The β Common Cytokine Receptor Family Reveals New Functional Paradigms From Structural Complexities.

Cytokines are small proteins that are critical for controlling the growth and activity of hematopoietic cells by binding to cell surface receptors and transmitting signals across membranes. The β common (βc) cytokine receptor family, consisting of the granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5 cytokine receptors, is an architype of the heterodimeric cytokine receptor systems. We now know that signaling by cytokine receptors is not always an "all or none" phenomenon.

Accelerated Closure of Diabetic Wounds by Efficient Recruitment of Fibroblasts upon Inhibiting a 14-3-3/ROCK Regulatory Axis.

Chronic non-healing wounds negatively impact quality of life and are a significant financial drain on health systems. The risk of infection that exacerbates comorbidities in patients necessitates regular application of wound care. Understanding the mechanisms underlying impaired wound healing are therefore a key priority to inform effective new-generation treatments.

IgE receptor of mast cells signals mediator release and inflammation via adaptor protein 14-3-3ζ.

Background: Mast cells (MCs) are tissue-resident immune cells that mediate IgE-dependent allergic responses. Downstream of FcεRI, an intricate network of receptor-specific signaling pathways and adaptor proteins govern MC function. The 14-3-3 family of serine-threonine phosphorylation-dependent adapter proteins are known to organize intracellular signaling.

The Amyloid Fibril-Forming β-Sheet Regions of Amyloid β and α-Synuclein Preferentially Interact with the Molecular Chaperone 14-3-3ζ.

14-3-3 proteins are abundant, intramolecular proteins that play a pivotal role in cellular signal transduction by interacting with phosphorylated ligands. In addition, they are molecular chaperones that prevent protein unfolding and aggregation under cellular stress conditions in a similar manner to the unrelated small heat-shock proteins. In vivo, amyloid β (Aβ) and α-synuclein (α-syn) form amyloid fibrils in Alzheimer's and Parkinson's diseases, respectively, a process that is intimately linked to the diseases' progression.

Role of salt bridges in the dimer interface of 14-3-3ζ in dimer dynamics, N-terminal α-helical order, and molecular chaperone activity.

The 14-3-3 family of intracellular proteins are dimeric, multifunctional adaptor proteins that bind to and regulate the activities of many important signaling proteins. The subunits within 14-3-3 dimers are predicted to be stabilized by salt bridges that are largely conserved across the 14-3-3 protein family and allow the different isoforms to form heterodimers. Here, we have examined the contributions of conserved salt-bridging residues in stabilizing the dimeric state of 14-3-3ζ.

Corrigendum: 14-3-3ζ regulates the mitochondrial respiratory reserve linked to platelet phosphatidylserine exposure and procoagulant function.

This corrects the article DOI: 10.1038/ncomms12862.

14-3-3ζ regulates the mitochondrial respiratory reserve linked to platelet phosphatidylserine exposure and procoagulant function.

The 14-3-3 family of adaptor proteins regulate diverse cellular functions including cell proliferation, metabolism, adhesion and apoptosis. Platelets express numerous 14-3-3 isoforms, including 14-3-3ζ, which has previously been implicated in regulating GPIbα function. Here we show an important role for 14-3-3ζ in regulating arterial thrombosis.

A Negative Regulatory Mechanism Involving 14-3-3ζ Limits Signaling Downstream of ROCK to Regulate Tissue Stiffness in Epidermal Homeostasis.

ROCK signaling causes epidermal hyper-proliferation by increasing ECM production, elevating dermal stiffness, and enhancing Fak-mediated mechano-transduction signaling. Elevated dermal stiffness in turn causes ROCK activation, establishing mechano-reciprocity, a positive feedback loop that can promote tumors. We have identified a negative feedback mechanism that limits excessive ROCK signaling during wound healing and is lost in squamous cell carcinomas (SCCs).

Destabilisation of dimeric 14-3-3 proteins as a novel approach to anti-cancer therapeutics.

14-3-3 proteins play a pivotal role in controlling cell proliferation and survival, two commonly dysregulated hallmarks of cancers. 14-3-3 protein expression is enhanced in many human cancers and correlates with more aggressive tumors and poor prognosis, suggesting a role for 14-3-3 proteins in tumorigenesis and/or progression. We showed previously that the dimeric state of 14-3-3 proteins is regulated by the lipid sphingosine, a physiological inducer of apoptosis.

Protein kinase activity of phosphoinositide 3-kinase regulates cytokine-dependent cell survival.

The dual specificity protein/lipid kinase, phosphoinositide 3-kinase (PI3K), promotes growth factor-mediated cell survival and is frequently deregulated in cancer. However, in contrast to canonical lipid-kinase functions, the role of PI3K protein kinase activity in regulating cell survival is unknown. We have employed a novel approach to purify and pharmacologically profile protein kinases from primary human acute myeloid leukemia (AML) cells that phosphorylate serine residues in the cytoplasmic portion of cytokine receptors to promote hemopoietic cell survival.

The GM-CSF receptor family: mechanism of activation and implications for disease.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pluripotent cytokine produced by many cells in the body, which regulates normal and malignant hemopoiesis as well as innate and adaptive immunity. GM-CSF assembles and activates its heterodimeric receptor complex on the surface of myeloid cells, initiating multiple signaling pathways that control key functions such as cell survival, cell proliferation, and functional activation. Understanding the molecular composition of these pathways, the interaction of the various components as well as the kinetics and dose-dependent mechanics of receptor activation provides valuable insights into the function of GM-CSF as well as the related cytokines, interleukin-3 and interleukin-5.

