We are interested in two major overlapping cell-biological processes: chemotaxis and macropinocytosis. Chemotaxing cells move by extending pseudopods or blebs, which they use to gain traction from their surroundings, and so pull their body forward. They can be guided by attractive chemicals in the environment, so that a neutrophil, for instance, can move to a site of infection or an amoeba can track its bacterial food. In macropinocytosis, cells also produce extensions of their plasma membrane but these are shaped as ruffles or cups, and eventually close, taking a vesicle containing a droplet of medium into the cell. This ingestion allows an immune cell to sample antigens from the medium, or an amoeba to gain nutrients.
Both chemotaxis and phagocytosis are ancient processes, probably dating from primitive, phagotrophic cells, and both use the actin cytoskeleton and cortex to produce projections of the plasma membrane. Both are organised by signalling events at the plasma membrane, which control the location and shape of the projection formed. Small G-proteins and phosphoinositides are prominent in this signalling, and their dynamics are such as to produce discrete, ‘activated’ patches of membrane where actin polymerisation occurs.
Because chemotaxis and macropinocytosis are complicated, conserved processes, yet poorly understood, we use a powerful model system – Dictyostelium amoebae – to study them.
We also have an interest in polyketide signalling and sex determination in Dictyostelium.