Cadherin-mediated regulation of microtubule dynamics

Epithelial polarization and neuronal outgrowth require the assembly of micr otubule arrays that are not associated with centrosomes. As these processes generally involve contact interactions mediated by cadherins, we investiga ted the potential role of cadherin signalling in the stabilization of non-c entrosomal microtubules. Here we show that expression of cadherins in centr osome-free cytoplasts increases levels of microtubule polymer and changes t he behaviour of microtubules from treadmilling to dynamic instability. This effect is not a result of cadherin expression per se but depends on the fo rmation 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 there fore propose that cadherins initiate a signalling pathway that alters micro tubule organization by stabilizing microtubule ends.