Two new species of Steccherinum (Polyporales, Basidiomycota) from southern China based on morphology and DNA sequence data.

Two new wood-inhabiting fungal species, Steccherinum hirsutum and S. yunnanense spp. nov., are proposed based on a combination of morphological features and molecular evidence. Sequences of internal transcribed spacer and large subunit region of nuculear ribosomal RNA gene of the studied samples were generated, and phylogenetic analyses were performed using maximum likelihood, maximum parsimony and bayesian inference methods. Steccherinum hirsutum is characterized by an annual growth habit, stipitate basidiocarps with scarlet to red, odontioid hymenial surface, a dimitic hyphal system with clamped generative hyphae negative in Melzer's reaction, and acyanophilous basidiospores measuring 2.5-3.5 × 1.5-2.5 µm. Steccherinum yunnanense is distinguished by resupinate basidiomata with odontioid hymenial surface, a dimitic hyphal system with clamped generative hyphae, strongly encrusted cystidia and ellipsoid, hyaline, thin-walled, smooth basidiospores (3.5-4.5 × 2-3.5 µm). The phylogenetic analyses comfirmed that two new species nest in Steccherinum, in the residual polyporoid clade.

A phylogenetic and taxonomic study on Steccherinum (Polyporales, Basidiomycota): Focusing on three new Steccherinum species from southern China.

The wood-inhabiting fungi play an integral role in wood degradation and the cycle of matter in the ecological system. They are considered as the "key player" in wood decomposition, because of their ability to produce all kinds of enzymes that break down woody lignin, cellulose and hemicellulose. In the present study, three new wood-inhabiting fungal species, Steccherinum fissurutum, S. punctatum and S. subtropicum spp. nov., collected from southern China, are proposed based on a combination of morphological features and molecular evidence. Steccherinum fissurutum is characterized by the resupinate, subceraceous basidiomata with cracked hymenophore, a monomitic hyphal system with clamped generative hyphae and cylindrical basidiospores; S. punctatum is characterized by the annual, punctate basidiomata with leathery hymenophore, cylindrical, strongly encrusted cystidia and ellipsoid basidiospores (3.6-4.5 ×2.6-3.4 µm); S. subtropicum is characterized by its effuse-reflexed basidiomata, a odontioid hymenophore with pink to lilac hymenial surface and ellipsoid basidiospores measuring as (2.8-3.4 × 2.0-2.7 µm). Sequences of ITS and nLSU rRNA markers of the studied samples were generated, and phylogenetic analyses were performed with maximum likelihood, maximum parsimony, and Bayesian inference methods. The ITS+nLSU analysis of the family Steccherinaceae indicated that the three new species clustered into the genus Steccherinum. Based on further analysis of ITS+nLSU dataset, the phylogenetic analysis confirmed that S. subtropicum was sister to S. enuispinum; S. fissurutum formed a monophyletic lineage; S. punctatum grouped with a clade comprised S. straminellum and S. ciliolatum.

Duodenal-Jejunal Bypass Ameliorates Type 2 Diabetes Mellitus by Activating Insulin Signaling and Improving Glucose Utilization in the Brain.

BACKGROUND: Duodenal-jejunal bypass (DJB) can dramatically improve type 2 diabetes independent of weight loss and food restriction. Increasing evidence has demonstrated that brain insulin signaling plays an important role in the pathophysiology of type 2 diabetes. This study explores whether the antidiabetic effect of DJB is involved in brain insulin signaling activation and brain glucose utilization. METHODS: A diabetic rat model was established by high-fat and high-glucose diet. DJB or sham surgery was performed in diabetic rats. 18F-FDG PET scanning was used to detect glucose uptake in different organs, particularly in the brain. The levels of glucose transporters, glucose utilization-related proteins (HK1 and PFK2), insulin, and insulin signaling pathway-related proteins (InsR, IRS1/2, PI3K, and p-Akt) in the brain tissues were evaluated and analyzed. RESULTS: The results showed that DJB significantly improved basal glycemic parameters and reversed the decreasing glucose uptake in the brains of type 2 diabetic rats. DJB significantly increased not only the expression levels of brain insulin, IRS1/2, PI3K, and p-Akt but also the levels of the glucose utilization enzymes HK1 and PFK2 in the brain. CONCLUSION: These results indicate that enhanced brain insulin signaling transduction and brain glucose utilization play important roles in the antidiabetic effect of DJB.

