Anion-conducting channelrhodopsin explained

Anion-conducting channelrhodopsins are light-gated ion channels that open in response to light and let negatively charged ions (such as chloride) enter a cell. All channelrhodopsins use retinal as light-sensitive pigment, but they differ in their ion selectivity. Anion-conducting channelrhodopsins are used as tools to manipulate brain activity in mice, fruit flies and other model organisms (Optogenetics). Neurons expressing anion-conducting channelrhodopsins are silenced when illuminated with light, an effect that has been used to investigate information processing in the brain. For example, suppressing dendritic calcium spikes in specific neurons with light reduced the ability of mice to perceive a light touch to a whisker.[1] Studying how the behavior of an animal changes when specific neurons are silenced allows scientists to determine the role of these neurons in the complex circuits controlling behavior.

The first anion-conducting channelrhodopsins were engineered from the cation-conducting light-gated channel Channelrhodopsin-2 by removing negatively charged amino acids from the channel pore (Fig. 1).[2] As the main anion of extracellular fluid is chloride (Cl−), anion-conducting channelrhodopsins are also known as “chloride-conducting channelrhodopsins” (ChloCs). Naturally occurring anion-conducting channelrhodopsins (ACRs) were subsequently identified in cryptophyte algae. The crystal structure of the natural GtACR1 has recently been solved, paving the way for further protein engineering.[3] [4]

Variants

namespecies of originabsorptionreferenceproperties, applications
slowChloCChlamydomonas reinhardtiiblueWietek et al. 2014first generation, mixed conductance
iC1C2Chlamydomonas reinhardtiiblueBerndt et al. 2014[5] first generation, mixed conductance
iChloCChlamydomonas reinhardtiiblueWietek et al. 2015[6] inhibition of perception in mice
iC++Chlamydomonas reinhardtiiblueBerndt et al. 2016[7] inhibition of sleep in mice[8]
GtACR1Guillardia thetagreenGovorunova et al. 2015[9] inhibition of behavior in Drosophila[10] [11] inhibition of rat heart muscle cells[12] holographic spike suppression in mouse cortex[13]
GtACR1(C102A)Guillardia thetagreen on Govorunova et al. 2018bistable
GtACR1(R83Q/N239Q) FLASHGuillardia thetagreen on Kato et al. 2018very fast closing, large currentsinhibition of swimming in C. elegans, inhibition of spiking in mouse
GtACR2Guillardia thetablueGovorunova et al. 2015inhibition of behavior in Drosophila inhibition of fear extinction in mice[14]
PsACR1Proteomonas sulcatagreenWietek et al. 2016,[15] Govorunova et al. 2016[16] large currents
ZipACRProteomonas sulcatagreenGovorunova et al. 2017[17] very fast
RapACRRhodomonas salinagreenGovorunova et al. 2018[18] very fast, large currents
SwiChR++Chlamydomonas reinhardtii blue on Berndt et al. 2016bistable
Phobos CAChlamydomonas reinhardtiiblue onWietek et al. 2017[19] bistable
AuroraChlamydomonas reinhardtiiorange-redWietek et al. 2017stop locomotion of Drosophila larvae
MerMAIDsunknowngreenOppermann et al. 2019[20] rapidly inactivating

Applications

Anion-conducting channelrhodopsins (ACRs) have been used as optogenetic tools to inhibit neuronal activation. When expressed in nerve cells, ACRs act as light-gated chloride channels. Their effect on the activity of the neuron is comparable to GABAA receptors, ligand-gated chloride channels found in inhibitory synapses: As the chloride concentration in mature neurons is very low, illumination results in an inward flux of negatively charged ions, clamping the neuron at the chloride reversal potential (- 65 mV). Under these conditions, excitatory synaptic inputs are not able to efficiently depolarize the neuron. This effect is known as shunting inhibition (as opposed to inhibition by hyperpolarization). Illuminating the dendrite prevents the generation of dendritic calcium spikes while illumination of the entire neuron blocks action potential initiation in response to sensory stimulation. Axon terminals, however, have a higher chloride concentration and are therefore excited by ACRs.[21] To inhibit neurons with wide-field illumination, it has proven useful to restrict ACRs to the somatic compartment (ST variants).

