Epidermal cells and sensory neurons team up

Abstract

Experiments in fruit fly larvae show that epidermal cells can communicate with sensory neurons to drive responses to pain.

Keywords: D. melanogaster; epidermis; genetics; genomics; mechanosensation; neuroscience; nociception; somatosensation.

Figure 1.. Communication between epidermal cells and pain-sensing neurons in fruit fly larvae.

(A) Fruit fly larvae (shape on left hand side) are covered in pain-sensing neurons (black) that lie ensheathed beneath epidermal cells (beige). Within each epidermal cell are vesicles containing molecules that influence neuron behavior (neuromodulators; pink circles), as well as protein channels called Orai (blue) that transmit calcium ions (green), which sit inactive at the cell surface (B) A painful mechanical stimulus (depicted as brown rectangular shape) elicits a response that causes the larvae to bend into a C-shape. The stimulus causes calcium to flow into epidermal cells via the Orai channels and trigger the release of neuromodulators (the specific nature of which remains unknown) from vesicles. The combination of intrinsic neuronal properties and the presence of neuromodulators strongly activates pain-sensing neurons. (C) When Orai is mutated to be non-functional, epidermal cells cannot take in calcium, which prevents the release of neuromodulators, weakening the activation of the sensory neurons. (D) Once a painful mechanical input has been applied, the neuromodulators released by epidermal cells ensure that pain-sensing neurons remain sensitive to the stimuli – a process known as sensitization. If a larva receives subsequent painful cues, the neurons will be more easily activated and ready to facilitate escape behaviors.