Actin-microtubule coordination at growing microtubule ends

To power dynamic processes in cells, the actin and microtubule cytoskeletons organize into
complex structures. Although it is known that cytoskeletal coordination is vital for cell
function, the mechanisms by which cross-linking proteins coordinate actin and microtubule
activities remain poorly understood. In particular, it is unknown how the distinct mechanical
properties of different actin architectures modulate the outcome of actin–microtubule
interactions. To address this question, we engineered the protein TipAct, which links growing
microtubule ends via end-binding proteins to actin filaments. We show that growing
microtubules can be captured and guided by stiff actin bundles, leading to global
actin–microtubule alignment. Conversely, growing microtubule ends can transport, stretch
and bundle individual actin filaments, thereby globally defining actin filament organization.
Our results provide a physical basis to understand actin–microtubule cross-talk, and reveal
that a simple cross-linker can enable a mechanical feedback between actin and microtubule
organization that is relevant to diverse biological contexts.