6-Phosphogluconolactonase is critical for the efficient functioning of the pentose phosphate pathway.

The metabolic networks of microorganisms are remarkably robust to genetic and environmental perturbations. This robustness stems from redundancies such as gene duplications, isoenzymes, alternative metabolic pathways, and also from non-enzymatic reactions. In the oxidative branch of the pentose phosphate pathway (oxPPP), 6-phosphogluconolactone hydrolysis into 6-phosphogluconate is catalysed by 6-phosphogluconolactonase (Pgl) but in the absence of the latter, the oxPPP flux is thought to be maintained by spontaneous hydrolysis.

Acetate is a beneficial nutrient for E. coli at low glycolytic flux.

Acetate, a major by-product of glycolytic metabolism in Escherichia coli and many other microorganisms, has long been considered a toxic waste compound that inhibits microbial growth. This counterproductive auto-inhibition represents a major problem in biotechnology and has puzzled the scientific community for decades. Recent studies have however revealed that acetate is also a co-substrate of glycolytic nutrients and a global regulator of E.

Control and regulation of acetate overflow in .

Overflow metabolism refers to the production of seemingly wasteful by-products by cells during growth on glucose even when oxygen is abundant. Two theories have been proposed to explain acetate overflow in - global control of the central metabolism and local control of the acetate pathway - but neither accounts for all observations. Here, we develop a kinetic model of metabolism that quantitatively accounts for observed behaviours and successfully predicts the response of to new perturbations.

Asb2α-Filamin A Axis Is Essential for Actin Cytoskeleton Remodeling During Heart Development.

Rationale: Heart development involves differentiation of cardiac progenitors and assembly of the contractile sarcomere apparatus of cardiomyocytes. However, little is known about the mechanisms that regulate actin cytoskeleton remodeling during cardiac cell differentiation.

Objective: The Asb2α (Ankyrin repeat-containing protein with a suppressor of cytokine signaling box 2) CRL5 (cullin 5 RING E3 ubiquitin ligase) triggers polyubiquitylation and subsequent degradation by the proteasome of FLNs (filamins).

Substrates of the ASB2α E3 ubiquitin ligase in dendritic cells.

Conventional dendritic cells (cDCs) comprise distinct populations with specialized immune functions that are mediators of innate and adaptive immune responses. Transcriptomic and proteomic approaches have been used so far to identify transcripts and proteins that are differentially expressed in these subsets to understand the respective functions of cDCs subsets. Here, we showed that the Cullin 5-RING E3 ubiquitin ligase (E3) ASB2α, by driving degradation of filamin A (FLNa) and filamin B (FLNb), is responsible for the difference in FLNa and FLNb abundance in the different spleen cDC subsets.

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

Ubiquitylation 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.

Phosphorylation of serine 323 of ASB2α is pivotal for the targeting of filamin A to degradation.

ASB proteins are the specificity subunits of cullin5-RING E3 ubiquitin ligases (CRL5) that play roles in ubiquitin-mediated protein degradation. However, how their activity is regulated remains poorly understood. Here, we unravel a novel mechanism of regulation of a CRL5 through phosphorylation of its specificity subunit ASB2α.

Deciphering the ubiquitin proteome: Limits and advantages of high throughput global affinity purification-mass spectrometry approaches.

Ubiquitination is a posttranslational modification of proteins that involves the covalent attachment of ubiquitin, either as a single moiety or as polymers. This process controls almost every cellular metabolic pathway through a variety of combinations of linkages. Mass spectrometry now allows high throughput approaches for the identification of the thousands of ubiquitinated proteins and of their ubiquitination sites.

Quantitative proteomic analysis to decipher the differential apoptotic response of bortezomib-treated APL cells before and after retinoic acid differentiation reveals involvement of protein toxicity mechanisms.

The ubiquitin-proteasome system allows the targeted degradation of proteins and plays a critical role in the regulation of many cellular processes. Proteasome inhibition is a recent antitumor therapeutic strategy and bortezomib was the first proteasome inhibitor approved for clinical use. In this study, we used the NB4 cell line to investigate the effects of bortezomib toward acute promyelocytic leukemia cells before and after retinoic acid-induced differentiation.

