Microtubules and Axonal Transport Defects

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By Benjamin Musrie, Medical Researcher. Sydney, Australia.

Illustration by Jenny Liu

The cells cytoskeleton is a dynamic network composed of three main components — microfilaments, intermediate filaments and microtubules. The cytoskeleton gives the cell its shape and provides mechanical support that enables the cell to carry out functions such as division and movement. Microtubules are microscopic tubes made up of alpha and beta tubulin heterodimers which undergo continuous polymerisation and depolymerisation. They are involved in cell division, organisation of intracellular structure and intracellular transport. Axonal transport is one of the most critical functions of microtubules and is crucial for neuronal homeostasis. Defects in axonal transport is considered one of the earliest pathophysiological events in ALS and may be a primary cause of motor neuron degeneration.

Axonal transport:

Axonal transport is defined as the process by which proteins, organelles and other molecules synthesised in the neurosome are transported to and from nerve endings. Axonal transport is essential for the growth and survival of neurons. Microtubules extend throughout the neuron and act as the ‘tracks’ for this form of transportation. Kinesin and Dynein motor proteins facilitate the transport of various cargo along these…