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Stress kinases in the modulation of metabolism and energy balance

J Mol Endocrinol. 2015 Oct;55(2):R11-22. doi: 10.1530/JME-15-0146.

Manieri E., Sabio G.

Obesity is a new global pandemic, with growing incidence and prevalence. This disease is associated with increased risk of several pathologies, including diabetes, cardiovascular diseases, and cancer. The mechanisms underlying obesity-associated metabolic changes are the focus of efforts to identify new therapies. Stress-activated protein kinases (SAPK), including cJun N-terminal kinases (JNKs) and p38, are required for cellular responses to metabolic stress and therefore might contribute to the pathogenesis of obesity. Tissue-specific knockout models support a cell-type-specific role for JNK isoforms, in particular JNK1, highlighting its importance in cell homeostasis and organ crosstalk. However, more efforts are needed to elucidate the specific roles of other JNK isoforms and p38 family members in metabolism and obesity. This review provides an overview of the role of SAPKs in the regulation of metabolism.

Structure and Sialyllactose Binding of the Carboxy-Terminal Head Domain of the Fibre from a Siadenovirus, Turkey Adenovirus 3

PLoS One. 2015 Sep 29;10(9):e0139339. doi: 10.1371/journal.pone.0139339.

Singh A.K., Berbís M.Á., Ballmann M.Z., Kilcoyne M., Menéndez M., Nguyen T.H., Joshi L., Cañada F.J., Jiménez-Barbero J., Benkő M., Harrach B., van Raaij MJ

Structure and Sialyllactose Binding of the Carboxy-Terminal Head Domain of the Fibre from a Siadenovirus, Turkey Adenovirus 3The virulent form of turkey adenovirus 3 (TAdV-3), also known as turkey hemorrhagic enteritis virus (THEV), is an economically important poultry pathogen, while the avirulent form is used as a vaccine. TAdV-3 belongs to the genus Siadenovirus. The carboxy-terminal region of its fibre does not have significant sequence similarity to any other adenovirus fibre heads of known structure. Two amino acid sequence differences between virulent and avirulent TAdV-3 map on the fibre head: where virulent TAdV-3 contains Ile354 and Thr376, avirulent TAdV-3 contains Met354 and Met376. We determined the crystal structures of the trimeric virulent and avirulent TAdV-3 fibre head domains at 2.2 Å resolution. Each monomer contains a beta-sandwich, which, surprisingly, resembles reovirus fibre head more than other adenovirus fibres, although the ABCJ-GHID topology is conserved in all. A beta-hairpin insertion in the C-strand of each trimer subunit embraces its neighbouring monomer. The avirulent and virulent TAdV-3 fibre heads are identical apart from the exact orientation of the beta-hairpin insertion. In vitro, sialyllactose was identified as a ligand by glycan microarray analysis, nuclear magnetic resonance spectroscopy, and crystallography. Its dissociation constant was measured to be in the mM range by isothermal titration calorimetry. The ligand binds to the side of the fibre head, involving amino acids Glu392, Thr419, Val420, Lys421, Asn422, and Gly423 binding to the sialic acid group. It binds slightly more strongly to the avirulent form. We propose that, in vivo, the TAdV-3 fibre may bind a sialic acid-containing cell surface component.

The peptidome of the Behçet's disease-associated HLA-B*51:01 includes two sub-peptidomes differentially shaped by ERAP1

Arthritis Rheumatol. 2015 Sep 11. doi: 10.1002/art.39430

Guasp P., Alvarez-Navarro C., Gomez-Molina P., Martín-Esteban A., Marcilla M., Barnea E., Admon A., de Castro J.A.

