Neutrophil attachment via Mac-1 ( α _M β ₂ ; CD11b/CD18; CR3) integrins induces PAD4 deimination of profilin and histone H3

Abstract

Neutrophil adhesion to endothelia, entry into tissues and chemotaxis constitute essential steps in the immune response to infections that drive inflammation. Neutrophils bind to other cells and migrate via adhesion receptors, notably the α M β 2 integrin dimer (also called Mac-1, CR3 or CD11b/CD18). Here, the response of neutrophils to integrin engagement was examined by monitoring the activity of peptidylarginine deiminase 4 (PAD4). Histone H3 deimination was strongly stimulated by manganese, an integrin-activating divalent cation, even in the absence of additional inflammatory stimuli. Manganese-induced cell attachment resulted in neutrophil swarm formation that paralleled histone deimination, whereas antibodies that impair integrin binding prevented both cell adhesion and histone deimination. Manganese treatment led to putative deimination of profilin, a protein that functions as an actin-organizing hub, as detected by two-dimensional gel electrophoresis and citrulline immunoblotting. Cl-amidine, a covalent inhibitor of PAD4, and GSK484, a specific PAD4 inhibitor, blocked profilin deimination. Neutrophil migration toward leukotriene B4 and toward synovial fluid from a rheumatoid arthritis patient were inhibited by chloramidine, thus supporting the contribution of deimination to chemotaxis. The data, based on a simplified system for integrin activation, imply a mechanism whereby integrin attachment coordinates neutrophil responses to inflammation and orchestrates deimination of nuclear and cytoskeletal proteins. This article is part of the Theo Murphy meeting issue ‘The virtues and vices of protein citrullination’.

Citrullination: new tricks for an old mod

“…Increased understanding of the neutrophil response to bacterial infection may allow improved methods of combating bacteremia in patients while preventing the deleterious consequences of sepsis. Additionally, a study by Neeli & Radic suggests a new mechanism of PADI4 activation through integrin-mediated neutrophil attachment and provides supporting evidence for a role of citrullination in neutrophil chemotaxis [ 20 ]. The notion that PADI4 is involved in neutrophil chemotaxis is also supported by data presented by Van Bruggen et al [ 11 ] , where it is reported that chemotactic gene expression is reduced in the hearts of mice deficient for neutrophil PADI4 [ 11 ], although the mechanism through which this is mediated remains to be determined.…”