Signal relay during chemotaxis

Abstract

The ability of cells to migrate in response to external cues, a process known as chemotaxis, is a fundamental phenomenon in biology. It is exhibited by a wide variety of cell types in the context of embryogenesis, angiogenesis, inflammation, wound healing and many other complex physiological processes. Here, we discuss the signals that control the directed migration of the social amoebae Dictyostelium discoideum both as single cells and in the context of group migration. This multi-cellular organism has served as an excellent model system to decipher amoeboid-like leukocyte migration and has played a key role in establishing signalling paradigms in the chemotaxis field. We envision that Dictyostelium will continue to bring forward basic knowledge as we seek to understand the mechanisms regulating group cell migration.

Fig. 1

The life cycle of the social amoebae Dictyostelium. (A) Montage of images depicting the developmental program of starving Dictyostelium cells. Cells were plated on non-nutrient agar plates, and pictures were taken at the indicated time after the initiation of starvation. Bar represents 1 mm. (B) Images showing cells migrating in streams during chemotaxis. The image on the left depicts several aggregation centres in streams. The picture on the right presents a higher magnification image of cells migrating in streams to a micro-pipette containing 10 μM cAMP. The white arrow indicates the position of the micro-pipette. Bar represents 1 mm for the right image and 250 μm for the left image.

Fig. 2

The cAMP signal transduction pathway in Dictyostelium. (A) Cartoon representing the cascade of events leading to the activation of ACA. (B) Cartoon depicting the cellular distribution of various signal transduction components during chemotaxis. Actual images of cells expressing CRAC-GFP or ACA-YFP are presented in the last two panels. See text for details.