5-Hydroxytryptamine, Glutamate, and ATP: Much More Than Neurotransmitters

Rafael Franco; Rafael Rivas-Santisteban; Jaume Lillo; Jordi Camps; Gemma Navarro; Irene Reyes-Resina

doi:10.3389/fcell.2021.667815

5-Hydroxytryptamine, Glutamate, and ATP: Much More Than Neurotransmitters

Front Cell Dev Biol. 2021 Apr 15:9:667815. doi: 10.3389/fcell.2021.667815. eCollection 2021.

Authors

Rafael Franco^{1

2}, Rafael Rivas-Santisteban^{1

2}, Jaume Lillo^{1

2}, Jordi Camps¹, Gemma Navarro^{2

3}, Irene Reyes-Resina¹

Affiliations

¹ Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain.
² Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIberNed), Instituto de Salud Carlos III, Madrid, Spain.
³ Department of Biochemistry and Physiology, School of Pharmacy, University of Barcelona, Barcelona, Spain.

Abstract

5-hydroxytryptamine (5-HT) is derived from the essential amino acid L-tryptophan. Although the compound has been studied extensively for its neuronal handling and synaptic actions, serotonin 5-HT receptors can be found extra-synaptically and not only in neurons but in many types of mammalian cells, inside and outside the central nervous system (CNS). In sharp contrast, glutamate (Glu) and ATP are better known as metabolism-related molecules, but they also are neurotransmitters, and their receptors are expressed on almost any type of cell inside and outside the nervous system. Whereas 5-hydroxytryptamine and Glu are key regulators of the immune system, ATP actions are more general. 5-hydroxytryptamine, ATP and Glu act through both G protein-coupled receptors (GPCRs), and ionotropic receptors, i.e., ligand gated ion channels. These are the three examples of neurotransmitters whose actions as holistic regulatory molecules are briefly put into perspective here.

Keywords: COVID-19; P2 receptors; adenosine receptors; heart; immune system; inflammatory bowel disease; purinergic signaling; serotonin.