Microbial light-activatable proton pumps as neuronal inhibitors to functionally dissect neuronal networks in **C. elegans**

Husson, Steven J.; Liewald, Jana F.; Schultheis, Christian; Stirman, Jeffrey N.; Lu, Hang; Gottschalk, Alexander

doi:10.1371/JOURNAL.PONE.0040937

Title

Microbial light-activatable proton pumps as neuronal inhibitors to functionally dissect neuronal networks in **C. elegans**

Author

Husson, Steven J.

Liewald, Jana F.

Schultheis, Christian

Stirman, Jeffrey N.

Lu, Hang

Gottschalk, Alexander

Abstract

Essentially any behavior in simple and complex animals depends on neuronal network function. Currently, the best-defined system to study neuronal circuits is the nematode Caenorhabditis elegans, as the connectivity of its 302 neurons is exactly known. Individual neurons can be activated by photostimulation of Channelrhodopsin-2 (ChR2) using blue light, allowing to directly probe the importance of a particular neuron for the respective behavioral output of the network under study. In analogy, other excitable cells can be inhibited by expressing Halorhodopsin from Natronomonas pharaonis (NpHR) and subsequent illumination with yellow light. However, inhibiting C. elegans neurons using NpHR is difficult. Recently, proton pumps from various sources were established as valuable alternative hyperpolarizers. Here we show that archaerhodopsin-3 (Arch) from Halorubrum sodomense and a proton pump from the fungus Leptosphaeria maculans (Mac) can be utilized to effectively inhibit excitable cells in C. elegans. Arch is the most powerful hyperpolarizer when illuminated with yellow or green light while the action spectrum of Mac is more blue-shifted, as analyzed by light-evoked behaviors and electrophysiology. This allows these tools to be combined in various ways with ChR2 to analyze different subsets of neurons within a circuit. We exemplify this by means of the polymodal aversive sensory ASH neurons, and the downstream command interneurons to which ASH neurons signal to trigger a reversal followed by a directional turn. Photostimulating ASH and subsequently inhibiting command interneurons using two-color illumination of different body segments, allows investigating temporal aspects of signaling downstream of ASH.

Language

English

Source (journal)

PLoS ONE

Publication

2012

ISSN

1932-6203

DOI

10.1371/JOURNAL.PONE.0040937

Volume/pages

7 :7 (2012) , 14 p.