Due to their high light sensitivity, ACRs can be activated with dim light which does not interfere with visual stimulation, even in very small animals like the fruit fly Drosophila. When combined with a red-light sensitive cation-conducting channelrhodopsin, ACRs allow for bidirectional control of neurons: Silencing with blue light, activation with red light ('Bipoles').[22]

Further reading

Neuron Review (2017): Silencing neurons: Tools, Applications, and Experimental Constraints[23]

Research highlight: A better way to turn off neurons[24]

Perspective: Expanding the optogenetics toolkit[25]

Related: Halorhodopsin, a light-driven chloride pump

Notes and References

  1. Takahashi. Naoya. Oertner. Thomas G.. Hegemann. Peter. Larkum. Matthew E.. 2016-12-23. Active cortical dendrites modulate perception. Science. en. 354. 6319. 1587–1590. 10.1126/science.aah6066. 0036-8075. 28008068. 2016Sci...354.1587T . 28317052.
  2. Wietek. Jonas. Wiegert. J. Simon. Adeishvili. Nona. Schneider. Franziska. Watanabe. Hiroshi. Tsunoda. Satoshi P.. Vogt. Arend. Elstner. Marcus. Oertner. Thomas G.. Hegemann. Peter. 2014-04-25. Conversion of Channelrhodopsin into a Light-Gated Chloride Channel. Science. en. 344. 6182. 409–412. 10.1126/science.1249375. 0036-8075. 24674867. 206554245. free. 2014Sci...344..409W .
  3. Kato. Hideaki E.. Kim. Yoon Seok. Paggi. Joseph M.. Evans. Kathryn E.. Allen. William E.. Richardson. Claire. Inoue. Keiichi. Ito. Shota. Ramakrishnan. Charu. 2018-08-29. Structural mechanisms of selectivity and gating in anion channelrhodopsins. Nature. En. 561. 7723. 349–354. 10.1038/s41586-018-0504-5. 30158697. 0028-0836. 6317992. 2018Natur.561..349K .
  4. Kim. Yoon Seok. Kato. Hideaki E.. Yamashita. Keitaro. Ito. Shota. Inoue. Keiichi. Ramakrishnan. Charu. Fenno. Lief E.. Evans. Kathryn E.. Paggi. Joseph M.. 2018-08-29. Crystal structure of the natural anion-conducting channelrhodopsin GtACR1. Nature. En. 561. 7723. 343–348. 10.1038/s41586-018-0511-6. 30158696. 0028-0836. 6340299. 2018Natur.561..343K .
  5. Berndt. Andre. Lee. Soo Yeun. Ramakrishnan. Charu. Deisseroth. Karl. 2014-04-25. Structure-Guided Transformation of Channelrhodopsin into a Light-Activated Chloride Channel. Science. en. 344. 6182. 420–424. 10.1126/science.1252367. 0036-8075. 24763591. 4096039. 2014Sci...344..420B .
  6. Wietek. Jonas. Beltramo. Riccardo. Scanziani. Massimo. Hegemann. Peter. Oertner. Thomas G.. Wiegert. J. Simon. 2015-10-07. An improved chloride-conducting channelrhodopsin for light-induced inhibition of neuronal activity in vivo. Scientific Reports. en. 5. 10.1038/srep14807. 2045-2322. 14807. 26443033. 4595828. 2015NatSR...514807W .
  7. Berndt. Andre. Lee. Soo Yeun. Wietek. Jonas. Ramakrishnan. Charu. Steinberg. Elizabeth E.. Rashid. Asim J.. Kim. Hoseok. Park. Sungmo. Santoro. Adam. 2016-01-26. Structural foundations of optogenetics: Determinants of channelrhodopsin ion selectivity. Proceedings of the National Academy of Sciences. en. 113. 4. 822–829. 10.1073/pnas.1523341113. 0027-8424. 26699459. 4743797. free. 2016PNAS..113..822B .
