Regulation of Cytokine Action
Socs3 maintains the specificity of biological responses to cytokine signals during granulocyte and macrophage differentiation
BA Croker, D Metcalf, H Kiu, WS Alexander, AW Roberts in collaboration with LA Mielke, DJ Hilton (Molecular Medicine Division), S Wormald (Bioinformatics Division) Pub ref: 28
The generation of macrophages and neutrophils from haemopoietic progenitor cells requires the integration of cytokine signals to coordinate the proliferation, differentiation and survival of progenitor cells to form mature myeloid cells. Although the cytokines that drive myeloid cell production are well documented, much less is known about how haemopoietic progenitor cells interpret and integrate cytokine signals to form a macrophage or a neutrophil. The magnitude and duration of cytokine receptor activation is likely to influence the decision-making process of the progenitor cell by altering the profile of transcriptional regulators present in the cell during differentiation.
Granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) play key roles in regulating myeloid cell development, and are both negatively regulated by the inducible intracellular protein suppressor of cytokine signalling-3 (Socs3). To determine which elements of cellular responses to cytokines require Socs3, we have examined the differentiative and proliferative capacity of haemopoietic progenitor cells stimulated by G-CSF and IL-6. The differentiation of Socs3-deficient progenitor cells is skewed towards macrophage production in response to G-CSF or IL-6, whereas wild-type progenitor cells produce mainly neutrophils. The proliferative capacity of Socs3-deficient progenitor cells is greatly enhanced in response to G-CSF. Cytokine-induced expression of transcriptional regulators including Cebpb, Ets2, Bcl3, c-Myc, Jun and Fosl2 are differentially regulated in Socs3-deficient cells. Socs3 controls the fate of myeloid progenitor cells after cytokine receptor ligation by regulating STAT3 phosphorylation and gene transcription.
STAT3 activation (green) is enhanced in Socs3-deficient haemopoietic progenitor cells in response to interleukin-6. DNA is stained blue.
Blocking LIF action in the uterus using a PEGylated antagonist: a new contraceptive strategy
CA White, J-G Zhang, D Metcalf, NA Nicola, L Robb in collaboration with WD Fairlie (Structural Biology Division), E Dimitriadis, LA Salamonsen (Prince Henry’s Institute of Medical Research, Clayton), M Baca (MedImmune Inc., Gaithersburg, MD USA) Pub ref: 152
Leukaemia inhibitory factor (LIF) is essential for mouse blastocyst implantation, and also plays a role in human pregnancy. We used a potent LIF antagonist modified by the addition of polyethylene glycol (PEGLA) to completely block blastocyst implantation in mice. PEGLA was administered via three intraperitoneal injections between days 2.5 and 3.5 of pregnancy, just prior to the time of implantation. We showed that PEGLA acts by blocking phosphorylation of LIF’s downstream signalling molecule, STAT3, in uterine luminal epithelial cells, and has no embryo-lethal effects. Our findings showed the potential of PEGLA as a new, non-hormonal contraceptive strategy for women.
Suppressor of Cytokine Signalling 1 (Socs1) is a physiological regulator of the asthma response
C Lee, T Kolesnik, A Chakravorty, W Carter, WS Alexander, S Nicholson in collaboration with J Jones, G Anderson (The University of Melbourne)
We have used an aeroallergen-driven asthma model to investigate the role of Socs1 in regulating T helper type 2 (Th2) cytokine-associated traits implicated in allergic asthma, such as IgE levels, mucin production and eosinophilic inflammation. Following sensitisation and challenge with ovalbumin (OVA), serum IgE levels and infiltrating eosinophils were greatly increased in OVA-treated Socs1-/-Ifnγ-/- mice, indicating that Socs1 is an important regulator of the Th2 response. Eotaxin-1 and Arginase I mRNA levels were also up-regulated in the lungs from OVA-treated Socs1-/-Ifnγ-/- mice, however mRNA for the IL-13-induced mucin, Muc5ac and the acidic mammalian chitinase were not, further suggesting that Socs1 directly regulates IL-4 and/or IL-5, rather than IL-13 responses.
The role of Socs3 in endothelial cells
H Kiu, AW Roberts, WS Alexander
The absence of Socs3 in blood and endothelial cells leads to spontaneous inflammation, but our recent data demonstrate that loss of Socs3 in blood cells alone is not sufficient for disease. This implies that Socs3 is required in non-haemopoietic tissues to prevent spontaneous inflammation. We hypothesise that endothelial cells, which play important roles in inflammatory responses, may require Socs3 for appropriate function. We are currently testing this hypothesis via analysis of inflammation in mice lacking Socs3 specifically in endothelial cells.
Sustained haemopoiesis from blast colony-forming cells
Stem cells were originally recognised following the use of human or mouse marrow grafts to recipients with severely damaged marrow, but these cells are not necessarily involved in sustaining haemopoiesis under basal conditions. Two types of blast colonies form after stimulation by Stem cell factor (SCF)+IL-6 or FH3-ligand (FL)+IL-6. The two sets of blast colony-forming cells (BL CFC) are largely separate but share some overlap. BL CFC are enriched in long-term repopulating fractions (CD34– Flt3– LSK) and multipotential fractions (CD34+ Flt3+ LSK) of the bone marrow, but are most enriched in short-term repopulating fractions (CFUs) (CD34+ Flt3–). The phenotype of immature haemopoietic cells shown by BL CFC is paralleled by their capacity to generate large numbers of granulocyte, granulocyte-macrophage and macrophage progenitors and also to self-generate. These cells have the potential to sustain the long-term production of granulocyte and macrophage populations.