Microtubule-actin interactions in vitro

Celine Alkemade
Collaborators: Gijsje Koenderink (AMOLF), Anna Akhmanova (University Utrecht), Bela Mulder (AMOLF), Pieter Rein ten Wolde (AMOLF).

The actin and microtubule (MT) cytoskeletons are key structural components that allow and coordinate rapid and sometimes drastic changes in cellular morphology, such as polarization, migration and cytokinesis. Most studies focus on the independent functions and characteristics of these two elements; however, there is a growing body of work indicating that the cooperative functioning of actin and microtubules is a central element for many cellular key processes, including cell division, cell migration, and adhesion. This project aims at investigating how the spatial organization and dynamics of microtubules are controlled by linkages to the actin cytoskeleton; and in turn, how actin structures within the cell are affected by varying MT dynamics.  

Figure 1: TIRF images of dynamic microtubules in a polymerizing actin network. Scale bars: 10um.

For a more profound and quantitative understand of actin-MT crosstalk, we use a simple yet realistic reconstituted model system, developed in our group [Preciado L√≥pez et al., 2014]. MTs are grown from either stabilized seeds or centrosomes in the presence (or absence) of actin networks. Using fluorescence microscopy techniques such as TIRF, we are able to follow the dynamics of individual growing microtubules, as is shown in Figure 1. Due to the control we have in our reconstituted system, we can confront dynamic MTs with different types of actin networks to account for the diversity of cytoskeleton architectures. For example, we have control over density, geometry, and crosslinking of the actin network, as is shown in Figure 2. Coupling between the two cytoskeleton components is introduced in form of transient binding of actin-MT crosslinkers, or by proteins that interact both with actin and MT plus-end-binding proteins.  

Figure 2: Different geometrical and mechanical actin networks, to account for the diverse cellular architectures.