Mini Review: Specificity in cytokine signal transduction: lessons learned from the IL-3:IL-5:GM-CSF receptor family

Cytokines mediate the transduction of proliferative, differentiation and survival signals in the hematopoietic system. Although the cytokine family is large and diverse, many different cytokines display broadly overlapping functions. This can be explained by the fact that cytokine receptors often share multiple subunits. Specificity in signal transduction can however be achieved through several mechanisms. This review focuses on how signal specificity can be achieved within the IL-3, IL-5 and GM-CSF receptor family. This is discussed in terms of receptor expression, recent advances in our understanding of intracellular signalling components, and analysis of null mutant knock-out mice

Activation of RhoA and ROCK Are Essential for Detachment of Migrating Leukocytesh

Detachment of the rear of the cell from its substratum is an important aspect of locomotion. The signaling routes involved in this adhesive release are largely unknown. One of the few candidate proteins to play a role is RhoA, because activation of RhoA in many cell types leads to contraction, a mechanism probably involved in detachment. To study the role of RhoA in detachment regulation, we analyzed several subsets of expert migratory leukocytes by video microscopy. In contrast to fast-migrating neutrophils, eosinophils do not detach the rear of the cell unless stimulated with serum. When measuring the amount of active RhoA, with the use of a GSTRhotekin pulldown assay, we found that serum is an excellent activator of RhoA in granulocytes. Inhibition of RhoA or one of Rhos target proteins, the kinase ROCK, in neutrophils leads to the phenotype seen in eosinophils: the rear of the cell is firmly attached to the substratum, whereas the cell body is highly motile. ROCK-inhibition leads to impaired migration of granulocytes in filters, on glass, and through endothelial monolayers. Also, the ROCK signaling pathway is involved in changes of integrin-mediated adhesion. Eosinophil transduction by a tat-fusion construct containing active RhoA resulted in detachment stimulation in the presence of chemoattractant. From these results we conclude that activation of the RhoA-ROCK pathway is essential for detachment of migratory leukocytes

Regulation of Proliferation, Differentiation and Survival by the IL-3/IL-5/GM-CSF Receptor Family

The receptors for the Il-3/IL-5/GM-CSF cytokine family are composed of a heterodimeric com-plex of a cytokine-specific a chain and a common ß chain (ßc). Binding of IL-3/IL-5/GM-CSF to their respective receptors rapidly induces activation of multiple intracellular signalling pathways, including the Ras-Raf-ERK, the JAK/STAT, the phosphatidylinositol 3-kinase PKB, and the JNK/SAPK and p38 signalling pathways. This re-view focuses on recent advancements in understanding how these different signalling pathways are activated by IL-3/IL-5/GM-CSF receptors, and how the individual pathways contribute to the pleiotropic effects of IL-3/IL-5/ GM-CSF on their target cells, including proliferation, differentiation, survival, and effector functions

The effect of C1-esterase inhibitor on systemic inflammation in trauma patients with a femur fracture - The CAESAR study: study protocol for a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Systemic inflammation in response to a femur fracture and the additional fixation is associated with inflammatory complications, such as acute respiratory distress syndrome and multiple organ dysfunction syndrome. The injury itself, but also the additional procedure of femoral fixation induces a release of pro-inflammatory cytokines such as interleukin-6. This results in an aggravation of the initial systemic inflammatory response, and can cause an increased risk for the development of inflammatory complications. Recent studies have shown that administration of the serum protein C1-esterase inhibitor can significantly reduce the release of circulating pro-inflammatory cytokines in response to acute systemic inflammation.</p> <p>Objective</p> <p>Attenuation of the surgery-induced additional systemic inflammatory response by perioperative treatment with C1-esterase inhibitor of trauma patients with a femur fracture.</p> <p>Methods</p> <p>The study is designed as a double-blind randomized placebo-controlled trial. Trauma patients with a femur fracture, Injury Severity Score ≥ 18 and age 18-80 years are included after obtaining informed consent. They are randomized for administration of 200 U/kg C1-esterase inhibitor intravenously or placebo (saline 0.9%) just before the start of the procedure of femoral fixation. The primary endpoint of the study is Δ interleukin-6, measured at t = 0, just before start of the femur fixation surgery and administration of C1-esterase inhibitor, and t = 6, 6 hours after administration of C1-esterase inhibitor and the femur fixation.</p> <p>Conclusion</p> <p>This study intents to identify C1-esterase inhibitor as a safe and potent anti-inflammatory agent, that is capable of suppressing systemic inflammation in trauma patients. This might facilitate early total care procedures by lowering the risk of inflammation in response to the surgical intervention. This could result in increased functional outcomes and reduced health care related costs.</p> <p>Trial registration</p> <p>clinicaltrials.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT01275976">NCT01275976</a> (January 12th 2011)</p

