Optogenetic Toolkit for Remote Control of Voltage-Gated Calcium Channels
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Project Summary/:Owing to the successful use of engineered microbial opsins to remotely control neuronal excitability at highspatiotemporal resolution, considerable new insights into the causal relationship between circuit activity andneuropsychiatric diseases have been obtained through optogenetic approaches. Existing optogenetic tools areprimarily designed to manipulate the flow of ions, such as sodium, potassium and chloride, that support anelectrogenic role in the brain of mammals. By contrast, calcium ion passing through voltage gated calcium(CaV) channels not only alters membrane potential but also functions as an indispensable messenger toregulate neuronal gene expression, synaptic transmission, neurite outgrowth and memory formation. CaVchannels are also essential for cardiac and smooth contractility. CaV channels serve as emerging andattractive therapeutic targets for neuropsychiatric and cardiovascular diseases. However, noninvasive tools todirectly and selectively photo-modulate the flow of calcium ion in neurons and cardiomyocytes are still limited.Another technical roadblock that faces the current in vivo optogenetics and optical neuromodulation is theinability of most existing tools to stimulate deep and wide within the brain without the use of invasive indwellingfiber optic probes. To tackle these two technical challenges, we propose to optically inhibit CaV channel activityby engineering light sensitivities into key CaV negative regulators, and in parallel, to develop bio-compatiblenano-antennae-upconversion nanoparticles (UCNPs) as a â€œcordlessâ€ optogenetic platform to capture andconvert low power, tissue-penetrant, near infrared radiation (NIR) into blue light. This nanoantenna will act as alight-delivery transducer to modulate voltage-gated calcium channels, as well as calcium-dependent activitiesin excitable tissues, with precise spatiotemporal control. We propose two specific aims to advance our platformto excitable cells by using neuronal cells as proof-of-concept. In Aim 1, we will develop new optogenetic toolsto photo-control CaV channel function, and characterize the capacity of our first-generation UCNPs to act asâ€œnanoantennaâ€. In Aim 2, we will develop next generation UCNPs with high photoconversion efficiencies andenhanced biocompatibility. We anticipate that our NIR light-stimulable optogenetic platform will enable remoteand noninvasive control of cell activities in excitable tissues, and permit modulation of their intricate inter-cellular interactions under both physiological and pathological conditions at large scale. Given the widedistribution and close involvement of CaV channels in multiple diseases, the techniques and tools that wedevelop can be broadly extended to interrogate other types of tissues across multiple systems. In summary,the proposed early-stage, cordless optogenetic technology is anticipated to overcome many of the limitationsof current fiber optics-based optogenetic approaches, and will enable new and broad applications in bothbiomedical research and human health.