An optonanobody for reversible photoactivation of recombinant and native α7 nicotinic
Photopharmacology which enables the precise optical control of endogenous receptor activity, represents a powerful approach in neuroscience. However, photochromic diffusible ligands often exhibit limited subtype specificity, while alternative strategies for controlling specific receptor subtypes require genetic modification. Here, to achieve high subtype selectivity without the need of receptor engineering, we introduce a genetically independent strategy for optical control of endogenous receptors based on highly selective and chemically-defined photoswitchable nanobodies. By covalently coupling a light-sensitive azobenzene agonist to a high-affinity nanobody targeting 7 nicotinic acetylcholine receptor (nAChR), we engineered MalAzoCh-C4, an optonanobody that confers reversible, light-dependent activation of native 7 receptors. In Xenopus oocytes, MalAzoCh-C4 enables wavelength-controlled modulation of recombinant 7 receptors, with enhanced activity in trans configuration. In acute hippocampal slices, application of MalAzoCh-C4 produces robust photocontrol of endogenous 7 nAChRs in interneurons, sufficient to modulate action potential firing. This strategy combines nanobody specificity with the temporal resolution of photopharmacology, establishing optonanobodies as a platform for control of native neuronal receptors.