In neurons, kinesin is the motor protein that facilitates anterograde axonal transport of mitochondria from the cell body to the synapse, while dynein is the motor protein that facilitates retrograde transport of mitochondria from the synapse to the cell body, where they can become recharged.
Microtubules are composed of dimers of alpha-tubulin and beta-tubulin, arranged in a tubular shape containing 13 copies of this elongated straw-like structure. Microtubules in axons are polarized, with the plus end pointing toward the synapse, while the minus end points toward the microtubule organizing center. Microtubules are stabilized by the protein, tau, which, when hyperphosphorylated, falls off the microtubules, causing destabilization, with consequent retrograde transport of mitochondria to the cell body and corresponding decreased production of localized ATP. The modified protein that falls off the microtubules leads to formation of neurofibrillary tangles, which are highly detrimental to neurons.