Curated Optogenetic Publication Database

Abstract: Dendritic spines are the primary sites of excitatory synaptic transmission in the vertebrate brain, and the morphology of these actin-rich structures correlates with synaptic function. Here we demonstrate a unique method for inducing spine enlargement and synaptic potentiation in dispersed hippocampal neurons, and use this technique to identify a coordinator of these processes; Ras-specific guanine nucleotide releasing factor 2 (RasGRF2). RasGRF2 is a dual Ras/Rac guanine nucleotide exchange factor (GEF) that is known to be necessary for long-term potentiation in situ. Contrary to the prevailing assumption, we find RasGRF2's Rac-GEF activity to be essential for synaptic potentiation by using a molecular replacement strategy designed to dissociate Rac- from Ras-GEF activities. Furthermore, we demonstrate that Rac1 activity itself is sufficient to rapidly modulate postsynaptic strength by using a photoactivatable derivative of this small GTPase. Because Rac1 is a major actin regulator, our results support a model where the initial phase of long-term potentiation is driven by the cytoskeleton.

Abstract: Optogenetic techniques provide effective ways of manipulating the functions of selected neurons with light. In the current study, we engineered an optogenetic technique that directly inhibits neurotransmitter release. We used a genetically encoded singlet oxygen generator, miniSOG, to conduct chromophore assisted light inactivation (CALI) of synaptic proteins. Fusions of miniSOG to VAMP2 and synaptophysin enabled disruption of presynaptic vesicular release upon illumination with blue light. In cultured neurons and hippocampal organotypic slices, synaptic release was reduced up to 100%. Such inhibition lasted >1 hr and had minimal effects on membrane electrical properties. When miniSOG-VAMP2 was expressed panneuronally in Caenorhabditis elegans, movement of the worms was reduced after illumination, and paralysis was often observed. The movement of the worms recovered overnight. We name this technique Inhibition of Synapses with CALI (InSynC). InSynC is a powerful way to silence genetically specified synapses with light in a spatially and temporally precise manner.

Abstract: Optical control of protein interactions has emerged as a powerful experimental paradigm for manipulating and studying various cellular processes. Tools are now available for controlling a number of cellular functions, but some fundamental processes, such as protein secretion, have been difficult to engineer using current optical tools. Here we use UVR8, a plant photoreceptor protein that forms photolabile homodimers, to engineer the first light-triggered protein secretion system. UVR8 fusion proteins were conditionally sequestered in the endoplasmic reticulum, and a brief pulse of light triggered robust forward trafficking through the secretory pathway to the plasma membrane. UVR8 was not responsive to excitation light used to image cyan, green, or red fluorescent protein variants, allowing multicolor visualization of cellular markers and secreted protein cargo as it traverses the cellular secretory pathway. We implemented this novel tool in neurons to demonstrate restricted, local trafficking of secretory cargo near dendritic branch points.

Abstract: The recent success of channelrhodopsin in optogenetics has also caused increasing interest in enzymes that are directly activated by light. We have identified in the genome of the bacterium Beggiatoa a DNA sequence encoding an adenylyl cyclase directly linked to a BLUF (blue light receptor using FAD) type light sensor domain. In Escherichia coli and Xenopus oocytes, this photoactivated adenylyl cyclase (bPAC) showed cyclase activity that is low in darkness but increased 300-fold in the light. This enzymatic activity decays thermally within 20 s in parallel with the red-shifted BLUF photointermediate. bPAC is well expressed in pyramidal neurons and, in combination with cyclic nucleotide gated channels, causes efficient light-induced depolarization. In the Drosophila central nervous system, bPAC mediates light-dependent cAMP increase and behavioral changes in freely moving animals. bPAC seems a perfect optogenetic tool for light modulation of cAMP in neuronal cells and tissues and for studying cAMP-dependent processes in live animals.