A novel action of collapsin: collapsin-1 increases antero- and retrograde axoplasmic transport independently of growth cone collapse

Chick collapsin-1, a member of the by a mechanism distinct from that causing growth semaphorin family, has been implicated in axonal cone collapse. Pertussis toxin (PTX) but not its B pathfinding as a repulsive guidance cue. Collapsin-1 induces growth cone collapse via a pathway which oligomer blocks collapsin-induced growth cone col- may include CRMP-62 and heterotrimeric G proteins. lapse. The holotoxin does not affect collapsin-stimu- CRMP-62 protein is related to UNC-33, a nematode lated axoplasmic transport. Mastoparan and a myelin neuronal protein required for appropriately directed protein NI-35 induce PTX-sensitive growth cone col- axonal extension. Mutations in unc-33 affect neural lapse but do not stimulate axoplasmic transport. microtubules, the basic cytoskeletal elements for axo- These results provide evidence that collapsin has a plasmic transport. Using computer-assisted video-en- unique property to activate axonal vesicular transport hanced differential interference contrast microscopy, systems. There are at least two distinct pathways we now demonstrate that collapsin-1 potently pro- through which collapsin exerts its actions in motes axoplasmic transport. Collapsin-1 doubles the developing neurons. q 1997 John Wiley & Sons, Inc. J number of antero- and retrograde-transported organ- Neurobiol 33: 316-328, 1997 elles but not their velocity. Collapsin-1 decreases the Keywords: collapsin; axoplasmic transport; nerve number of stationary organelles, suggesting that the growth cone; pertussis toxin; G proteins fraction of time during which a particle is moving is