Motor-mediated clustering at microtubule plus ends facilitates protein transfer to a bio-mimetic cortex

Polarized protein distributions at the cortex play an important role in the spatial organization of cells. In S. pombe, growing microtubule ends contribute to the establishment and maintenance of such distributions by delivering specific factors to membrane receptors at the poles of the cell. It is however unclear how microtubule plus-end tracking of proteins favours protein accumulation at the cell cortex compared to proteins arriving directly from the cytoplasm. To address this question, we developed an in vitro assay, where microtubules were made to deliver His-tagged plus-end tracking proteins to functionalized microchamber walls. We found that motor-mediated protein clusters formed at microtubule ends were able to transfer to the walls, but non-clustered proteins were not. We further show that this transfer mechanism leads to preferential cluster accumulation at chamber poles, when microtubules are confined to elongated microfabricated chambers with sizes and shapes similar to S. pombe.