Emerging roles of exosomes in neuron-glia communication - PubMed (original) (raw)

Emerging roles of exosomes in neuron-glia communication

Carsten Frühbeis et al. Front Physiol. 2012.

Abstract

Brain function depends on coordinated interactions between neurons and glial cells. Recent evidence indicates that these cells release endosome-derived microvesicles termed exosomes, which are 50-100 nm in size and carry specific protein and RNA cargo. Exosomes can interact with neighboring cells raising the concept that exosomes may mediate signaling between brain cells and facilitate the delivery of bioactive molecules. Oligodendrocytes myelinate axons and furthermore maintain axonal integrity by an yet uncharacterized pathway of trophic support. Here, we highlight the role of exosomes in nervous system cell communication with particular focus on exosomes released by oligodendrocytes and their potential implications in axon-glia interaction and myelin disease, such as multiple sclerosis. These secreted vesicles may contribute to eliminate overproduced myelin membrane or to transfer antigens facilitating immune surveillance of the brain. Furthermore, there is emerging evidence that exosomes participate in axon-glia communication.

Keywords: axon–glia interaction; exosomes; microvesicles; myelin disease; neuron–glia communication; oligodendrocytes.

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Figures

Figure 1

Figure 1

Characteristics of oligodendroglial exosomes. (A) Electron micrograph of exosomes in the extracellular space released by primary oligodendrocytes. Immuno-gold labeling was performed with antibodies recognizing myelin-associated glycoprotein (MAG). Asterisk indicates the putative MVB fusion profile that resulted in exosome release. Scale bar, 100 nm. (B) Protein composition of a typical oligodendroglial exosome. The illustration is based on proteomic analyses of exosome preparations derived from oligodendroglial cells (Krämer-Albers et al., 2007).

Figure 2

Figure 2

Postulated roles of microvesicles in neural cell communication. Neural cells release different types of microvesicles with several known or suggested functions. Neurons secrete exosomes which may influence synaptic plasticity. Microglia modulate neurotransmission via shedding microvesicles. Astrocyte-derived exosomes carry neuroprotective cargo and could contribute to neuronal survival. Neuronal signals trigger exosome release from oligodendrocytes by raising intracellular Ca2+-levels. Upon internalization by neurons these exosomes could provide support to axons. Microglia take up and degrade oligodendroglial exosomes without changing their inflammatory properties. Under specific pathological conditions these exosomes may transfer antigens to microglial cells or other APCs and induce inflammatory responses.

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