title: Hemichannels: new pathways for gliotransmitter release.
abstract: Growing evidence suggests that glial cells express virtually all known types of neurotransmitter receptors, enabling them to sense neuronal activity and microenvironment changes by responding locally via the Ca(2+)-dependent release of bioactive molecules, known as "gliotransmitters". Several mechanisms of gliotransmitter release have been documented. One of these mechanisms involves the opening of plasma membrane channels, known as hemichannels. These channels are composed of six protein subunits consisting of connexins or pannexins, two highly conserved protein families encoded by 21 or 3 genes, respectively, in humans. Most data indicate that under physiological conditions, glial cell hemichannels have low activity, but this activity is sufficient to ensure the release of relevant quantities of gliotransmitters to the extracellular milieu, including ATP, glutamate, adenosine and glutathione. Nevertheless, it has been suggested that dysregulations of hemichannel properties could be critical in the beginning and during the maintenance of homeostatic imbalances observed in several brain diseases. In this study, we review the current knowledge on the hemichannel-dependent release of gliotransmitters in the physiology and pathophysiology of the CNS.
authors.affiliation: Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: T D
authors.initials: TD
authors.lastname: Montero
authors.affiliation: Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: jaorella@uc.cl.
authors.forename: J A
authors.initials: JA
authors.lastname: Orellana
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D017630:Connexins / Q000378:metabolism*; D006801:Humans; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D015398:Signal Transduction; D009435:Synaptic Transmission
chemical_list: D017630:Connexins; D000255:Adenosine Triphosphate
keywords: astrocyte; connexin; hemichannel; microglia; neuron; pannexin