Technology Review Cellscience Reviews Vol 3 No 4 ISSN 1742-8130

Light Tools for neuroscience: Channelrhodopsin and light-activated enzymes

Channelrhodopsins from green algae are a class of rhodopsins which possess an intrinsic conductance for H⁺ as well as for other mono- and divalent cations. Their conductance is gated by light absorption, and the isomerization of the retinal chromophore functions as the switch. Channelrhodopsins were first characterized in Xenopus oocytes but since 2005 have been widely employed in neurobiology. ChR-GFP chimera constructs have been expressed in a wide variety of neuronal cells and tissues, including Caenorhabditis Elegans, chicken embryos, Drosophila and mice, all simply to endow the rapid and spatially precise control of action potentials. Here the properties of channelrhodopsins are summarized in order to provide further perspective for their potential application throughout neuroscience and medical research. Beyond this we suggest possible applications for other classes of light-activated enzymes, such as the photo-activated cyclase (PAC) from the flagellate Euglena, which also show great promise as tools for neuroscience research.

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