GMCSF activates NF-κB via direct interaction of the GMCSF receptor with IκB kinase β

Abstract

Granulocyte-macrophage colony-stimulating factor (GMCSF) has a central role in proliferation and differentiation of hematopoetic cells. Furthermore, it influences the proliferation and migration of endothelial cells. GMCSF elicits these functions by activating a receptor consisting of a ligand-specific ␣-chain and a ␤-chain, which is common for GMCSF, interleukin-3 (IL-3), and IL-5. It is known that various signaling molecules such as Janus kinase 2 or transcription factors of the signal transducer and activator of transcription (STAT) family bind to the common ␤-chain and initiate signaling cascades. However, ␣-chain-specific signal transduction adapters have to be postulated given that IL-3, IL-5, and GMCSF induce partly distinct biologic responses. Using a yeast 2-hybrid system, we identified the ␣-chain of the GMCSF receptor (GMR␣) as putative interaction partner of IB kinase ␤, one of the central signaling kinases activating the transcription factor nuclear factor-B (NF-B). Using endogenous protein levels of endothelial cell extracts, we could verify the interaction by coimmunoprecipitation experi- IntroductionGranulocyte-macrophage colony-stimulating factor (GMCSF) is a cytokine that was initially described by its ability to induce colonies of granulocytes and macrophages from myeloid progenitor cells. It is involved in proliferation, maturation, and differentiation of these cells and acts via specific receptors on the cell surface. [1][2][3] The GMCSF receptor (GMR) belongs to the class 1 subgroup of the cytokine receptor superfamily and is not only expressed on cells of the granulocyte-macrophage lineage but also on endothelial cells, where it was postulated to have a role in proliferation and migration. 4,5 It is composed of 2 glycoprotein subunits: a 60-to 80-kDa ␣-chain, which by itself exhibits only low-affinity binding of the ligand, and a 120-to 140-kDa ␤-chain, which does not bind GMCSF itself but is essential for high-affinity binding in conjunction with the ␣-chain. [6][7][8] Recent data indicate that 2 ␤-chains associate with 1 or 2 ␣-chains 9,10 and that this ternary GMCSF receptor complex is already preformed in the absence of ligand. 11 While the ␣-chain is specific for GMCSF, the ␤-chain is common for the receptors of GMCSF, interleukin-3 (IL-3), and IL-5, which explains some of the overlapping effects of these 3 cytokines. However, an important contribution of the ␣-chains of these receptors to the intracellular signaling was postulated, and some important differences have been reported for the effects of IL-3, IL-5, and GMCSF. 1,3,[12][13][14][15][16] For all 3 receptors the ␣-chains exhibit rather short cytoplasmic domains as compared with the ␤-chain, which made it difficult to identify signaling partners for the ligand-specific ␣-chains. Recently, an adapter molecule was characterized as interaction partner of the IL-5 receptor ␣-chain, 17 and it could be shown that it is essential for IL-5-mediated signaling to the Sox4 transcription factor, proving the important role of the ligand-s...

Bcl3 prevents acute inflammatory lung injury in mice by restraining emergency granulopoiesis

“…Moreover, we did not observe accumulation of Bcl3 transcripts following GM-CSF stimulation of myeloid progenitors. As the GM-CSF receptor has been reported to a be a strong activator of NF-κB but not STAT3 (48,49), our data collectively support a model in which STAT3 activation is required to drive Bcl3 expression in myeloid progenitors. Interestingly, the ability of IL-6 to stimulate Bcl3 transcript accumulation in myeloid progenitors raises the possibility that this cytokine could play a role in regulating emergency granulopoiesis following lung ischemia reperfusion injury (50).…”

α-Catulin, a Rho signalling component, can regulate NF-κB through binding to IKK-β, and confers resistance to apoptosis

“…Screening of a human liver cDNA library yielded B5.8 million transformants, of which 92 grew on selection plates. Novel interactions included the granulocyte macrophage colony-stimulating receptor a chain, and a protein termed IKIP (Ebner et al, 2003;HoferWarbinek et al, 2004). Eight clones contained different C-terminal parts of a-catulin (CTNNAL1).…”

Thrombin, TNF-α, and LPS exert overlapping but nonidentical effects on gene expression in endothelial cells and vascular smooth muscle cells

“…Whereas agonist-specific differences in cell signaling argue against a simple on-off mechanism of endothelial cell activation, the overlap in expression patterns points to the importance (1), and granulocyte-macrophage colony-stimulating factor (27) have each been shown to activate NF-B; IL-6 (48), IL-10 (16), platelet-activating factor (25), leptin (60), oxidized phospholipids (66), VEGF (9), and FGF-2 (24) are coupled to STAT-3; and hypoxia (39), LPS, high glucose (32), insulin (32), oxidized phospholipids (34), VEGF (40), and hepatocyte growth factor (22) have all been reported to induce Egr-1 in endothelial cells. The above studies were carried out using varying types of endothelial cells and assay systems.…”