Review)

“…By comparing the agonist-induced conductance with the cis/trans ratio, Lester et al [42] provided compelling evidences of the rapid conformational transitions of nAChR channels during activation. More recent designs are represented by photochromic ligands of ionotropic receptors for glutamate [25] or GABA [43,44]. In the first design, the natural ligand, glutamate, is coupled to azobenzene (Figure 3 (b)), while for photochromic ligand of GABA, the aromatic group of the ligand propofol is added.…”