Drosophila 14-3-3ε has a crucial role in anti-microbial peptide secretion and innate immunity.

The secretion of anti-microbial peptides is recognised as an essential step in innate immunity, but there is limited knowledge of the molecular mechanism controlling the release of these effectors from immune response cells. Here, we report that Drosophila 14-3-3ε mutants exhibit reduced survival when infected with either Gram-positive or Gram-negative bacteria, indicating a functional role for 14-3-3ε in innate immunity. In 14-3-3ε mutants, there was a reduced release of the anti-microbial peptide Drosomycin into the haemolymph, which correlated with an accumulation of Drosomycin-containing vesicles near the plasma membrane of cells isolated from immune response tissues.

NMR spectroscopy of 14-3-3ζ reveals a flexible C-terminal extension: differentiation of the chaperone and phosphoserine-binding activities of 14-3-3ζ.

Intracellular 14-3-3 proteins bind to many proteins, via a specific phosphoserine motif, regulating diverse cellular tasks including cell signalling and disease progression. The 14-3-3ζ isoform is a molecular chaperone, preventing the stress-induced aggregation of target proteins in a manner comparable with that of the unrelated sHsps (small heat-shock proteins). 1H-NMR spectroscopy revealed the presence of a flexible and unstructured C-terminal extension, 12 amino acids in length, which protrudes from the domain core of 14-3-3ζ and is similar in structure and length to the C-terminal extension of mammalian sHsps.

Sphingosine and FTY720 directly bind pro-survival 14-3-3 proteins to regulate their function.

The dimeric 14-3-3 protein family protects cells from apoptosis by regulating pro-apoptotic molecules. Conversely, the cationic lipid sphingosine is associated with physiological apoptosis and induces apoptosis in its own right by a largely undefined mechanism. We show here that sphingosine and 14-3-3 interact directly in the control of cell death.

The structure of the GM-CSF receptor complex reveals a distinct mode of cytokine receptor activation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic cytokine that controls the production and function of blood cells, is deregulated in clinical conditions such as rheumatoid arthritis and leukemia, yet offers therapeutic value for other diseases. Its receptors are heterodimers consisting of a ligand-specific alpha subunit and a betac subunit that is shared with the interleukin (IL)-3 and IL-5 receptors. How signaling is initiated remains an enigma.

Sphingosine and ceramide signalling in apoptosis.

The sphingomyelin pathway is activated in response to many apoptotic stimuli leading to the accumulation of breakdown products ceramide and sphingosine. Ceramide has received much attention as an apoptotic second messenger whereas sphingosine has largely been overlooked as a mediator of apoptosis. Recent studies however provide strong clues to a second messenger role for sphingosine and identification of effectors reveal a possible mechanism involved in sphingosine-mediated cell death.

Sphingosine activates protein kinase A type II by a novel cAMP-independent mechanism.

Protein kinase A (PKA) has long been recognized as playing a major role in many regulatory processes in cells through its activation by the ubiquitous second messenger cAMP. We show here a novel mode of activation of PKA type II that is independent of cAMP and is, instead, dependent on sphingosine. PKA type II is specifically activated by sphingosine and its analog, dimethylsphingosine, but not by sphingosine-1-phosphate or other lipids.

The dimeric versus monomeric status of 14-3-3zeta is controlled by phosphorylation of Ser58 at the dimer interface.

The 14-3-3 proteins play a central role in the regulation of cell growth, cycling, and apoptosis by modulating the functional activities of key signaling proteins. Through binding to a phosphoserine motif, 14-3-3 alters target proteins activities by sequestering them, relocalizing them, conformationally altering their functional activity, or by promoting interaction with other proteins. These functions of 14-3-3 are facilitated by, if not dependent on, its dimeric structure.

Molecular assembly of the ternary granulocyte-macrophage colony-stimulating factor receptor complex.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that stimulates the production and functional activity of granulocytes and macrophages, properties that have encouraged its clinical use in bone marrow transplantation and in certain infectious diseases. Despite the importance of GM-CSF in regulating myeloid cell numbers and function, little is known about the exact composition and mechanism of assembly of the GM-CSF receptor complex. We have now produced soluble forms of the GM-CSF receptor alpha chain (sGMRalpha) and beta chain (sbetac) and utilized GM-CSF, the GM-CSF antagonist E21R (Glu21Arg), and the betac-blocking monoclonal antibody BION-1 to define the molecular assembly of the GM-CSF receptor complex.

Endogenous interferon-alpha production by differentiating human monocytes regulates expression and function of the IL-2/IL-4 receptor gamma chain.

In vitro monocyte-derived macrophages (MDMac) and synovial fluid macrophages from inflamed joints differ from monocytes in their responses to interleukin 4 (IL-4). While IL-4 can suppress LPS-induced interleukin beta (IL-beta) and tumour necrosis factor alpha (TNF-alpha) production by monocytes, IL-4 can suppress LPS-induced IL-1 beta, but not TNFalpha production by the more differentiated cells. Recently we reported a correlation between the ability of IL-4 to regulate TNFalpha production by monocytes and the expression of the IL-4 receptor gamma chain or gamma common (gamma c chain).