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Investigating neuronal function with optically controllable proteins.

Zhou XX, Pan M, Lin MZ - Front Mol Neurosci (2015)

Bottom Line: For example, neurite extension and synaptogenesis both involve localized and transient activation of cytoskeletal and signaling proteins, allowing changes in microarchitecture to occur rapidly and in a localized manner.These tools have demonstrated versatility in controlling various proteins and thereby cellular functions, and possess enormous potential for future applications in nervous systems.Just as optogenetic control of neuronal firing using opsins has changed how we investigate the function of cellular circuits in vivo, optical control may yet yield another revolution in how we study the circuitry of intracellular signaling in the brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Stanford University Stanford, CA, USA.

ABSTRACT
In the nervous system, protein activities are highly regulated in space and time. This regulation allows for fine modulation of neuronal structure and function during development and adaptive responses. For example, neurite extension and synaptogenesis both involve localized and transient activation of cytoskeletal and signaling proteins, allowing changes in microarchitecture to occur rapidly and in a localized manner. To investigate the role of specific protein regulation events in these processes, methods to optically control the activity of specific proteins have been developed. In this review, we focus on how photosensory domains enable optical control over protein activity and have been used in neuroscience applications. These tools have demonstrated versatility in controlling various proteins and thereby cellular functions, and possess enormous potential for future applications in nervous systems. Just as optogenetic control of neuronal firing using opsins has changed how we investigate the function of cellular circuits in vivo, optical control may yet yield another revolution in how we study the circuitry of intracellular signaling in the brain.

No MeSH data available.


Related in: MedlinePlus

Other photosensory modules with potential benefits for neurobiological applications.(A) Phytochrome – PIF based protein membrane translocation. Phytochrome (PhyB) is localized at plasma membrane by fusing to a membrane-trafficking peptide, and a POI is in fusion with the PIF domain. Red light-mediated PhyB-PIF interaction drives the POI to the plasma membrane, initiating downstream reactions. (B) Dronpa system for optogenetic control of protein function through steric blockade. Dronpa(K145N) forms tetramers. A POI is flanked by Dronpa on either terminus. When Dronpa is in multimeric form, the protein is caged and unable to perform its normal functions. Exposure to cyan light causes Dronpa to monomerize, uncaging the protein. A subsequent exposure to violet light will cause Dronpa to multimerize, again caging the protein.
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Figure 7: Other photosensory modules with potential benefits for neurobiological applications.(A) Phytochrome – PIF based protein membrane translocation. Phytochrome (PhyB) is localized at plasma membrane by fusing to a membrane-trafficking peptide, and a POI is in fusion with the PIF domain. Red light-mediated PhyB-PIF interaction drives the POI to the plasma membrane, initiating downstream reactions. (B) Dronpa system for optogenetic control of protein function through steric blockade. Dronpa(K145N) forms tetramers. A POI is flanked by Dronpa on either terminus. When Dronpa is in multimeric form, the protein is caged and unable to perform its normal functions. Exposure to cyan light causes Dronpa to monomerize, uncaging the protein. A subsequent exposure to violet light will cause Dronpa to multimerize, again caging the protein.

Mentions: Other than opsins, all the photosensory domains discussed so far use either flavin compounds or tryptophan residues as chromophores, necessitating the use of blue or UV light. This may be problematic for illuminating large regions of the brain or for prolonged stimulation, as these wavelengths of light are less penetrating and more phototoxic than redder wavelengths. Indeed, the presence of FMN and FAD in essential cellular enzymes, the reason for their ubiquity in all kingdoms of life, is also the cause of blue light-mediated phototoxicity, and UV light is efficiently absorbed by protein and DNA. However, other photosensory domains exist that use redder wavelengths of light, and these have the potential to allow multichromatic control of a variety of biological events in neurons, or optical control with less phototoxicity. Phytochromes are a family of red-absorbing photoreceptors found in plants, fungi and bacteria that use tetrapyrrole cofactors as chromophores. Plant phytochromes bind to phytochrome interaction factors (PIFs) in response to light (Li et al., 2011). This interaction was used for light control of transcription and protein localization in yeast (Shimizu-Sato et al., 2002; Yang et al., 2013) and membrane trafficking of signaling proteins in mammalian cells (Levskaya et al., 2009; Toettcher et al., 2013; Figure 7A). The phytochromobilin cofactor used by plant phytochromes is not present in yeast and animal cells but can be added to cell culture. Recently, expression of the synthetic enzymes for phytochromobilin in mammalian cells was found to produce enough phytochromobilin for phytochrome maturation (Muller et al., 2013), suggesting that plant phytochromes could be usable in mice as well. Alternatively, phytochromes that use biliverdin, a natural degradation product of heme, may be adaptable to control mammalian proteins. A fusion of a biliverdin-utilizing bacterial phytochrome to a phosphodiesterase was recently shown to allow light control of cAMP levels in mammalian cells and zebrafish embryos (Gasser et al., 2014). However, light-dependent binding partners of biliverdin-utilizing phytochromes have not yet been described. The unique red absorption characteristic of phytochromes enables its usage in combination with a violet- or blue-absorbing light activated system, so that two or three processes can be controlled concurrently, potentially allowing roles of multiple proteins in complex cell signaling pathways to be disentangled (Muller et al., 2014).