OBJECTIVE:To characterize the peptidome of the Behçet's disease-associated B*51:01 allotype, the differential features of major peptide subsets and their distinct ERAP1-mediated processing. METHODS: The endogenous B*51:01-bound peptidome was characterized from 721.221 transfectant cells, after affinity chromatography and acid extraction, by tandem mass spectrometry. Recombinant ERAP1 variants were used to digest synthetic B*51:01 ligands. HLA and TAP binding affinities of peptide ligands were calculated with well-established algorithms. ERAP1 and ERAP2 from 721.221 cells were characterized by genomic sequencing and Western blotting. RESULTS: The B*51:01 peptidome consisted of 29.5% octamers, 61.7% nonamers, 4.8% decamers and 4.0% longer peptides. The major peptide motif consisted of Pro and Ala at position (P)2, aliphatic/aromatic P3 residues, and Val and Ile at the C-terminal position. The ligands with Pro2 or Ala2 constituted two distinct sub-peptidomes. Peptides with Pro2 showed higher affinity for B*51:01 and lower affinity for TAP than those with Ala2. Most importantly, both peptide subsets drastically differed in the susceptibility of their P1 residues to ERAP1, revealing a distinct influence of this enzyme on both sub-peptidomes, which may alter their balance, affecting the global affinity of B*51:01/peptide complexes. CONCLUSION: ERAP1 has a significant influence on the B*51:01 peptidome and its affinity. This influence is based on drastically distinct effects on the Pro2 and Ala2 sub-peptidomes, whereby only the latter peptides are extensively destroyed, except when their P1 residues are ERAP1-resistant. This pattern provides a mechanism for the epistatic association of ERAP1 and B*51:01 in Behçet's disease. This article is protected by copyright.

The keepers of the ring: regulators of FtsZ assembly

FEMS Microbiol Rev. 2015 Sep 15. pii: fuv040

Ortiz C., Natale P., Cueto L., and Vicente M.

The keepers of the ring: regulators of FtsZ assemblyFtsZ, a GTPase distributed in the cytoplasm of most bacteria, is the major component of the machinery responsible for division (the divisome) in Escherichia coli. It interacts with additional proteins that contribute to its function forming a ring at the midcell that is essential to constrict the membrane. FtsZ is indirectly anchored to the membrane and it is prevented from polymerizing at locations where septation is undesired. Several properties of FtsZ are mediated by other proteins that function as keepers of the ring. ZipA and FtsA serve to anchor the ring, and together with a set of Zap proteins, they stabilize it. The MinCDE and SlmA proteins prevent the polymerization of FtsZ at sites other than the midcell. Finally, ClpP degrades FtsZ, an action prevented by ZipA. Many of the FtsZ keepers interact with FtsZ through a central hub located at its carboxy terminal end.

Pseudomonas putida KT2440 Metabolizes Glucose Through a Cycle Formed by Enzymes of the Entner-Doudoroff, Embden-Meyerhof-Parnas, and Pentose Phosphate Pathways

J Biol Chem. 2015 Sep 8. pii: jbc.M115.687749

Nikel P.I., Chavarria M., Fuhrer T., Sauer U., and de Lorenzo V.

The soil bacterium Pseudomonas putida KT2440 lacks a functional Embden-Meyerhof-Parnas (EMP) pathway, and glycolysis is known to proceed almost exclusively through the Entner-Doudoroff (ED) route. To investigate the raison d'etre of this metabolic arrangement, the distribution of periplasmic and cytoplasmic carbon fluxes were studied in glucose cultures of this bacterium by using 13C-labelled substrates, combined with quantitative physiology experiments, metabolite quantification, and in vitro enzymatic assays under both saturating and non-saturating, quasi in vivo conditions. Metabolic flux analysis demonstrated that 90% of the consumed sugar was converted into gluconate, entering central carbon metabolism as 6-phosphogluconate and further channeled into the ED pathway. Remarkably, about 10% of the triose phosphates were found to be recycled back to form hexose phosphates. This set of reactions merges activities belonging to the ED, the EMP (operating in a gluconeogenic fashion), and the pentose phosphate pathways to form an unforeseen metabolic architecture (EDEMP cycle). Determination of the NADPH balance revealed that the default metabolic state of P. putida KT2440 is characterized by a slight catabolic overproduction of reducing power. Cells growing on glucose thus run a biochemical cycle which favours NADPH formation. Since NADPH is required not only for anabolic functions but also for counteracting different types of environmental stress, such a cyclic operation may contribute to the physiological heftiness of this bacterium in its natural habitats.