Molecular analysis of the properties of human Arp2/3 complex family members

The actin cytoskeleton is a dynamic polymer system, that provides the driving force and structural support for the physical integrity of cells, and their interactions. It also regulates many essential cellular processes, such as membrane trafficking and cell migration. Not surprisingly, its malfunction results in a wide variety of syndromes and diseases.

Branched actin networks can only be assembled by the Arp2/3 complex, consisting of seven protein subunits.

Activated by nucleation promoting factors (NPFs), Arp2/3 binds to the side of an actin filament to initiate an actin branch and new filament growth.

Arp2/3 has been regarded as a single entity, but in mammals, three of its subunits exist as two isoforms, thus allowing the formation of 8 different complexes. Recent work demonstrates that the 8 human Arp2/3 complexes have unique cellular properties. However, it is unclear why these complexes are so different and whether they have distinct cellular functions.

Using in vitro biochemical assays and single molecule analysis together with sophisticated cell biology approaches, I will determine the molecular basis for the individual properties of the different Arp2/3 complexes.

Observing in vitro reconstituted actin networks, I will perform a detailed analysis of the actin nucleation properties of the 8 Arp2/3 complexes and the impact of different NPFs.

In addition, I will also analyse actin branch disassembly to uncover the molecular basis of actin debranching, which still remains to be established.

To investigate the cellular function of individual Arp2/3 family members, I will generate genome edited cells expressing defined Arp2/3 complexes and examine their lamellipodial actin dynamics and cell migration.

Moreover, by generating Arp2/3 complex specific biosensors, I will map the cellular distribution of individual Arp2/3 complexes. My combined approaches will allow me to understand the molecular and cellular basis of Arp2/3 diversity in humans.