Investigating neuronal function with optically controllable proteins.

Zhou XX, Pan M, Lin MZ - Front Mol Neurosci (2015)

Other photosensory modules with potential benefits for neurobiological applications.(A) Phytochrome – PIF based protein membrane translocation. Phytochrome (PhyB) is localized at plasma membrane by fusing to a membrane-trafficking peptide, and a POI is in fusion with the PIF domain. Red light-mediated PhyB-PIF interaction drives the POI to the plasma membrane, initiating downstream reactions. (B) Dronpa system for optogenetic control of protein function through steric blockade. Dronpa(K145N) forms tetramers. A POI is flanked by Dronpa on either terminus. When Dronpa is in multimeric form, the protein is caged and unable to perform its normal functions. Exposure to cyan light causes Dronpa to monomerize, uncaging the protein. A subsequent exposure to violet light will cause Dronpa to multimerize, again caging the protein.
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Figure 7: Other photosensory modules with potential benefits for neurobiological applications.(A) Phytochrome – PIF based protein membrane translocation. Phytochrome (PhyB) is localized at plasma membrane by fusing to a membrane-trafficking peptide, and a POI is in fusion with the PIF domain. Red light-mediated PhyB-PIF interaction drives the POI to the plasma membrane, initiating downstream reactions. (B) Dronpa system for optogenetic control of protein function through steric blockade. Dronpa(K145N) forms tetramers. A POI is flanked by Dronpa on either terminus. When Dronpa is in multimeric form, the protein is caged and unable to perform its normal functions. Exposure to cyan light causes Dronpa to monomerize, uncaging the protein. A subsequent exposure to violet light will cause Dronpa to multimerize, again caging the protein.
Mentions: Other than opsins, all the photosensory domains discussed so far use either flavin compounds or tryptophan residues as chromophores, necessitating the use of blue or UV light. This may be problematic for illuminating large regions of the brain or for prolonged stimulation, as these wavelengths of light are less penetrating and more phototoxic than redder wavelengths. Indeed, the presence of FMN and FAD in essential cellular enzymes, the reason for their ubiquity in all kingdoms of life, is also the cause of blue light-mediated phototoxicity, and UV light is efficiently absorbed by protein and DNA. However, other photosensory domains exist that use redder wavelengths of light, and these have the potential to allow multichromatic control of a variety of biological events in neurons, or optical control with less phototoxicity. Phytochromes are a family of red-absorbing photoreceptors found in plants, fungi and bacteria that use tetrapyrrole cofactors as chromophores. Plant phytochromes bind to phytochrome interaction factors (PIFs) in response to light (Li et al., 2011). This interaction was used for light control of transcription and protein localization in yeast (Shimizu-Sato et al., 2002; Yang et al., 2013) and membrane trafficking of signaling proteins in mammalian cells (Levskaya et al., 2009; Toettcher et al., 2013; Figure 7A). The phytochromobilin cofactor used by plant phytochromes is not present in yeast and animal cells but can be added to cell culture. Recently, expression of the synthetic enzymes for phytochromobilin in mammalian cells was found to produce enough phytochromobilin for phytochrome maturation (Muller et al., 2013), suggesting that plant phytochromes could be usable in mice as well. Alternatively, phytochromes that use biliverdin, a natural degradation product of heme, may be adaptable to control mammalian proteins. A fusion of a biliverdin-utilizing bacterial phytochrome to a phosphodiesterase was recently shown to allow light control of cAMP levels in mammalian cells and zebrafish embryos (Gasser et al., 2014). However, light-dependent binding partners of biliverdin-utilizing phytochromes have not yet been described. The unique red absorption characteristic of phytochromes enables its usage in combination with a violet- or blue-absorbing light activated system, so that two or three processes can be controlled concurrently, potentially allowing roles of multiple proteins in complex cell signaling pathways to be disentangled (Muller et al., 2014).

Bottom Line: For example, neurite extension and synaptogenesis both involve localized and transient activation of cytoskeletal and signaling proteins, allowing changes in microarchitecture to occur rapidly and in a localized manner.These tools have demonstrated versatility in controlling various proteins and thereby cellular functions, and possess enormous potential for future applications in nervous systems.Just as optogenetic control of neuronal firing using opsins has changed how we investigate the function of cellular circuits in vivo, optical control may yet yield another revolution in how we study the circuitry of intracellular signaling in the brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Stanford University Stanford, CA, USA.

ABSTRACT
In the nervous system, protein activities are highly regulated in space and time. This regulation allows for fine modulation of neuronal structure and function during development and adaptive responses. For example, neurite extension and synaptogenesis both involve localized and transient activation of cytoskeletal and signaling proteins, allowing changes in microarchitecture to occur rapidly and in a localized manner. To investigate the role of specific protein regulation events in these processes, methods to optically control the activity of specific proteins have been developed. In this review, we focus on how photosensory domains enable optical control over protein activity and have been used in neuroscience applications. These tools have demonstrated versatility in controlling various proteins and thereby cellular functions, and possess enormous potential for future applications in nervous systems. Just as optogenetic control of neuronal firing using opsins has changed how we investigate the function of cellular circuits in vivo, optical control may yet yield another revolution in how we study the circuitry of intracellular signaling in the brain.

No MeSH data available.


Related in: MedlinePlus