Proteinase 3 mRNA expression is induced in monocytes but not in neutrophils of patients with cystic fibrosis

AbstractProteinase 3 (PR3), a serine proteinase which can degrade lung tissue, is present in the cystic fibrosis (CF) sputum. In the present study, PR3 protein and mRNA expression was determined in circulating neutrophils and monocytes. CF neutrophils contained similar PR3 concentrations as healthy controls and poorly expressed PR3 mRNA. In contrast, CF monocytes showed significantly higher PR3 concentrations than controls, together with an upregulation of PR3 mRNA expression especially during pulmonary exacerbation. Interestingly, antibiotic treatment fully abrogated PR3 mRNA expression and decreased PR3 protein in monocytes. Our findings highlight a potential role of monocyte-derived PR3 in CF-associated airway inflammation

Ubiquitin-mediated proteasomal degradation in normal and malignant hematopoiesis.

International audienceUnderstanding the molecular mechanisms controlling normal hematopoietic differentiation is critical to develop new treatments for blood diseases and to manipulate stem cells. Despite the identification of many players in hematopoiesis, the molecular mechanisms controlling hematopoietic differentiation remain poorly understood. Due to a number of recent findings, the targeting of regulators of hematopoiesis to proteasomal degradation might be an important step in control of this developmental program

Shaping Striated Muscles with Ubiquitin Proteasome System in Health and Disease

International audienceFor long-lived contractile cells, such as striated muscle cells, maintaining proteome integrity is a challenging task. These cells require hundreds of components that must be properly synthesized, folded, and incorporated into the basic contractile unit, the sarcomere. Muscle protein quality control in cells is mainly guaranteed by the ubiquitin-proteasome system (UPS), the lysosome-autophagy system, and various molecular chaperones. Recent studies establish the concept of dedicated UPS in the regulation of sarcomere assembly during development and in adult life to maintain the intricate and interwoven organization of protein complexes in muscle. Failure of sarcomere protein quality control often represents the basis of severe myopathies and cardiomyopathies in human, further highlighting its importance in producing and maintaining the contractile machinery of muscle cells in shape

Cullin 5-RING E3 ubiquitin ligases, new therapeutic targets?

International audienceUbiquitylation is a reversible post-translational modification of proteins that controls a myriad of functions and cellular processes. It occurs through the sequential action of three distinct enzymes. E3 ubiquitin ligases (E3s) play the role of conductors of the ubiquitylation pathway making them attractive therapeutic targets. This review is dedicated to the largest family of multimeric E3s, the Cullin-RING E3 (CRL) family and more specifically to cullin 5 based CRLs that remains poorly characterized

Myeloblastin is an Myb target gene: mechanisms of regulation in myeloid leukemia cells growth-arrested by retinoic acid

International audienceA pivotal role has been assigned to Myb in the control of myeloid cell growth. Although Myb is a target of retinoic acid, little is known about the mechanisms by which it may contribute to induced growth arrest in leukemia cells. Indeed, few Myb target genes are known to be linked to proliferation. Myeloblastin is involved in the control of proliferation in myeloid leukemia cells. It is expressed early during hematopoiesis and is a granulocyte colony-stimulating factor-responsive gene. Myeloblastin can confer factor-independent growth to hematopoietic cells, an early step in leukemia transformation. The myeloblastin promoter contains PU.1, C/EBP, and Myb binding sites, each of which are critical for constitutive expression in myeloid cells. Inhibition of myeloblastin expression in leukemia cells growth-arrested by retinoic acid is demonstrated to depend on Myb down-regulation. Myb is shown to induce myeloblastin expression and abolish its down-regulation by retinoic acid. Altogether, the data offer a clue as to how a myeloid-specific transcriptional machinery can be accessible to regulation by retinoic acid and point to myeloblastin as a novel target of Myb. This link between Myb and myeloblastin suggests a previously nonidentified Myb pathway through which growth arrest is induced by retinoic acid in myeloid leukemia cells

The E3 Ubiquitin Ligase Asb2α in T Helper 2 Cells Negatively Regulates Antitumor Immunity in Colorectal Cancer