  8. Chung. Shinjae. Weber. Franz. Zhong. Peng. Tan. Chan Lek. Nguyen. Thuc Nghi. Beier. Kevin T.. Hörmann. Nikolai. Chang. Wei-Cheng. Zhang. Zhe. Identification of preoptic sleep neurons using retrograde labelling and gene profiling. Nature. 545. 7655. 477–481. 10.1038/nature22350. 28514446. 5554302. 2017. 2017Natur.545..477C .
  9. Govorunova. Elena G.. Sineshchekov. Oleg A.. Janz. Roger. Liu. Xiaoqin. Spudich. John L.. 2015-08-07. Natural light-gated anion channels: A family of microbial rhodopsins for advanced optogenetics. Science. en. 349. 6248. 647–650. 10.1126/science.aaa7484. 0036-8075. 26113638. 4764398. 2015Sci...349..647G .
  10. Mohammad. Farhan. Stewart. James C. Ott. Stanislav. Chlebikova. Katarina. Chua. Jia Yi. Koh. Tong-Wey. Ho. Joses. Claridge-Chang. Adam. Optogenetic inhibition of behavior with anion channelrhodopsins. Nature Methods. 14. 3. 271–274. 10.1038/nmeth.4148. 28114289. 2017. 4133602.
  11. Mauss. Alex S.. Busch. Christian. Borst. Alexander. 2017-10-23. Optogenetic Neuronal Silencing in Drosophila during Visual Processing. Scientific Reports. En. 7. 1. 13823. 10.1038/s41598-017-14076-7. 29061981. 5653863. 2017NatSR...713823M . 2045-2322.
  12. Govorunova. Elena G.. Cunha. Shane R.. Sineshchekov. Oleg A.. Spudich. John L.. 2016-09-15. Anion channelrhodopsins for inhibitory cardiac optogenetics. Scientific Reports. en. 6. 1. 33530. 10.1038/srep33530. 27628215. 5024162. 2016NatSR...633530G . 2045-2322.
  13. Mardinly. Alan R.. Oldenburg. Ian Antón. Pégard. Nicolas C.. Sridharan. Savitha. Lyall. Evan H.. Chesnov. Kirill. Brohawn. Stephen G.. Waller. Laura. Adesnik. Hillel. 2018-04-30. Precise multimodal optical control of neural ensemble activity. Nature Neuroscience. 21. 6. 881–893. En. 10.1038/s41593-018-0139-8. 29713079. 5970968. 1097-6256.
  14. Mahn. Mathias. Gibor. Lihi. Malina. Katayun Cohen-Kashi. Patil. Pritish. Printz. Yoav. Oring. Shir. Levy. Rivka. Lampl. Ilan. Yizhar. Ofer. 2018. High-efficiency optogenetic silencing with soma-targeted anion-conducting channelrhodopsins. Nature Communications. en. 9. 1. 4125. 10.1038/s41467-018-06511-8. 30297821. 6175909. free. 2018NatCo...9.4125M .
  15. Wietek. Jonas. Broser. Matthias. Krause. Benjamin S.. Hegemann. Peter. 2016-02-19. Identification of a Natural Green Light Absorbing Chloride Conducting Channelrhodopsin from Proteomonas sulcata. Journal of Biological Chemistry. en. 291. 8. 4121–4127. 10.1074/jbc.M115.699637. 0021-9258. 26740624. 4759187. free.
  16. Govorunova. Elena G.. Sineschekov. Oleg A.. Spudich. John L.. 2016-02-01. Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin. Photochemistry and Photobiology. en. 92. 2. 257–263 . 10.1111/php.12558. 26686819. 4914479.
