Care Packages for your Neurons
No neuron is an island. It comes as no surprise that the cells that are responsible for something as profound as our thoughts require a lot of support. Neurons are supported by cells known as ‘glial cells’. Optimal brain function depends on glial cells and neurons communicating with each other. But how does this happen at the molecular level? In a fascinating study, published in the #OpenAccess journal PLOS Biology , researchers in Germany find tantalizing answers to just these questions (http://goo.gl/ojrGuB). I have also written a more in-depth analysis of this paper with more neuroscience terms explained in detail here in this KnowTheCosmos article (http://goo.gl/2j7Sel)
✤ ‘Oligodendrocytes‘ are a type of glial cell that forms the myelin sheath that insulates neurons from the environment and from each other. Oligodendrocytes also frequently release vesicles known as exosomes; think of them as small bubbles containing various molecules such as proteins and RNA.
✤ The researchers looked into the mechanism by which exosomes might be released from the oligodendrocytes. Their results show that the neurotransmitter glutamate is released from active neurons, and it causes the release of exosomes from the nearby oligodendrocytes.
✤ Since glutamate is released from active neurons, the next question was whether neuronal activity is linked to the release of exosomes. The researchers artificially stimulated electrical activity in the neurons, and sure enough they observed an increase in the number of exosomes released by the nearby oligodendrocytes.
✤ What happens to these released exosomes? Researchers used fluorescent-labeled exosomes and watched what happens in neurons grown in petri dishes. They saw that neurons take up the exosomes, and the payload is effectively delivered inside. In this fantastic image below, the neuron is red, and the exosome is highlighted in green.
✤ How do these exosomes help neurons? Exosomes carry various molecules such as proteins and RNA. Under optimal conditions, the neurons can survive fine without oligodendrocytes. However, when the researchers starved and stressed the neurons, the neurons growing in the presence of exosome-secreting oligodendrocytes could withstand these assaults much better than those grown alone.
✤ These findings are amazing, because it shows that these exosomes support neurons under conditions of cell stress, suggesting that they have a role in neuroprotection. The cell communication works both ways, because the neurons communicate with the oligodendrocytes (neurons release glutamate, making the oligodendrocytes release exosomes), and the oligodendrocytes communicate with the neurons by producing these neuroprotective care-packages, the exosomes, to soothe damaged and tired neurons!
✤ Oligodendrocytes were long thought to provide just insulation for neurons. This work shows that they do more than that, and play an active role in supporting our hard-working neurons, by delivering a molecular care package. As we understand more about the complex relationship between nerve cells and the cells that nurture them, we are better able to understand what happens when things go wrong, be it brain damage or neurodegenerative diseases too.
Image: An exosome (green) taken up by a neuron (red). Cell nucleus stained blue.
Image credit: Eva-Maria Krämer-Albers