Possibly related: I've seen at least one study in which they've found the misfolded protein (alpha synuclein) in the guts of people who had had Parkinson's (where it's a 'marker' in the CNS, particularly the substantia nigra).

Soo... vagus nerve? Motor proteins haul stuff up and down the entire length of an axon...

Speaking of motor proteins, here’s one of my favorite videos of one. :-)