Adaptive Activation of a Stress Response Pathway Improves Learning and Memory Through Gs and ß-Arrestin-1-Regulated Lactate Metabolism.

BACKGROUND: Stress is a conserved physiological response in mammals. Whereas moderate stress strengthens memory to improve reactions to previously experienced difficult situations, too much stress is harmful. METHODS: We used specific ß-adrenergic agonists, as well as ß2-adrenergic receptor (ß2AR) and arrestin knockout models, to study the effects of adaptive ß2AR activation on cognitive function using Morris water maze and object recognition experiments. We used molecular and cell biological approaches to elucidate the signaling subnetworks. RESULTS: We observed that the duration of the adaptive ß2AR activation determines its consequences on learning and memory. Short-term formoterol treatment, for 3 to 5 days, improved cognitive function; however, prolonged ß2AR activation, for more than 6 days, produced harmful effects. We identified the activation of several signaling networks downstream of ß2AR, as well as an essential role for arrestin and lactate metabolism in promoting cognitive ability. Whereas Gs-protein kinase A-cyclic adenosine monophosphate response element binding protein signaling modulated monocarboxylate transporter 1 expression, ß-arrestin-1 controlled expression levels of monocarboxylate transporter 4 and lactate dehydrogenase A through the formation of a ß-arrestin-1/phospho-mitogen-activated protein kinase/hypoxia-inducible factor-1α ternary complex to upregulate lactate metabolism in astrocyte-derived U251 cells. Conversely, long-term treatment with formoterol led to the desensitization of ß2ARs, which was responsible for its decreased beneficial effects. CONCLUSIONS: Our results not only revealed that ß-arrestin-1 regulated lactate metabolism to contribute to ß2AR functions in improved memory formation, but also indicated that the appropriate management of one specific stress pathway, such as through the clinical drug formoterol, may exert beneficial effects on cognitive abilities.

Different downstream signalling of CCK1 receptors regulates distinct functions of CCK in pancreatic beta cells.

BACKGROUND AND PURPOSE: Cholecystokinin (CCK) is secreted by intestinal I cells and regulates important metabolic functions. In pancreatic islets, CCK controls beta cell functions primarily through CCK1 receptors, but the signalling pathways downstream of these receptors in pancreatic beta cells are not well defined. EXPERIMENTAL APPROACH: Apoptosis in pancreatic beta cell apoptosis was evaluated using Hoechst-33342 staining, TUNEL assays and Annexin-V-FITC/PI staining. Insulin secretion and second messenger production were monitored using ELISAs. Protein and phospho-protein levels were determined by Western blotting. A glucose tolerance test was carried out to examine the functions of CCK-8s in streptozotocin-induced diabetic mice. KEY RESULTS: The sulfated carboxy-terminal octapeptide CCK26-33 amide (CCK-8s) activated CCK1 receptors and induced accumulation of both IP3 and cAMP. Whereas Gq -PLC-IP3 signalling was required for the CCK-8s-induced insulin secretion under low-glucose conditions, Gs -PKA/Epac signalling contributed more strongly to the CCK-8s-mediated insulin secretion in high-glucose conditions. CCK-8s also promoted formation of the CCK1 receptor/ß-arrestin-1 complex in pancreatic beta cells. Using ß-arrestin-1 knockout mice, we demonstrated that ß-arrestin-1 is a key mediator of both CCK-8s-mediated insulin secretion and of its the protective effect against apoptosis in pancreatic beta cells. The anti-apoptotic effects of ß-arrestin-1 occurred through cytoplasmic late-phase ERK activation, which activates the 90-kDa ribosomal S6 kinase-phospho-Bcl-2-family protein pathway. CONCLUSIONS AND IMPLICATIONS: Knowledge of different CCK1 receptor-activated downstream signalling pathways in the regulation of distinct functions of pancreatic beta cells could be used to identify biased CCK1 receptor ligands for the development of new anti-diabetic drugs.

Constitutive Gαi coupling activity of very large G protein-coupled receptor 1 (VLGR1) and its regulation by PDZD7 protein.

