Stretching and imaging individual proteins on live cells using atomic force microscopy.

Alsteens, David [UCL] Dufrêne, Yves [UCL]

Unraveling the structure–function relationships of cell surface proteins is a major challenge in current cell biology. Two specific questions that are still largely unanswered are (1) how do cell surface proteins respond to mechanical force in relation to function, and (2) how do they dynamically assemble into nanodomains in response to environmental stimuli? In the past years, atomic force microscopy (AFM) has offered unprecedented possibilities for probing the mechanical properties and spatial organization of single proteins on live cells, providing new insight into the highly sophisticated functions of the cell surface. In this chapter, we survey recent progress made in understanding the elasticity, clustering, and functions of yeast cell surface proteins, owing to the integration of the modern tools of molecular genetics (protein design in live cells), with a powerful set of AFM techniques (live cell imaging, single-molecule manipulation, and localization). While we focus on membrane sensors (Saccharomyces cerevisiae) and on cell adhesion proteins (Candida albicans), our methodology and findings should be useful to understand the behavior and function of surface proteins from virtually all cell types.