The C. elegans Taste Receptor Homolog LITE-1 Is a Photoreceptor

Abstract

SummaryMany animal tissues/cells are photosensitive, yet only two types of photoreceptors (opsins and cryptochromes) have been discovered in metazoans. The question arises as to whether unknown types of photoreceptors exist in the animal kingdom. LITE-1, a seven-transmembrane gustatory receptor (GR) homolog, mediates UV light-induced avoidance behavior in C. elegans. However, whether LITE-1 functions as a chemoreceptor or photoreceptor has not been determined. Here, we show that LITE-1 directly absorbs both UVA and UVB light with an extinction coefficient 10-100 times that of opsins and cryptochromes, indicating that LITE-1 is highly efficient in capturing photons. Unlike typical photoreceptor proteins employing a prosthetic chromophore to capture photons, LITE-1 strictly depends on its protein conformation for photon absorption. We further identified two tryptophan residues critical for LITE-1 function. Interestingly, unlike GPCRs, LITE-1 adopts a reversed membrane topology. Thus, LITE-1, a taste receptor homolog, represents a distinct type of photoreceptor in the animal kingdom.

NeuroPAL: A Neuronal Polychromatic Atlas of Landmarks for Whole-Brain Imaging inC. elegans

“…We used the microfluidic device to deliver taste and odor cues that are perceived by the worm in a lateralized manner: a) a repulsively high concentration of the gustatory cue NaCl, previously shown to trigger an ON response in the left ASE and an OFF response in the right ASE (Suzuki et al, 2008), b) the attractive odorant 2-butanone, which is sensed by AWC-ON, stochastically chosen in development as either the left or right AWC neuron (Wes and Bargmann, 2001) and, c) the attractive odorant 2,3pentanedione which evokes the opposite lateralized response in AWC-OFF (the AWC neuron contralaterally opposed to the one sensing 2-butanone) (Wes and Bargmann, 2001). We also delivered repulsive blue light (via laser), previously shown to evoke its avoidance response through LITE-1, a photoreceptor protein (Edwards et al, 2008;Gong et al, 2017). Hence, these four stimuli provided an opportunity to measure circuit responses for three sensory modalities, representing both attractive and repulsive valences, while exploring the downstream representations of asymmetric sensory inputs.…”

Cross talk between calcium and ROS regulate the UVA‐induced melanin response in human melanocytes

“…Our proposed model adds to the increasing evidence for ROS acting as second messengers and for light-induced ROS mediating various signaling pathways. [26][27][28][29][30] Our findings propose a novel role for mitochondria in UVR-induced skin pigmentation. Mitochondria are vital for cellular homeostasis, as they regulate cellular energy, metabolism, survival, and apoptosis.…”

LITE-1 Dependent X-Ray Sensitivity in C. elegans

“…While the response appeared intact in the GUR-3 null strain, it was severely deficient in the two strains lacking functional LITE-1. LITE-1 and GUR-3 share 40% homology and are both involved in the inhibition of feeding response to UV light Gong et al 2016); however, only LITE-1 is thought to participate in the avoidance response, as the response appears intact in GUR-3 mutants . Therefore, our finding that X-ray avoidance also appears intact in the strain with mutated GUR-3, but functional LITE-1, is in line with previous findings demonstrating a prominent role for LITE-1, but not GUR-3, in locomotory avoidance behavior.…”