The tyrosine kinase Syk regulates TPL2 activation signals

Tpl2/Cot is a serine/threonine kinase that plays a key physiological role in the regulation of immune responses to pro-inflammatory stimuli, including tumor necrosis factor-alpha (TNF-alpha). TNF-alpha stimulates the JNK, ERK, and p38 mitogen-activated protein kinases and the NF-kappaB pathway by recruiting RIP1 and TRAF2 to the TNF receptor 1. Here we showed that Tpl2 activation by TNF-alpha signals depends on the integrity of the Tpl2-interacting proteins RIP1 and TRAF2, which are required for the engagement of the ERK mitogen-activated protein kinase pathway. However, neither RIP1 nor TRAF2 overexpression was sufficient to activate Tpl2 and ERK. We also showed that Tpl2 activation by TNF-alpha depends on a tyrosine kinase activity that is detected in TNF-alpha-stimulated cells. Based on both genetic and biochemical evidence, we concluded that in a variety of cell types, Syk is the tyrosine kinase that plays an important role in the activation of Tpl2 upstream of ERK. These data therefore dissect the TNF receptor 1 proximal events that regulate Tpl2 and ERK and highlight a role for RIP1, TRAF2, and Syk in this pathway.     

TPL2 signalling: From Toll-like receptors-mediated ERK1/ERK2 activation to Cystic Fibrosis lung disease

Cystic Fibrosis (CF) is the most common lethal genetic recessive disorder, with a carrier frequency of 1 in 27 among North American Caucasians. Mitogen-activated protein kinases (MAPKs) and pro-inflammatory cytokines have crucial functions in the innate immune response of epithelial cells. They determine the inflammation status and the host response to pathogenic infections. However, in CF, bacterial-driven inflammation leads to tissue destruction, reduction in lung function and mortality. Recognition of invading pathogens is mediated in part by Toll-like receptors (TLR) activation of intracellular signalling cascade leading to cytokines’ synthesis. The protein kinase Tumour Progression Locus 2 (TPL2) is a key molecule in relaying inflammatory stimuli to ERK1/ERK2 MAPKs. In this review, we summarized the recent findings on TPL2 signalling and how TPL2 can contribute to the excessive inflammation found in CF. Pharmacologically targeting this kinase could have a significant benefit for CF patients dealing with chronic bacterial infections such as Pseudomonas aeruginosa.This article is part of a Directed Issue entitled: Cystic Fibrosis: From o-mics to cell biology, physiology, and therapeutic advances.     

Tumor progression locus 2 (TPL2): A Cot-plicated progression from inflammation to chronic liver disease

The cytoplasmic protein tumor progression locus 2 (TPL2), also known as cancer Osaka thyroid (Cot), or MAP3K8, is thought to have a significant role in a variety of cancers and illnesses and it is a key component in the activation pathway for the expression of inflammatory mediators. Despite the tight connection between inflammation and TPL2, its function has not been extensively studied in chronic liver disease (CLD), a major cause of morbidity and mortality worldwide. Here, we analyze more in detail the significance of TPL2 in CLD to shed light on the pathological and molecular transduction pattern of TPL2 during the progression of CLD. This might result in important advancements and enable progress in the diagnosis and treatment of CLD.     

Local Field Spectroscopy of Metal Dimers by TPL Microscopy

We report on two-photon photoluminescence (TPL) spectroscopy on metal dimers made of two gold nanoparticles separated by subwavelength distances. A direct comparison with far-field scattering measurements shows that TPL provides additional data on the structure modes of major importance for their use in surface-enhanced Raman scattering, enhanced fluorescence, and sensing.     

灰毛豆内生真菌淡紫拟青霉菌(TPL04)代谢产物的研究

从灰毛豆叶片中分离出内生真菌-淡紫拟青霉菌Purureocillium lilacinum(TPL04),对其发酵产物采用硅胶柱色谱、Sephadex LH-20凝胶色谱、制备薄层色谱、中压柱色谱及制备液相色谱等方法进行分离纯化,共获得8个单体化合物。通过波谱学方法并结合相关文献数据比对,化合物结构鉴定为5-羟基己酸-4-内酯(1)、(R)-4-苄基-2-噁唑烷酮(2)、2′-脱氧胸苷(3)、对羟基苯甲酸甲酯(4)、光色素(5)、β-胡萝卜苷(6)、尿嘧啶核苷(7)、己六醇(8)。其中化合物1、2、4是首次从淡紫拟青霉菌中分离得到,抑菌实验表明化合物4对水稻纹枯菌(Pellicularia sasakii)、辣椒疫霉菌(Phytophthora capsici)、草莓灰霉菌(Botrytis cinerea)、油菜菌核菌(Sclerotinia sclerotiorum)四种植物病原菌生长有抑制作用。     

