Cell front supports the back

Chemoattractants cause neutrophils to polarize by triggering competing signaling pathways that promote “frontness” and “backness” at opposite poles of the cell. On page 437, Van Keymeulen et al. report that the two responses are not independent. Instead, frontness signals do double duty by reinforcing backness on the cell's other side.

The chemoattractant fMLP activates receptors that stimulate two different G proteins, Gi and G12/G13. At the front of the neutrophil, Gi increases PIP3 accumulation and turns on Rac and CDC42, causing actin polymers to form a pseudopod. G12/13 stimulates RhoA activity, which causes the back of the cell to contract. The two responses exclude each other locally to produce a single front and a single back, rather than multiple “frontlets” and “backlets” scattered over the cell surface.

Van Keymeulen et al....