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. 2023 May 11;12:e85041. doi: 10.7554/eLife.85041

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© 2023, Sorkaç et al

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

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Figure 1. — (A) The components of retro-Tango. (B) In retro-Tango, all neurons express two of the components of the signaling cascade: human glucagon receptor::TEV cleavage site::QF and human β-arrestin2::TEV protease. They also carry the gene encoding the presynaptic mtdTomato reporter (magenta) under the control of QF. Therefore, all neurons are capable of expressing the reporter. In starter neurons expressing Gal4, the ligand (human glucagon::mouse ICAM5) is expressed along with the GFP reporter (cyan) marking the postsynaptic starter neurons. The mICAM5 fusion localizes the ligand to the postsynaptic sites such that the ligand activates its receptor only across the synapse. Upon activation of the receptor in the presynaptic neuron, the Arrestin-TEV fusion is recruited. TEV-mediated proteolytic cleavage then releases the transcription factor QF from the receptor. QF in turn translocates to the nucleus and initiates transcription of the presynaptic magenta reporter. In neurons that are not presynaptic to the starter neurons, the reporter is not expressed. (C) In the absence of a Gal4 driver, the ligand is not expressed, and the signaling cascade is not triggered, resulting in no expression of the reporters.

Figure 1—figure supplement 1. — (A) The components of retro-Tango. (B) In retro-Tango, all neurons express two of the components of the signaling cascade: human glucagon receptor::TEV cleavage site::QF and human β-arrestin2::TEV protease. They also carry the gene encoding the presynaptic mtdTomato reporter (magenta) under the control of QF. Therefore, all neurons are capable of expressing the reporter. In starter neurons expressing Gal4, the ligand (human glucagon::mouse ICAM5) is expressed along with the GFP reporter (cyan) marking the postsynaptic starter neurons. The mICAM5 fusion localizes the ligand to the postsynaptic sites such that the ligand activates its receptor only across the synapse. Upon activation of the receptor in the presynaptic neuron, the Arrestin-TEV fusion is recruited. TEV-mediated proteolytic cleavage then releases the transcription factor QF from the receptor. QF in turn translocates to the nucleus and initiates transcription of the presynaptic magenta reporter. In neurons that are not presynaptic to the starter neurons, the reporter is not expressed. (C) In the absence of a Gal4 driver, the ligand is not expressed, and the signaling cascade is not triggered, resulting in no expression of the reporters.