Proteomic analysis of secretagogue-stimulated neutrophils implicates a role for actin and actin-interacting proteins in Rac2-mediated granule exocytosis

Background: neutrophils are abundant leukocytes that play a primary role in defence against pathogens. neutrophils enter sites of infection where they eliminate pathogens via phagocytosis and the release of antimicrobial mediators via degranulation. rho gtpases,particularly rac2,play a key role in neutrophil degranulation. the purpose of this study was to identify rac2-dependent changes in protein abundance in stimulated neutrophils.methods: we performed a proteomic analysis on secretagogue-stimulated bone marrow neutrophils that were isolated from wild-type and rac2-/-mice. protein abundance was analyzed by 2-dimensional sds-page of fluorescently labelled samples which allowed the detection ~3500 proteins.results: we identified 22 proteins that showed significant changes in abundance after secretagogue-stimulation of wild-type neutrophils,which did not occur in neutrophils isolated from rac2-/-mice. as expected,the abundance of several granule proteins was reduced in wild-type cells; this did not occur in rac2-/-neutrophils which confirms the requirement for rac2 in degranulation. we also found changes in abundance of many actin remodelling proteins including coronin-1a,β-actin and the f-actin capping protein,(capz-β). coronin-1a showed elevated levels of several isoforms after stimulation of neutrophils from wild-type,but not from rac2-/-mice. these isoforms were immunoreactive with anti-phospho-threonine antibodies,suggesting that neutrophil stimulation triggers a rac2-dependent kinase cascade that results in the phosphorylation of coronin-1a.conclusion: the control of rac2-mediated degranulation in neutrophils likely functions through actin remodelling via activation of several actin-binding proteins. we found coronin-1a to be a novel downstream effector protein of this pathway that is threonine phosphorylated in response to secretagogue stimulation. © 2011 eitzen et al; licensee biomed central ltd.