International audienceThe escape of cancer cells from host immunosurveillance involves a shift in immune responses, including an imbalance in Th1 and Th2 cells. A Th1-dominated immune response predicts positive outcomes in colorectal cancer. The E3 ubiquitin ligase, Asb2α, is expressed in Th2 cells, but its roles in T-cell maturation and cancer are unclear. We provide evidence that the Th2 master regulator, Gata3, induces Asb2 Loss of Asb2 did not affect Th differentiation ex vivo, but reduced IL4 production from Th2 cells. We found that high ASB2 expression was associated with poor outcome in colorectal cancer. Loss of Asb2 from hematopoietic cells promoted a Th1 response and attenuated colitis-associated tumorigenesis in mice. Diminished Th2 function correlated with increased IFNγ production and an enhanced type 1 antitumor immune response in Asb2-deficient mice. Our work suggests that Asb2α promotes a Th2 phenotype in vivo, which in turn is associated with tumor progression in a mouse model of colitis

ASB-2 Inhibits Growth and Promotes Commitment in Myeloid Leukemia Cells*

International audienceIn acute promyelocytic leukemia (APL) cells harboringthe promyelocytic leukemia retinoic acid receptor (PML-RAR) chimeric protein, retinoic acid (RA)-induceddifferentiation is triggered through a PML-RARsignaling resulting in activation of critical target genes.Induced differentiation of APL cells is always precededby withdrawal from the cell cycle and commitmentevents leading to terminal differentiation. Here we haveidentified the human ankyrin repeat-containing proteinwith a suppressor of cytokine signaling box-2 (ASB-2)cDNA, as a novel RA-induced gene in APL cells. PMLRAR strongly enhanced RA-induced ASB-2 mRNA expression.In myeloid leukemia cells, ASB-2 expressioninduced growth inhibition and chromatin condensationrecapitulating early events critical to RA-induced differentiationof APL cells

Myeloblastin is a granulocyte colony-stimulating factor-responsive gene conferring factor-independent growth to hematopoietic cells

Hematopoiesis depends on a pool of quiescent hematopoietic stem/progenitor cells. When exposed to specific cytokines, a portion of these cells enters the cell cycle to generate an amplified progeny. Myeloblastin (MBN) initially was described as involved in proliferation of human leukemia cells. The granulocyte colony-stimulating factor (G-CSF), which stimulates the proliferation of granulocytic precursors, up-regulates MBN expression. Here we show that constitutive overexpression of MBN confers factor-independent growth to murine bone marrow-derived Ba/F3/G-CSFR cells. Our results point to MBN as a G-CSF responsive gene critical to factor-independent growth and indicate that expression of the G-CSF receptor is a prerequisite to this process. A 91-bp MBN promoter region containing PU.1, C/EBP, and c-Myb binding sites is responsive to G-CSF treatment. Although PU.1, C/EBP, and c-Myb transcription factors all were critical for expression of MBN, its up-regulation by G-CSF was associated mainly with PU.1. These findings suggest that MBN is an important target of PU.1 and a key protease for factor-independent growth of hematopoietic cells

ASB2α regulates migration of immature dendritic cells

International audienceThe actin-binding protein filamins (FLNs) are major organizers of the actin cytoskeleton. They control the elasticity and stiffness of the actin network and provide connections with the extracellular microenvironment by anchoring transmembrane receptors to the actin filaments. Although numerous studies have revealed the importance of FLN levels, relatively little is known about the regulation of its stability in physiological relevant settings. Here, we show that the ASB2α cullin 5-ring E3 ubiquitin ligase is highly expressed in immature dendritic cells (DCs) and is down-regulated after DC maturation. We further demonstrate that FLNs are substrates of ASB2α in immature DCs and therefore are not stably expressed in these cells, whereas they exhibit high levels of expression in mature DCs. Using ASB2 conditional knockout mice, we show that ASB2α is a critical regulator of cell spreading and podosome rosette formation in immature DCs. Furthermore, we show that ASB2(-/-) immature DCs exhibit reduced matrix-degrading function leading to defective migration. Altogether, our results point to ASB2α and FLNs as newcomers in DC biology

Substrates of the ASB2α E3 ubiquitin ligase in dendritic cells

International audienc