2019-10-27 19:55:50
All daily activities depend on communication between neurons, which in turn depends on molecular mechanisms that occur continuously at high speed in the area of neuronal interaction, the so-called synapse. Let us remember that the synapse works through the release into the synaptic space by a neuron of small molecules, called neurotransmitters, which interact with receptor molecules present in the other neuron and send them an activating signal.
In order for synapses to function at the required speed, neurons synthesize neurotransmitters in advance and store them in vesicles that are like tiny bubbles inside cells, whose surface is similar to that of the cell membrane. To release the neurotransmitters contained in the vesicles into the synapse space, the vesicles must fuse with the cell membrane.
To achieve this, neurons form structures on their outer membrane called porosomes, that is, pore-forming bodies. These porosomes are very small, only about 10 to 15 nanometers in length, so in just one millimeter 66,000 to 100,000 porosomes would fit. The vesicle and cell membranes come into contact, but fusion of the vesicle with the membrane only occurs when the biochemical signal is received.
The studies carried out on synapses, since Ramón y Cajal discovered them, have revealed the proteins that facilitate the fusion of vesicles with the membrane. This earned its discoverers the Nobel Prize in Medicine in 2013. However, the protein molecules responsible for the initial braking mechanism of this fusion were still unknown. These proteins form a kind of central plug of the porosome, in the contact zone between the vesicle and the membrane.
Researchers at the University of Wisconsin, in the US, have now discovered the proteins that form the porosome plug and prevent the release of neurotransmitters into the synaptic gap unless the biochemical signal is received. The most important protein in this plug is called synaptotagmin-1 and its existence was already known. What was not known was its important role as part of the plug that regulates vesicle fusion at synapses.
This discovery adds to other previous ones from the same research group that revealed that porosomes are not just open or closed gates, but rather function as true control valves for the fusion of synaptic vesicles.
Reference:
Nicholas A. Courtney et al. Synaptotagmin 1 clamps synaptic vesicle fusion in mammalian neurons independent of complexin. Nature Communications (2019). |
Jorge Laborda, October 27, 2019
Reference:
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