Muscle actin is polyubiquitinylated in vitro and in vivo and targeted for breakdown by the E3 ligase MuRF1.

Muscle atrophy prevails in numerous diseases (cancer cachexia, renal failure, infections, etc.), mainly results from elevated proteolysis, and is accelerated by bed rest. This largely contributes to increased health costs.

Diagnostic value and prognostic significance of plasmatic proteasome level in patients with melanoma.

Plasmatic proteasome (p-proteasome) also called circulating proteasome has recently been described as a tumor marker. We investigated the diagnostic and prognostic accuracies of p-proteasome levels in a melanoma population classified according to the American Joint Committee on Cancer staging system. Using an ELISA test, we measured p-proteasome levels in 90 patients and 40 controls between March 2003 and March 2008.

Proteasome inhibitor-induced apoptosis in acute myeloid leukemia: a correlation with the proteasome status.

The proteasome plays a critical role in the regulation of many cellular processes, including the cell cycle and tumor growth. The proteasome inhibitor bortezomib has recently been approved for the treatment of relapsed and refractory multiple myeloma. In this study, we investigated the induction of apoptosis by proteasome inhibitors in several human acute myeloid leukemia (AML) cell lines and in primary cells from patients.

A label-free quantitative proteomics strategy to identify E3 ubiquitin ligase substrates targeted to proteasome degradation.

The ubiquitin-proteasome system is a central mechanism for controlled proteolysis that regulates numerous cellular processes in eukaryotes. As such, defects in this system can contribute to disease pathogenesis. In this pathway, E3 ubiquitin ligases provide platforms for binding specific substrates, thereby coordinating their ubiquitylation and subsequent degradation by the proteasome.

Affinity purification strategy to capture human endogenous proteasome complexes diversity and to identify proteasome-interacting proteins.

An affinity purification strategy was developed to characterize human proteasome complexes diversity as well as endogenous proteasome-interacting proteins (PIPs). This single step procedure, initially used for 20 S proteasome purification, was adapted to purify all existing physiological proteasome complexes associated to their various regulatory complexes and to their interacting partners. The method was applied to the purification of proteasome complexes and their PIPs from human erythrocytes but can be used to purify proteasomes from any human sample as starting material.

Toward a full characterization of the human 20S proteasome subunits and their isoforms by a combination of proteomic approaches.

The 20S proteasome is a multicatalytic protein complex, present in all eukaryotic cells, that plays a major role in intracellular protein degradation. In mammalian cells, this symmetrical cylindrical complex is composed of two copies each of seven different alpha and beta subunits arranged into four stacked rings (alpha(7)beta(7)beta(7)alpha(7)). Separation by two-dimensional (2D) gel electrophoresis of the human erythrocytes 20S proteasome subunits and mass spectrometry (MS) identification of all the observed spots reveal the presence of multiple isoforms for most of the subunits.

Scaled-down purification protocol to access proteomic analysis of 20S proteasome from human tissue samples: comparison of normal and tumor colorectal cells.

The proteasome is a proteolytic complex that constitutes the main pathway for degradation of intracellular proteins in eukaryotic cells. It regulates many physiological processes and its dysfunction can lead to several pathologies like cancer. To study the 20S proteasome structure/activity relationship in cells that derive from human biopsy samples, we optimized an immuno-purification protocol for the analysis of samples containing a small number of cells using magnetic beads.

Purification and proteomic analysis of 20S proteasomes from human cells.

The 20S proteasome is a multicatalytic protein complex present in all eukaryotic cells. Associated to regulatory complexes, it plays a major role in cellular protein degradation and in the generation of Major Histocompatibility Complex (MHC) class I antigenic peptides. In mammalian cells, this symmetrical cylindrical complex is composed of two copies of 14 distinct subunits, three of which possess a proteolytic activity.

Effect of long-term exposure of SH-SY5Y cells to morphine: a whole cell proteomic analysis.

Background: Opiate addiction reflects plastic changes that endurably alter synaptic transmission within relevant neuronal circuits. The biochemical mechanisms of these adaptations remain largely unknown and proteomics-based approaches could lead to a broad characterization of the molecular events underlying adaptations to chronic drug exposure.

Results: Thus, we have started proteomic analyses of the effects of chronic morphine exposure in a recombinant human neuroblastoma SH-SY5Y clone that stably overexpresses the mu-opioid receptor.

