Tumor suppressor PTEN is a physiologic suppressor of chemoattractant-mediated neutrophil functions

Abstract

The recruitment and activation of neutrophils at infected tissues is essential for host defense against invading microorganisms. However, excessive neutrophil recruitment or activation can also damage the surrounding tissues and cause unwanted inflammation. Hence, the responsiveness of neutrophils needs to be tightly regulated. In this study, we have investigated the functional role of tumor suppressor PTEN in neutrophils by using a mouse line in which PTEN is disrupted only in myeloid-derived cells. Chemoattractant-stimulated PTEN ؊/؊ neutrophils displayed significantly higher Akt phosphorylation and actin polymerization. A larger fraction of these neutrophils displayed membrane ruffles in response to chemoattractant stimulation. In addition, chemoattractant-induced transwell migration and superoxide production were also augmented. Single-cell chemotaxis assays showed that PTEN ؊/؊ neutrophils have a small (yet statistically significant) defect in directionality. However, these neutrophils also showed an increase in cell speed. As a result, overall chemotaxis, which depends on speed and directionality, was not affected. Consistent with the increased responsivenessof PTEN ؊/؊ neutrophils, the in vivo recruitment of these cells to the inflamed peritoneal cavity was significantly enhanced. Thus, as a physiologic-negative regulator, PTEN should be a promising therapeutic target for modulating neutrophil functions in various infectious and inflammatory dis- IntroductionNeutrophils are the most abundant cell type among circulating white blood cells. The recruitment and activation of neutrophils are important components of the innate immune system. In response to inflammatory stimuli, neutrophils migrate from the blood to infected tissues, where they protect their host by engulfing, killing, and digesting invading bacterial and fungal pathogens. Conversely, excessive neutrophil accumulation or hyperresponsiveness of neutrophils can also be detrimental to the system. The toxic reactive oxygen species and granule enzymes (eg, proteases) released by neutrophils can damage surrounding tissues and cause unwanted and exaggerated tissue inflammation. Hence, the response of neutrophils to inflammatory stimuli needs to be well controlled.Neutrophils get recruited to the site of infection by responding to a variety of chemokines, leukotrienes, complement peptides, and some chemicals released by bacteria directly, such as peptides bearing the N-formyl group (formyl-peptides). 1-3 All these responses are mediated by heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins)-coupled receptors (GPCRs). One essential downstream target of GPCRs is PtdIns(3,4,5)P3, an inositol phospholipid which has been implicated in a variety of neutrophil functions such as polarization, chemotaxis, and superoxide generation. [4][5][6] PtdIns(3,4,5)P3 exerts its function by mediating protein translocation via pleckstrin homology (PH) domains on the protein. 7,8 This membrane translocation is crucial for these proteins to fulfill the...

Regulation of innate immunity by inositol 1,3,4,5-tetrakisphosphate

“…Neutrophils depleted of PTEN, a phosphatidylinositol 3'-phosphatase that negatively regulates Akt activity, live much longer than wild-type neutrophils. 30,31 These results are consistent with previous reports that neutrophil apoptosis is enhanced in PI3Kγ deficient mice, where Akt activity is reduced. 26,32 However, unexpectedly, we observed accelerated apoptotic death in InsP3KB null neutrophils, in which Akt phosphorylation and activation was significantly enhanced.…”

Small-molecule screen identifies reactive oxygen species as key regulators of neutrophil chemotaxis

“…Human blood neutrophil purification, murine bone marrow neutrophil purification, quantification of F-actin levels by phalloidin labeling, measurement of superoxide production by luminol chemiluminescence, micropipette chemotaxis, and transwell migration assays were performed as described previously (25)(26)(27). Peripheral blood was obtained from a human CGD patient and healthy volunteer, with informed consent.…”

“…Peritonitis was induced as previously described (26). Neutrophils isolated from WT and CGD mice were labeled with intracellular fluorescent dye CFSE (final concentration, 1 μM; Molecular Probes) or 5-(and 6-) chloromethyl SNARF-1 acetate (final concentration, 1 μM; Molecular Probes) at 37°C for 10 min.…”

Metastasis-associated Protein 1/Histone Deacetylase 4-Nucleosome Remodeling and Deacetylase Complex Regulates Phosphatase and Tensin Homolog Gene Expression and Function

“…In mammalian cells, localized PtdIns (3, 4, 5), P3 production, and PI3K activity control polarization and migration during chemotactic movement (47). Phosphatidylinositol-3,4,5-triphosphate also provides a docking site for regulators and effectors of the small GTPase Arf6, which regulates actin remodeling (48).…”