Signaling in the Chemosensory Systems

Abstract

The small nematode Caenorhabditis elegans lives in the soil, where mechanical, thermal and most of all chemical stimuli strongly influence its behavior. Here we briefly review how chemical sensitivity is organized at the cellular and molecular level in this organism. C. elegans has less than 40 chemosensory neurons. With few exceptions each neuron senses more than one substance and each substance is sensed by more than one neuron. At the molecular level, as in other organisms, also in C. elegans, seven transmembrane G-protein-coupled receptors (GPCRs), heterotrimeric G proteins, cyclic nucleotidegated ion channels, TRP channels and Ca++ play crucial roles in chemical sensitivity. An unusual feature, possibly due to C. elegans's strong dependence on chemical cues, is the very large number of GPCR chemoreceptor genes (1300-1700) coded in its genome. Genetic approaches have also allowed the identification of new molecules involved in chemical sensitivity that would not have been discovered otherwise. In addition to the basic factors involved in primary signalling, the studies in C. elegans have revealed a network of regulatory pathways and molecules suggesting that fine modulation of the responsiveness of neurons is important, possibly to allow worms to negotiate a continuously changing environment. The experimental versatility of C. elegans has made it possible, in many cases, to determine precisely in which neuron a given molecule or pathway is required and for which biological response. This type of information can contribute to the general field of sensory signalling because it provides correlations between the biochemical properties of molecules and their cellular functions and between these and the in vivo behavioral responses of the animal.

Microfluidic Device to Measure the Speed of C. elegans Using the Resistance Change of the Flexible Electrode

“…The locomotion of C. elegans is a feature that can ascertain its condition initiated by an external stimulus. This locomotion is a natural behavior that enables C. elegans to move to favorable surroundings (e.g., a location of food), or to escape from harmful and noxious stimuli [ 16 , 17 , 18 , 19 ]. When C. elegans moves on the surface, the worm’s movement exhibits an undulatory crawling motion ( i.e.…”

Sensory Perception and Aging in Model Systems: From the Outside In

“…Here we touch on a few important concepts of sensory biology that are particularly related to chemosensation, because of its link with longevity. A detailed discussion of the recent advances in other sensory modalities, such as vision or pain reception, sensory signal transduction, anatomy, neurophysiology, or learning/memory can be found in a number of excellent reviews ( C. elegans (Bargmann 2006, Bergamasco & Bazzicalupo 2006), D. melanogaster (Gerber et al 2009, Masse et al 2009, Vosshall & Stocker 2007)).…”

AIM interneurons mediate feeding suppression through the TYRA-2 receptor in C. elegans

“…C. elegans is equipped with multiple sensory modalities that can detect various environmental cues, including odors, tastes, osmolarity, temperature, and mechanical touch. It can sense hundreds of water-soluble and volatile molecules, which can evoke distinct behaviors, such as attraction, avoidance, mating, or feeding (Bargmann 2006 ; Bergamasco and Bazzicalupo 2006 ).…”