Glycine and glycine receptor signaling in immune cells

Abstract

The central nervous system (CNS) is an integration center for signal processing, receiving signals from the different sensory systems and transmitting signals to the motor system. The main cells conducting signals are neurons, and for the largest part of the 20th century most attention of neuroscientist was focused on neurons. A role of glial cells, for a long time considered as passive connective tissue elements, in normal physiology and pathophysiology is now becoming increasingly appreciated. Different neurotransmitter receptors, transporters and enzymes for neurotransmitter synthesis and recycling have been described on glial cells, allowing them to communicate with neurons. This non-neuronal and non-synaptic function of neurotransmitters is mainly studied for glutamate and GABA, the most important excitatory and inhibitory neurotransmitters respectively. This work focused on non-neuronal functions of glycine, another inhibitory neurotransmitter acting mainly in the spinal cord and brainstem, with a special interest in immune cells and its potential role in neuro-immune communication. The starting point of this thesis was the study of “the inhibitory neurotransmitter glycine”. This naming already holds an assumption that is clearly challenged in this work. Indeed glycine working as an inhibitory neurotransmitter implies the amino acid to act on glycine receptors (GlyRs), which is clearly not always the case when discussing non-neuronal functions.