Module 11: Figure neutrophil chemotaxis
Structural organization of neutrophil motility and chemotaxis.
The top view shows a neutrophil moving up a gradient of a chemoattractant such as fMet-Leu-Phe (fMLP). The exploratory pseudopod at the front has an extensive actin meshwork. The actin and myosin II located at the rear enables the uropod to contract to propel the cell forwards. The microtubule-organizing centre (MTOC) aligns the microtubules in the direction of movement and helps to stabilize cell polarity. The side view illustrates how polarity is established by fMLP acting on receptors to promote actin assembly and pseudopod formation at the front and contraction of the uropod at the rear. During movement, integrins attach at the front and detach at the rear. The yellow halo at the front represents a local concentration of ATP released from the cell through hemichannels. The ATP and its hydrolytic product adenosine feedback in an autocrine manner to activate P2Y2 and A3 purinergic receptors that function to amplify the chemotactic response. Information on the standing Ca2+ gradient (see the red shading showing the high level at the back and the low level at the front) and the Ca2+ flickers was taken from Wei et al. (2009).