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Amoeboid cells that migrate through our tissues, such as the class of white blood cells known as neutrophils, often do so in a directed manner, triggered, for instance, by chemical signals released by pathogens such as bacteria. Directed migration in response to a chemical stimulus is known as
RAC is responsible for protrusion as well as attachment and thus, dominates at the leading edge while Rho will dominate at the trailing edge because it is used for traction. These three steps, protrusion, attachment and traction, are important for cell movement.
During the process of chemotaxis, the binding of a chemoattractant will lead to the activation of both Rac and Rho at the leading edge and trailing edge, respectively.
When Rac is activated, it will work by promoting the actin polymerization, which will result in the formation or production of lamellipodia, which is important for whole cell locomotion. This actin polymerization will lead to the protrusion, which will allow directional cell movement, as actin filaments will extend outward in the moving direction. In this case, it is towards the chemoattractant.
When Rho is activated, it will work by facilitating stress fiber formation, and better contraction through myosin. This is required for the traction step taking place during cell movement. It occurs at the trailing edge to facilitate directional cell movement due to resulting in actin-myosin contractions, therefore moving the trailing edge of the cell in the forward direction.
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