When the protein dynein was discovered to provide the flagellar bending force to axonemal microtubules (MTs) (Gibbons, 1963), “people had jumped to the reasonable hypothesis that dynein was perhaps also involved in other microtubule movements,” recalls Richard Vallee (Columbia University Medical Center, New York, NY). But by the 1980s, no such cytoplasmic motor proteins had been found.
In the summer of 1985, Vallee recalls seeing work on axonal transport in the squid axoplasm from the labs of Michael Sheetz and Ray Lasek at the Woods Hole Marine Biology Laboratory. “The thinking about axonal transport was all over the place before that,” he says. Observations of fast axonal transport argued against a passive mechanism, but no one had found a mechanism to support theories like cytoplasmic streaming along the MTs. “But now,” says Vallee, “there was good evidence that there might be specific molecules responsible for...
