Journal of Neuroscience, Vol 8, 2227-2233, Copyright © 1988 by Society for Neuroscience
Stable and metastable cytoskeletal polymers carried by slow axonal transport
G Filliatreau, P Denoulet, B de Nechaud and L Di Giamberardino
S.H.F.J., Departement de Biologie, CEA, Orsay, France.
The proteins carried by the slow axonal transport in the rat sciatic motor
axons were radiolabeled by injecting 35S-methionine into the spinal cord,
and the distribution of their solubility through the 2 main components of
slow transport (SCa and SCb) was considered. For this purpose, a
cytoskeleton-stabilizing buffer was designed in which a pellet enriched in
macromolecular and polymeric structures was separated from the solubilized
proteins. The monomer/polymer ratios for tubulin were quantified in the 2
rate components. Our results indicate that 90% of the total tubulin was
carried with SCa. Of this, 75% was in a polymeric state, versus only 50% of
the tubulin carried with SCb. The monomeric tubulin recovered in the
soluble fraction was concomitantly transported with the polymerized
microtubules, suggesting that it might represent metastable regions of
these microtubules. The insoluble and soluble fractions of the transported
actin were measured. Actin was mostly (70%) transported with SCb. Of this,
more than 80% was recovered in the soluble fraction, but we cannot say
whether it was in a monomeric or polymeric state, nor if it was transported
free or bound to a structure solubilized during fractionation. The other
30% of the actin, most of it transported with SCa, was recovered in the
polymer- enriched fraction, probably bound to a stabilized polymer, such as
the microtubules.(ABSTRACT TRUNCATED AT 250 WORDS)