Optogenetic Tools for Subcellular Applications in Neuroscience

Abstract

The ability to study cellular physiology using photosensitive, genetically encoded molecules has profoundly transformed neuroscience. The modern optogenetic toolbox includes fluorescent sensors to visualize signaling events in living cells and optogenetic actuators enabling manipulation of numerous cellular activities. Most optogenetic tools are not targeted to specific subcellular compartments but are localized with limited discrimination throughout the cell. Therefore, optogenetic activation often does not reflect context-dependent effects of highly localized intracellular signaling events. Subcellular targeting is required to achieve more specific optogenetic readouts and photomanipulation. Here we first provide a detailed overview of the available optogenetic tools with a focus on optogenetic actuators. Second, we review established strategies for targeting these tools to specific subcellular compartments. Finally, we discuss useful tools and targeting strategies that are currently missing from the optogenetics repertoire and provide suggestions for novel subcellular optogenetic applications.

Manipulating midbrain dopamine neurons and reward-related behaviors with light-controllable nicotinic acetylcholine receptors

“…The photochemical properties of the azobenzene photoswitch make this strategy ideally suited for reversibly controlling neurotransmitter receptors with high efficacy and at speeds that rival synaptic transmission (Lemoine et al, 2013; Levitz et al, 2013; Lin et al, 2015; Szobota et al, 2007). Comparatively, strategies for photosensitizing proteins based on the fusion of light-sensitive modules (Rost et al, 2017) or chromophore-assisted light-inactivation (Lin et al, 2013; Takemoto et al, 2017) are too slow or irreversible, respectively. Due to the constrains of bioconjugation, in vivo use of photoswitch-tethered receptors in mice has been restricted to the eye (Gaub et al, 2014) and to superficial layers of the cerebral cortex (Levitz et al, 2016; Lin et al, 2015).…”

Optical and thermal simulations for the design of optodes for minimally invasive optogenetics stimulation or photomodulation of deep and large cortical areas in non-human primate brain

“…, C photons is the number of photons per mm 3 , c is the speed of light in vacuum in mm.s −1 , n is the media optical index, i.e. 1.4 for biological tissues, and E photon is the energy of a photon at 674 nm.…”

“…Simple pulses of light delivered through optical fibers can trigger or inhibit neuronal activity within milliseconds [1]. Since its first implementation in the 2000s the technique has been used to explore neuronal connectivity over large scales in many fields such as cognitive, behavioral and learning neuroscience [2][3][4][5]. It has evolved quickly with a systematic screening of light activated proteins and the mutagenesis of existing opsins.…”

Optical Regulation of Class C GPCRs by Photoswitchable Orthogonal Remotely Tethered Ligands

“…An alternative to DREADDs that allows both genetic targeting and optical control has been to use intrinsically light-sensitive GPCRs from the opsin family, including rhodopsin and melanopsin [8, 15]. Similar to DREADDs, exogenous expression of opsins, which are typically not expressed outside of the retina, allows general G protein pathways to be manipulated but does not facilitate the study of specific GPCRs.…”