Journal of Neuroscience, Vol 7, 3695-3702, Copyright © 1987 by Society for Neuroscience
Taxol interferes with the interaction of microtubule-associated proteins with microtubules in cultured neurons
MM Black
Department of Anatomy, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Treatment of neurons with taxol leads to the formation of microtubule
bundles in which individual microtubules are much more closely spaced than
in untreated neurons (Letourneau and Ressler, 1984). This suggests that
taxol interferes with the mechanisms that regulate microtubule spacing in
situ. I have determined whether treatment of neurons with taxol alters the
composition of their microtubules, reasoning that such alterations may be
related to the taxol-induced alterations in microtubule spacing. Cultures
of sympathetic neurons were incubated with 35S-methionine and either taxol,
podophyllotoxin, a potent microtubule-depolymerizing agent, or dimethyl
sulfoxide (DMSO), the solvent for the drugs. The levels of labeled
microtubule-associated proteins (MAPs) assembled into microtubules in the
various cultures were then assayed biochemically. I focused on 4 MAPs: tau,
chartins, MAP-2, and the MAP with a molecular mass of 210,000 Da (210 kDa).
In untreated cultures, these MAPs are prominent components of microtubules.
The levels of all MAPs, as well as tubulin, in microtubules were greatly
reduced in cultures treated with podophyllotoxin, compared to controls.
Taxol had varied effects on the interaction of MAPs with microtubules in
situ. Microtubules formed in the presence of taxol contained normal or
slightly elevated levels of tau and the 210 kDa MAP compared to
microtubules in control cultures. In contrast, microtubules formed in the
presence of taxol were almost completely devoid of chartin MAPs and MAP-2
compared to controls. These results show that taxol interferes with the
interaction of some, but not all, MAPs with microtubules in situ. The
altered MAP composition of microtubules in taxol-treated neurons may
contribute to the abnormal spacing of microtubules seen in such neurons.