Cadherin-mediated regulation of microtubule dynamics.

Epithelial polarization and neuronal outgrowth require the assembly of microtubule arrays that are not associated with centrosomes. As these processes generally involve contact interactions mediated by cadherins, we investigated the potential role of cadherin signalling in the stabilization of non-centrosomal microtubules. Here we show that expression of cadherins in centrosome-free cytoplasts increases levels of microtubule polymer and changes the behaviour of microtubules from treadmilling to dynamic instability. This effect is not a result of cadherin expression per se but depends on the formation of cell-cell contacts. The effect of cell-cell contacts is mimicked by application of beads coated with stimulatory anti-cadherin antibody and is suppressed by overexpression of the cytoplasmic cadherin tail. We therefore propose that cadherins initiate a signalling pathway that alters microtubule organization by stabilizing microtubule ends.