The Protein Kinase TPL2 Is Essential for ERK1/ERK2 Activation and Cytokine Gene Expression in Airway Epithelial Cells Exposed to Pathogen-Associated Molecular Patterns (PAMPs)

The epithelium forms a physical barrier important to the detection of pathogens. P. aeruginosa infections are frequently encountered in Cystic Fibrosis lungs, lead to ERK1/ERK2 activation and contribute to tissue destruction. We report here that in bronchial airway epithelial cells (BEAS-2B), diffusible material from P. aeruginosa and TLR2, TLR3 and TLR5 ligands activates ERK1/ERK2 via the protein kinase TPL2 and not the growth factor receptor EGFR. Activation of TPL2 by these agonists in airway epithelial cells requires the protein kinases TAK1 and IKKβ in accordance with the previously reported model of activation of TPL2 in macrophages. Inhibition of TPL2 activity with a pharmacological inhibitor (Compound 1) not only prevented ERK1/ERK2 activation but also decreased cytokine synthesis in response to pathogen-associated molecular patterns. These results suggest that inhibition of the protein kinase TPL2 is an attractive strategy to decrease inflammation in the lungs when it is not warranted.     

Solvent-impregnated resins as an in situ product recovery tool for phenol recovery from Pseudomonas putida S12TPL fermentations

The sustainable production of fine/bulk chemicals is often hampered by product toxicity and inhibition to the producing micro-organisms. Consequently, the product must be removed from the micro-organisms' environment. To achieve this, so-called solvent-impregnated resins (SIRs) as well as commercial resins have been added to a Pseudomonas putida S12TPL fermentation that produces phenol as a model compound from glucose. The SIRs contained an ionic liquid which extracts phenol effectively. It was observed that the addition of these particles resulted in an increased phenol production of more than a fourfold while the commercial resin (XAD-4) which is widely used in aromatic removal from aqueous phases, only gave a 2.5-fold increase in volumetric production.     

Crystal structures of the Tie2 receptor ectodomain and the angiopoietin-2-Tie2 complex

The Tie receptor tyrosine kinases and their angiopoietin (Ang) ligands play central roles in developmental and tumor-induced angiogenesis. Here we present the crystal structures of the Tie2 ligand-binding region alone and in complex with Ang2. In contrast to prediction, Tie2 contains not two but three immunoglobulin (Ig) domains, which fold together with the three epidermal growth factor domains into a compact, arrowhead-shaped structure. Ang2 binds at the tip of the arrowhead utilizing a lock-and-key mode of ligand recognition-unique for a receptor kinase-where two complementary surfaces interact with each other with no domain rearrangements and little conformational change in either molecule. Ang2-Tie2 recognition is similar to antibody-protein antigen recognition, including the location of the ligand-binding site within the Ig fold. Analysis of the structures and structure-based mutagenesis provide insight into the mechanism of receptor activation and support the hypothesis that all angiopoietins interact with Tie2 in a structurally similar manner.     

Stereospecific 2'-amination and 2'-chlorination of adenosine by Actinomadura in the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin

