Optophysiology: Illuminating cell physiology with optogenetics

Abstract

Optogenetics combines light and genetics to enable precise control of living cells, tissues, and organisms with tailored functions. Optogenetics has the advantages of noninvasiveness, rapid responsiveness, tunable reversibility, and superior spatiotemporal resolution. Following the initial discovery of microbial opsins as light-actuated ion channels, a plethora of naturally occurring or engineered photoreceptors or photosensitive domains that respond to light at varying wavelengths has ushered in the next chapter of optogenetics. Through protein engineering and synthetic biology approaches, genetically-encoded photoswitches can be modularly engineered into protein scaffolds or host cells to control a myriad of biological processes, as well as to enable behavioral control and disease intervention in vivo. Here, we summarize these optogenetic tools on the basis of their fundamental photochemical properties to better inform the chemical basis and design principles. We also highlight exemplary applications of opsin-free optogenetics in dissecting cellular physiology (designated "optophysiology"), and describe the current progress, as well as future trends, in wireless optogenetics, which enables remote interrogation of physiological processes with minimal invasiveness. This review is anticipated to spark novel thoughts on engineering next-generation optogenetic tools and devices that promise to accelerate both basic and translational studies.

Rhodopsins: An Excitingly Versatile Protein Species for Research, Development and Creative Engineering

“…This would undoubtedly be accompanied by further physiological expansion of optogenetic tools. A wider spectral range of neuronal activity modulators and voltage sensors together with improved optics will increase the scope for (all)-optical electrophysiological characterization of neural circuitry, also lending insight into neuronal function (and dysfunction) in the brain ( Villette et al, 2019 ; Guimarães Backhaus et al, 2021 ; Sharma et al, 2021 ; Zou et al, 2021 ; Prakash et al, 2022 ; Sridharan et al, 2022 ; Tan et al, 2022 ). Other important medical targets may also arise using optogenetics to correct physiological defects and address pathological conditions, where first steps have already been taken ( Braun et al, 1995 ; Deubner et al, 2019 ; Shen et al, 2020 ; Acharya et al, 2021 ; Cokic et al, 2021 ; Kathe et al, 2021 ; Gilhooley et al, 2022 ; Sun et al, 2022 ).…”

Isorhodopsin: An Undervalued Visual Pigment Analog

“…Eventually, in silico ab initio structural model building exploiting the newly available algorithms [288][289][290] will allow rapid testing of the chromophoric potential of theoretical promising retinal analogs for (iso)rhodopsins [291]. Atomic insight into the photoisomerization trajectories of isorhodopsins will be of utmost importance, not only from a photochemical point of view, but also for the design of retinal proteins with selected properties-both for bioengineering purposes and in optogenetics [292,293].…”

LITOS: a versatile LED illumination tool for optogenetic stimulation

“…While optogenetics was first used in neurobiology 1 , it is now widely used to control a wide variety of cell-biological processes with high spatio-temporal resolution 2 . This has been made possible by the discovery of a number of light-responsive protein domains that were engineered to build actuators to control almost any cell-biological process 2 . The precision of optogenetics to perturb cellular systems can lead to a deeper understanding of their dynamic regulation 3 .…”