Set to signal
The image above depicts a false-colored cross-section view of a synapse – the junction where signals pass from a neuron to another cell. The green-colored synaptic bouton (button) is a knoblike swelling at the end of a neuronal axon. It’s the megaphone, so to speak, through which a neuron talks to the rest of the world.
In this image, the bouton is surrounded by an insulating glial cell (speckled purple) that bumps up against a muscle fiber, the recipient of neuronal signals.
The thin, dark purple gap between the bouton and fiber is the synaptic cleft. Signal molecules are released by the bouton into this space and taken up by receptors on the receiving cell. Inside the bouton itself are mitochondria (dark blue circles), the power plants of cells, and vesicles (smaller, green circles) filled with yellow neurotransmitters.
The green vesicles take on particular celebratory note this week. The Nobel Prize for medicine or physiology was awarded yesterday to a trio of researchers – James E. Rothman, Randy W. Schekman and Thomas C. Sudhof – for their ground-breaking discoveries about the nature and functions of vesicles.
In citing their work, the Nobel Prize committee explained that the newly minted laureates had solved the mystery of how cells organize their transport system.
“Each cell is a factory that produces and exports molecules,” wrote the committee in their announcement. “For instance, insulin is manufactured and released into the blood and chemical signals called neurotransmitters are sent from one nerve cell to another. These molecules are transported around the cell in small packages called vesicles. The three Nobel Laureates have discovered the molecular principles that govern how this cargo is delivered to the right place at the right time in the cell.”
You can read the full Nobel Prize release here.