Dephosphorylation suppresses the activity of neurofilament to promote tubulin polymerization.

The phosphate content of neurofilament was diminished by half, from 49.4 to 22.9 nmol/mg, by treatment with alkaline phosphatase. Dephosphorylation decreased the activity of neurofilament to promote tubulin assembly. This suppression was supposed to be mainly due to dephosphorylation of the 200 kDa subunit of neurofilament. Dephosphorylation of the isolated 200 kDa subunit caused suppression of its activity to promote tubulin polymerization. These results suggest that changes in the phosphate content modulate interaction of neurofilament with tubulin.