2'-Amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin (2'-CldCF) are two nucleoside antibiotics produced by Actinomadura. The biosynthesis of these two nucleoside antibiotics has been studied by the addition of [U-14C]adenosine with or without unlabeled adenine to cultures of Actinomadura. By this experimental approach, it is possible to demonstrate that adenosine is the direct precursor for the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-CldCF. These conclusions are based on the observation that the percentage distribution of 14C in the aglyconic and pentofuranosyl moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were similar to the distribution of 14C in the adenine and ribosyl moieties of the [U-14C]adenosine (i.e., 48:52) added to cultures of Actinomadura. Experimentally, the percentage distribution of 14C in the (i) adenine:2-amino-2-deoxy-beta-D-ribofuranose of 2'-amino-2'-deoxyadenosine is 51:49; (ii) 8-(R)-3,6,7,8-tetrahydroimidazo[4,5-d]-[1,3-diazepin-8-o1]:2 -chloro-2- beta-D-ribofuranose of 2'-CldCF is 45:55; and (iii) adenine:ribose of the adenosine isolated from the RNA of Actinomadura is 42:58. Further proof that adenosine is the direct precursor for the biosynthesis 2'-amino-2'-deoxyadenosine and 2'-CldCF was demonstrated by the addition of 75 mumol of unlabeled adenine together with [U-14C]adenosine to nucleoside-producing cultures of Actinomadura. The percentage distribution of 14C in the aglycon and the sugar moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were 46:54 and 47:53, respectively; the percentage distribution of 14C in the adenine and ribose moieties of the adenosine isolated from the RNA of Actinomadura was 51:49. These data show that the hydroxyl on C-2' of the ribosyl moiety of adenosine undergoes a replacement by a 2'-amino or a 2'-chloro group to form 2'-amino-2'-deoxyadenosine or 2'-CldCF with retention of stereconfiguration at C-2'. Finally, Actinomadura can utilize inorganic chloride from the medium as demonstrated by the isolation of [36Cl]2'-CldCF following the addition of [36Cl]chloride to the culture medium. Mechanisms for the regioselective modification of the C-2' hydroxyl group and stereospecific insertion of the amino and chloro groups are discussed.     

Tight interplay between the Ca2+ affinity of the cardiac SERCA2 Ca2+ pump and the SERCA2 expression level

A reduced activity of the sarcoplasmic reticulum Ca2+ pump SERCA2a is a hallmark of cardiac dysfunction in heart failure. In SERCA2b/b mice, the normal SERCA2a isoform is replaced by SERCA2b, displaying a higher Ca2+ affinity. This elicited decreased cardiac SERCA2 expression and cardiac hypertrophy. Here, the interplay was studied between the increased Ca2+ affinity and a reduced expression of the pump and its role in the cardiac remodeling was investigated. First, SERCA2b/b mice were crossed with SERCA2b transgenes to boost cardiac SERCA2b expression. However, the enforced expression of SERCA2b was spontaneously countered by an increased inhibition by phospholamban (PLB), reducing the pump's Ca2+ affinity. Moreover, the higher SERCA2 content did not prevent hypertrophy. Second, we studied heterozygous SERCA2b/WT mice, which also express lower SERCA2 levels compared to wild-type. Hypertrophy was not observed. In heterozygotes, SERCA2b expression was specifically suppressed, explaining the reduced SERCA2 content. The SERCA2b/WT model strikingly differs from the homozygote models because SERCA2a (not SERCA2b) is the major isoform and because the inhibition of the pump by PLB is decreased instead of being increased. Thus, a tight correlation exists between the SERCA2 levels and Ca2+ affinity (controlled by PLB). This compensatory response may be important to prevent cardiac remodeling.     

Neuroprotective roles of the P2Y2 receptor

Purinergic signaling plays a unique role in the brain by integrating neuronal and glial cellular circuits. The metabotropic P1 adenosine receptors and P2Y nucleotide receptors and ionotropic P2X receptors control numerous physiological functions of neuronal and glial cells and have been implicated in a wide variety of neuropathologies. Emerging research suggests that purinergic receptor interactions between cells of the central nervous system (CNS) have relevance in the prevention and attenuation of neurodegenerative diseases resulting from chronic inflammation. CNS responses to chronic inflammation are largely dependent on interactions between different cell types (i.e., neurons and glia) and activation of signaling molecules including P2X and P2Y receptors. Whereas numerous P2 receptors contribute to functions of the CNS, the P2Y(2) receptor is believed to play an important role in neuroprotection under inflammatory conditions. While acute inflammation is necessary for tissue repair due to injury, chronic inflammation contributes to neurodegeneration in Alzheimer's disease and occurs when glial cells undergo prolonged activation resulting in extended release of proinflammatory cytokines and nucleotides. This review describes cell-specific and tissue-integrated functions of P2 receptors in the CNS with an emphasis on P2Y(2) receptor signaling pathways in neurons, glia, and endothelium and their role in neuroprotection.