Profilin connects Actin Assembly with Microtubule dynamics

Nejedla, M., Sara, S., Sulimenko, V., de Almeida, FN., Blom, H., Draber, P., Aspenström, P., Karlsson, R.

Mol Biol Cell. 2016 Jun 15. pii: mbc.E15-11-0799.

Abstract

Profilin controls actin nucleation and assembly processes in eukaryotic cells. Actin nucleation and elongation promoting factors (NEPFs) such as Ena/VASP, formins and WASP family proteins recruit profilin:actin for filament formation; some of these are found to be microtubule-associated, making actin polymerization from microtubule-associated platforms possible. Microtubules are implicated in focal adhesion turn-over, cell polarity establishment and migration, illustrating the coupling between actin and microtubule systems. Here we demonstrate that profilin is functionally linked to microtubules with formins and point to formins as major mediators of this association. To reach this conclusion we combined different fluorescence microscopy techniques including super resolution microscopy with siRNA-modulation of profilin expression and drug treatments to interfere with actin dynamics. Our studies show that profilin dynamically associates with microtubules and that this fraction of profilin contributes to balance actin assembly during homeostatic cell growth and impacts on microtubule dynamics. Hence profilin functions as a regulator of microtubule (+)-end turn-over in addition to being an actin control element.