Abstract
Author SummaryMotile cells have evolved complex regulatory networks to respond to environmental cues and change their direction of movement appropriately. In this process, an arsenal of receptor-coupled small G-proteins acts as a cellular compass to dynamically polarize the leading edge and regulate the motility response. However, the precise mechanism of action of these G-proteins in controlling bacteria movement on solid surfaces has remained an enigma. We investigate this process in Gram negative Myxococcus xanthus cells. Surprisingly, we find that the Ras-like small G-protein MglA polarizes the cell by accumulating at the leading cell pole in its active GTP-bound form. This localization is dependent on MglB, a GTPase-activating protein that converts MglA to its inactive form specifically at the opposite, lagging cell pole. Furthermore, we show that a receptor-coupled signal transduction cascade can activate re-localization of MglA and MglB at opposite poles in a synchronous manner, resulting in inversion of the polarity axis and cell movement in the opposite direction. Thus, a simple, eukaryote-like signaling module also governs dynamic polarity mechanisms in bacteria, demonstrating broader conservation of these signaling systems than initially suspected.
Highlights
In living cells, environmental changes and cell-cell regulations require transient cellular processes relying on the ability of the cells to regulate their underlying ultrastructures dynamically
The precise mechanism of action of these G-proteins in controlling bacteria movement on solid surfaces has remained an enigma. We investigate this process in Gram negative Myxococcus xanthus cells
We show that a receptor-coupled signal transduction cascade can activate re-localization of MglA and MglB at opposite poles in a synchronous manner, resulting in inversion of the polarity axis and cell movement in the opposite direction
Summary
Environmental changes and cell-cell regulations require transient cellular processes relying on the ability of the cells to regulate their underlying ultrastructures dynamically. The cells use a directional sensing system as a compass to favor the formation of pseudopodia towards or away from a source of chemoattractrant or repellent [1]. In this process, the cell adopts a polarized morphology, to define a front and a rear to coordinate actin polymerization at the leading edge with contractile forces generated by myosin motors at the rear. In leukocytes, or in the amoeba Dictyostelium discoidum, polarization is achieved by a complex interplay of multiple small GTP-binding proteins at the front and the rear involving Ras, Rac, Cdc, and Rho (see [2] for a detailed review of these regulations)
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