Direct evidence for the interaction of stathmin along the length and the plus end of microtubules in cells

Abstract

Stathmin is aprominent destabilizer of microtubules (MTs). Extensive in vitro studieshave strongly suggested that stathmin could act by sequestering tubulin and/or by binding to MT tips. In cells, the molecular mechanisms of stathmin binding to tubulin and/or MTs and its implications for the MT dynamics remain unexplored. By using immunofluorescence resonance energy transfer and fluorescence recovery after photobleaching,we analyzed the ability of stathmin and its phosphorylated forms (on Ser16, -25, -38, and -63) to interact with tubulin and MTs in A549 cells. Consistent with in vitro studies, we detected stathmin tubulin interactions at the MT plus ends and in the cytosol. Of interest,we also observed a novelpool of stathminbound along theMT.Expression of truncated stathmin anduse ofMTstabilizing taxol furthershowedthat theC-terminaldomainof stathminis themain contributor to this binding andthat the phosphorylation state of stathmin plays a role in its binding along theMTwall. Our findings demonstrate that stathmin binds directly along the MT wall. This pool of stathmin would be readily available to participate in protofilament dissociationwhen the moving plus end of a depolymerizingMTreaches stathminmolecules.-Nouar, R., Breuzard, G., Bastonero, S.,Gorokhova, S., Barbier, P.,Devred, F.,Kovacic,H., Peyrot,V.Direct evidence for the interaction of stathmin along the length and the plus end of microtubules in cells.