Analysis of Signal Transduction Pathways Regulating Cytokine-Mediated Fc Receptor Activation on Human Eosinophils

Igs can be potent stimulants of eosinophil activation since interaction with IgA or IgG-coated particles can lead to eosinophil degranulation. We have investigated the comparative roles of mitogen-activated protein (MAP) kinases (MAPKs; ERK1/2 and p38) and phosphatidylinositol-3 kinase (PI3K) in the priming and regulation of Fc receptor functioning on human eosinophils utilizing a MAPK kinase (MEK) inhibitor (PD98059), a p38 inhibitor SB203580, and the widely used PI3K inhibitors wortmannin and LY294002. We demonstrate that priming of human eosinophils with Th2-derived cytokines, IL-4 and IL-5, differentially activate phosphotyrosine-associated PI3K and ERK and p38 MAP kinases. This activation can be inhibited by pre-incubation with wortmannin or LY294002, PD98059, and SB203580, respectively. Analysis of the effects of the inhibitors on rosette formation between human eosinophils and IgA- or IgG-coated beads revealed that activation of MEK was not required for IgA binding after priming with IL-4 or IL-5. However, inhibition of MEK did inhibit IL-5-primed binding of IgG-beads. The rosette formation of primed eosinophils with IgA-beads could be completely inhibited by wortmannin and LY294002 treatment, demonstrating a critical role for PI3K. Interestingly, inhibition of the p38 pathway also resulted in a complete blockade of IgA rosette formation. This work demonstrates regulatory control by inside-out signaling of Fc receptors by various cytokines on human eosinophils. Thus in vivo the local production of Th2-derived cytokines will regulate the effector functions of Fc receptors

Cytokine-induced inside-out activation of FcaR (CD89) is mediated by a single serine residue (S263) in the intracellular domain of the receptor

Fc receptors play an important role in leukocyte activation and the modulation of ligand binding ("activation") is a criti-cal point of regulation. Previous studies demonstrated that the Fc receptor for IgA (FcaRI/CD89) is regulated by cytokine stimulation, switching it to a high-binding state. To investigate the mechanism by which cytokine-induced signal transduc-tion pathways result in FcaRI activation, cell lines expressing various receptor mu-tants were generated. Binding studies indicated that truncation of the C-termi- nus of the FcaRI resulted in constitutive IgA binding, removing the need for cyto-kine stimulation. Furthermore, mutagen-esis of a single C-terminal serine residue (S263) to alanine (S>A) (single-letter amino acid codes) also resulted in consti-tutive IgA binding, whereas a serine to aspartate (S>D) mutation was no longer functional. The role of S263 might be in regulating the interaction with the cy-toskeleton, because disruption of the cy-toskeleton results in reduced IgA binding to both FcaRwt and FcaR_S>A. In addi- tion, overexpression of a membrane-targeted intracellular domain of FcaR, and the introduction of cell-permeable CD89 fusion proteins blocked IgA bind-ing, implying a competition for endoge-nous proteins. The proposal is made that Fc receptors are activated by cytokines via an inside-out mechanism converging at the cytoplasmic tail of these receptors