High resolution

Module 11: Figure neutrophil chemotactic signalling



Neutrophil chemotactic signalling mechanisms.

Chemotaxis of neutrophils in response to a gradient of a chemoattractant such as fMet-Leu-Phe (fMLP) that elicits different signalling mechanism at the front and back. The large yellow arrow encloses those signalling components that may function as the compass responsible for setting up the polarity that drives directed cell movement. At the front, fMLP acts through guanine nucleotide exchange factors (GEFs) to activate both Cdc42 and Rac. The activated Cdc42 and Rac initiates an amplification loop by stimulating phosphoinositide 3-kinase (PI 3-K) that establishes a high level of the lipid second messenger PtdIns3,4,5P3 (PIP3) in the front of the cell. The localized PIP3 together with Cdc42 and Rac, then act together to assemble actin in the pseudopod. At the rear of the cell, the fMLP receptor activates Rho that then stimulates the Rho kinase (ROK) to induce contraction of the uropod.