  17. Govorunova. Elena G.. Sineshchekov. Oleg A.. Rodarte. Elsa M.. Janz. Roger. Morelle. Olivier. Melkonian. Michael. Wong. Gane K.-S.. Spudich. John L.. 2017-03-03. The Expanding Family of Natural Anion Channelrhodopsins Reveals Large Variations in Kinetics, Conductance, and Spectral Sensitivity. Scientific Reports. en. 7. 43358. 10.1038/srep43358. 28256618. 5335703. 2017NatSR...743358G . 2045-2322.
  18. Govorunova. Elena G.. Sineshchekov. Oleg A.. Hemmati. Raheleh. Janz. Roger. Morelle. Olivier. Melkonian. Michael. Wong. Gane K.-S.. Spudich. John L.. 2018-05-01. Extending the Time Domain of Neuronal Silencing with Cryptophyte Anion Channelrhodopsins. eNeuro. en. 5. 3. ENEURO.0174–18.2018. 10.1523/ENEURO.0174-18.2018. 2373-2822. 6051594. 30027111.
  19. Wietek. Jonas. Rodriguez-Rozada. Silvia. Tutas. Janine. Tenedini. Federico. Grimm. Christiane. Oertner. Thomas G.. Soba. Peter. Hegemann. Peter. Wiegert. J. Simon. Nov 2017. Anion-conducting channelrhodopsins with tuned spectra and modified kinetics engineered for optogenetic manipulation of behavior. Scientific Reports. 7. 1. 14957. 10.1038/s41598-017-14330-y. 2045-2322. 5668261. 29097684. 2017NatSR...714957W .
  20. Oppermann. Johannes. Fischer. Paul. Silapetere. Arita. Liepe. Bernhard. Rodriguez-Rozada. Silvia. Flores-Uribe. José. Peter. Enrico. Keidel. Anke. Vierock. Johannes. Kaufmann. Joel. Broser. Matthias. 2019-07-25. MerMAIDs: a family of metagenomically discovered marine anion-conducting and intensely desensitizing channelrhodopsins. Nature Communications. en. 10. 1. 3315. 10.1038/s41467-019-11322-6. 2041-1723. 6658528. 31346176. 2019NatCo..10.3315O .
  21. Mahn. Mathias. Prigge. Matthias. Ron. Shiri. Levy. Rivka. Yizhar. Ofer. Biophysical constraints of optogenetic inhibition at presynaptic terminals. Nature Neuroscience. 19. 4. 554–556. 10.1038/nn.4266. 26950004. 4926958. 2016.
  22. Vierock. Johannes. Rodriguez-Rozada. Silvia. Dieter. Alexander. Pieper. Florian. Sims. Ruth. Tenedini. Federico. Bergs. Amelie C. F.. Bendifallah. Imane. Zhou. Fangmin. Zeitzschel. Nadja. Ahlbeck. Joachim. 2021-07-26. BiPOLES is an optogenetic tool developed for bidirectional dual-color control of neurons. Nature Communications. en. 12. 1. 4527. 10.1038/s41467-021-24759-5. 2041-1723. 8313717. 34312384. 2021NatCo..12.4527V .
  23. Wiegert. J. Simon. Mahn. Mathias. Prigge. Matthias. Printz. Yoav. Yizhar. Ofer. Silencing Neurons: Tools, Applications, and Experimental Constraints. Neuron. 95. 3. 504–529. 10.1016/j.neuron.2017.06.050. 28772120. 5830081. 2017.
  24. Evanko. Daniel. Neuroscience: A better way to turn off neurons. Nature Methods. 11. 6. 608. 10.1038/nmeth.2988. 2014. 1699434. free.
  25. Berndt. Andre. Deisseroth. Karl. 2015-08-07. Expanding the optogenetics toolkit. Science. en. 349. 6248. 590–591. 10.1126/science.aac7889. 26250674. 0036-8075. 4776750. 2015Sci...349..590B .

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Anion-conducting channelrhodopsin".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy.