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[Report] Accelerated actin filament polymerization from microtubule plus ends

ScienceNOW - Fetched: May 19th, 2016, 4:00pm UTC

Microtubules (MTs) govern actin network remodeling in a wide range of biological processes, yet the mechanisms underlying this cytoskeletal cross-talk have remained obscure. We used single-molecule fluorescence microscopy to show that the MT plus-end–associated protein CLIP-170 binds tightly to formins to accelerate actin filament elongation. Furthermore, we observed mDia1 dimers and CLIP-170 dimers cotracking growing filament ends for several minutes. CLIP-170–mDia1 complexes promoted actin polymerization ~18 times faster than free–barbed-end growth while simultaneously enhancing protection from capping proteins. We used a MT-actin dynamics co-reconstitution system to observe CLIP-170–mDia1 complexes being recruited to growing MT ends by EB1. The complexes triggered rapid growth of actin filaments that remained attached to the MT surface. These activities of CLIP-170 were required in primary neurons for normal dendritic morphology. Thus, our results reveal a cellular mechanism whereby growing MT plus ends direct rapid actin assembly. Authors: Jessica L. Henty-Ridilla, Aneliya Rankova, Julian A. Eskin, Katelyn Kenny, Bruce L. Goode

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