Further insight into S-adenosylmethionine-dependent methyltransferases: structural characterization of Hma, an enzyme essential for the biosynthesis of oxygenated mycolic acids in Mycobacterium tuberculosis.

Mycolic acids are major and specific components of the cell envelope of Mycobacteria that include Mycobacterium tuberculosis, the causative agent of tuberculosis. Their metabolism is the target of the most efficient antitubercular drug currently used in therapy, and the enzymes that are involved in the production of mycolic acids represent important targets for the development of new drugs effective against multidrug-resistant strains. Among these are the S-adenosylmethionine-dependent methyltransferases (SAM-MTs) that catalyze the introduction of key chemical modifications in defined positions of mycolic acids.

An enzymatic cascade of Rab5 effectors regulates phosphoinositide turnover in the endocytic pathway.

Generation and turnover of phosphoinositides (PIs) must be coordinated in a spatial- and temporal-restricted manner. The small GTPase Rab5 interacts with two PI 3-kinases, Vps34 and PI3Kbeta, suggesting that it regulates the production of 3-PIs at various stages of the early endocytic pathway. Here, we discovered that Rab5 also interacts directly with PI 5- and PI 4-phosphatases and stimulates their activity.

Long-term morphine treatment enhances proteasome-dependent degradation of G beta in human neuroblastoma SH-SY5Y cells: correlation with onset of adenylate cyclase sensitization.

The initial aim of this study was to identify protein changes associated with long-term morphine treatment in a recombinant human neuroblastoma SH-SY5Y clone (sc2) stably overexpressing the human mu-opioid (MOP) receptor. In MOP receptor-overexpressing sc2 cells, short-term morphine exposure was found to be much more potent and efficacious in inhibiting forskolin-elicited production of cAMP, and long-term morphine exposure was shown to induce a substantially higher degree of opiate dependence, as reflected by adenylate cyclase sensitization, than it did in wild-type neuroblastoma cells. Differential proteomic analysis of detergent-resistant membrane rafts isolated from untreated and chronically morphine-treated sc2 cells revealed long-term morphine exposure to have reliably induced a 30 to 40% decrease in the abundance of five proteins, subsequently identified by mass spectrometry as G protein subunits alphai(2), alphai(3), beta(1), and beta(2), and prohibitin.

A quantitative proteomic approach using two-dimensional gel electrophoresis and isotope-coded affinity tag labeling for studying human 20S proteasome heterogeneity.

Mammalian proteasomes are macromolecular complexes formed of a catalytic 20S core associated to two regulatory complexes. The 20S core complex consists of four stacked rings of seven alpha or beta subunits. Three beta subunits contain a catalytic site and can be replaced by three interferon gamma-inducible counterparts to form the immunoproteasome.

The Rab5 effector Rabankyrin-5 regulates and coordinates different endocytic mechanisms.

The small GTPase Rab5 is a key regulator of clathrin-mediated endocytosis. On early endosomes, within a spatially restricted domain enriched in phosphatydilinositol-3-phosphate [PI(3)P], Rab5 coordinates a complex network of effectors that functionally cooperate in membrane tethering, fusion, and organelle motility. Here we discovered a novel PI(3)P-binding Rab5 effector, Rabankyrin-5, which localises to early endosomes and stimulates their fusion activity.

APPL proteins link Rab5 to nuclear signal transduction via an endosomal compartment.

Signals generated in response to extracellular stimuli at the plasma membrane are transmitted through cytoplasmic transduction cascades to the nucleus. We report the identification of a pathway directly linking the small GTPase Rab5, a key regulator of endocytosis, to signal transduction and mitogenesis. This pathway operates via APPL1 and APPL2, two Rab5 effectors, which reside on a subpopulation of endosomes.

Association of phospholamban with a cGMP kinase signaling complex.

The cGMP kinase signaling complex identified previously in tracheal smooth muscle membranes contains a number of cGMP kinase substrates termed G0 through G4. G0, G1, and G2 were identified as IP(3) receptor I (IP(3)RI), IRAG, and cGMP kinase I. Sequencing of purified G3 and G4 showed that these proteins were proteolytic cleavage products of IRAG.