Endomembrane system in our cells. Vesicles carrying cargo molecules move between different cell compartments. (by Mariana Ruiz LadyofHats [Public domain], via Wikimedia Commons)
Most of our cells are just micrometers in size but they contain millions of molecules, some are small as glucose, others – colossal in size as large proteins and nucleic acids. Some of the molecules form rather static structures inside cells, being a part of cytoskeleton, and even those get reorganised all the time. Most of the others are constantly moving about cell, yet not in a chaotic way.
Cellular processes need to be quick and targetted. The cell is not a pouch containing molecular soup, it’s more like a tiny but sophisticated machine.
Here comes a problem – if a compound, a protein let’s say, need to be delivered to a specific location in cell, how would it go about it?
For this, cells have a complex transport system: a shipping place dispatches vesicules labelled with specific transport and docking proteins and the destination point has another lore of molecules to recognise the labels. This is a system akin to our mail service with vesicules being stamped and signed envelopes.
This week 2013 Nobel Prize in Medicine was awarded to James E Rothman, Randy W Schekman and Thomas C Südhof for their work on the mechanincs of intracellular trafficking. My first reaction was, ’Oh, I thought they gave it for this ages ago.’
Indeed, the first studies on the vesilular tranport in yeasts were published in 1979 and since then the molecular machinery regulating specific trafficking of vesicules to the dedicated cellular destinations has been characterised at high resolution.
Now what happens if this system breaks? Mutations in the transport proteins lead to a numbe rof disporders, especially of the nervous system.
Vesicular trafficking in neurons (video-microscopy)
Neurons are big cells with very lengthy parts – axons and dendrites. To trasmit signals neurons need to produce neuromediators, chemicals regulating permeability of ion channels and, therefore, neuronal electrochemical conductivity. These chemicals produced in the neuron body and need to be transported far away to axon ends or termini that contact other neurons or muscle cells. The contact structure is called synapse.
If the system breaks, the nervous system cannot function properly and it leads to neural disorders, including Alzheimers disease. To find out more about connection between vesicular trafficking in cells and human diseases read this free review.
This Nobel Prize-awarded discovery has direct biomedical applications. Drugs affecting intracellular transport, for instance, those stabilising cytoskeleton and sustaining axonal transport, could help to prevent trafficking-linked diseases.