Connexin and Pannexin-Based Channels in Oligodendrocytes: Implications in Brain Health and Disease.

Sebastián Vejar,Juan E Oyarzún,Juan A Orellana,Fernando C Ortiz,Mauricio A Retamal

doi:10.3389/fncel.2019.00003

Abstract

Oligodendrocytes are the myelin forming cells in the central nervous system (CNS). In addition to this main physiological function, these cells play key roles by providing energy substrates to neurons as well as information required to sustain proper synaptic transmission and plasticity at the CNS. The latter requires a fine coordinated intercellular communication with neurons and other glial cell types, including astrocytes. In mammals, tissue synchronization is mainly mediated by connexins and pannexins, two protein families that underpin the communication among neighboring cells through the formation of different plasma membrane channels. At one end, gap junction channels (GJCs; which are exclusively formed by connexins in vertebrates) connect the cytoplasm of contacting cells allowing electrical and metabolic coupling. At the other end, hemichannels and pannexons (which are formed by connexins and pannexins, respectively) communicate the intra- and extracellular compartments, serving as diffusion pathways of ions and small molecules. Here, we briefly review the current knowledge about the expression and function of hemichannels, pannexons and GJCs in oligodendrocytes, as well as the evidence regarding the possible role of these channels in metabolic and synaptic functions at the CNS. In particular, we focus on oligodendrocyte-astrocyte coupling during axon metabolic support and its implications in brain health and disease.

Highlights

Oligodendrocytes are the myelin-forming cells of the central nervous system (CNS)
The evidence discussed in this review indicates that both oligodendrocyte-oligodendrocyte coupling and oligodendrocyte-astrocyte coupling play a pivotal role in forming a functional panglial syncytium supporting the buffering of extracellular K+ and metabolic supply to axons
The available literature suggests that oligodendrocyte progenitors would not contribute to this functional syncytial network, their role could not be completely ruled out based on recent findings showing the coupling of oligodendrocyte precursor cells (OPCs) with astrocytes through Cx47 (Liu et al, 2017; Xu et al, 2017)

Summary

Introduction

Oligodendrocytes are the myelin-forming cells of the central nervous system (CNS). They were first described and characterized as small cells with many branches distributed ubiquitously within the CNS in a close spatial relationship with axons (del Río-Hortega, 1922; Ramón y Cajal, 1925). We review and discuss the evidence sustaining the possible role of oligodendrocyte GJ coupling in the coordination of metabolic support for neuronal activity, as well as its participation in demyelination processes observed in different diseases.

Results

Conclusion