The very large G protein-coupled receptor 1 (VLGR1) is a core component in inner ear hair cell development. Mutations in the vlgr1 gene cause Usher syndrome, the symptoms of which include congenital hearing loss and progressive retinitis pigmentosa. However, the mechanism of VLGR1-regulated intracellular signaling and its role in Usher syndrome remain elusive. Here, we show that VLGR1 is processed into two fragments after autocleavage at the G protein-coupled receptor proteolytic site. The cleaved VLGR1 ß-subunit constitutively inhibited adenylate cyclase (AC) activity through Gαi coupling. Co-expression of the Gαiq chimera with the VLGR1 ß-subunit changed its activity to the phospholipase C/nuclear factor of activated T cells signaling pathway, which demonstrates the Gαi protein coupling specificity of this subunit. An R6002A mutation in intracellular loop 2 of VLGR1 abolished Gαi coupling, but the pathogenic VLGR1 Y6236fsx1 mutant showed increased AC inhibition. Furthermore, overexpression of another Usher syndrome protein, PDZD7, decreased the AC inhibition of the VLGR1 ß-subunit but showed no effect on the VLGR1 Y6236fsx1 mutant. Taken together, we identified an independent Gαi signaling pathway of the VLGR1 ß-subunit and its regulatory mechanisms that may have a role in the development of Usher syndrome.

A stress response pathway in mice upregulates somatostatin level and transcription in pancreatic delta cells through Gs and ß-arrestin 1.

AIMS/HYPOTHESIS: Somatostatin secretion from islet delta cells plays an important role in regulating islet function and is tightly controlled by environmental changes. Activation of the adrenergic system promoted somatostatin secretion from islet delta cells; however, the role of the adrenergic system in regulating somatostatin content and transcription has not been defined. An imbalance between the somatostatin content and its secretion may cause dysfunctions in the islet delta cells. We have investigated the role of the adrenergic system in the modulation of somatostatin content and transcription in pancreatic delta cells and the detailed underlying mechanisms of this regulation. METHODS: The stress hormone adrenaline (epinephrine), specific adrenergic agonists or specific adrenergic antagonists were applied to islets from either wild-type or specific adrenergic receptor knockout mice and pancreatic delta cell lines to investigate their effects on somatostatin content and transcription. The GloSensor assay, quantitative real-time PCR, western blots and the dual luciferase assay were used to monitor the cAMP level, somatostatin expression, activations of kinases and transcriptional factors. Arrb1 knockout mice, specific Creb or Pax6 mutations and specific kinase inhibitors were used to dissect the signalling pathway. RESULTS: Adrenaline and isoprenaline increased somatostatin content and transcription through the activation of ß1-/ß2-adrenergic receptors (ß1-/ß2ARs). The somatostatin content in ß1AR(-/-) /ß2AR(-/-) (Adrb1/Adrb2 knockout) mice was 50% lower than in ß1AR(+/+)/ß2AR (+/+) mice. Two parallel signalling pathways, Gs-cAMP-protein kinase A (PKA)-cAMP response element binding protein (CREB) and ß-arrestin 1-extracellular signal-related kinase (ERK)-paired box protein 6 (PAX6), cooperatively regulated isoprenaline-induced somatostatin transcription. CONCLUSIONS/INTERPRETATION: A stress pathway increased somatostatin content and transcription through ß-adrenergic agonism. ß-Arrestin1, ERK and PAX6 are important pancreatic delta cell regulators in addition to cAMP, PKA and CREB. Dysfunction of ß-adrenergic agonism may impair pancreatic delta cell function.

Molecular mechanism of ERK dephosphorylation by striatal-enriched protein tyrosine phosphatase.

Striatal-enriched tyrosine phosphatase (STEP) is an important regulator of neuronal synaptic plasticity, and its abnormal level or activity contributes to cognitive disorders. One crucial downstream effector and direct substrate of STEP is extracellular signal-regulated protein kinase (ERK), which has important functions in spine stabilisation and action potential transmission. The inhibition of STEP activity toward phospho-ERK has the potential to treat neuronal diseases, but the detailed mechanism underlying the dephosphorylation of phospho-ERK by STEP is not known. Therefore, we examined STEP activity toward para-nitrophenyl phosphate, phospho-tyrosine-containing peptides, and the full-length phospho-ERK protein using STEP mutants with different structural features. STEP was found to be a highly efficient ERK tyrosine phosphatase that required both its N-terminal regulatory region and key residues in its active site. Specifically, both kinase interaction motif (KIM) and kinase-specific sequence of STEP were required for ERK interaction. In addition to the N-terminal kinase-specific sequence region, S245, hydrophobic residues L249/L251, and basic residues R242/R243 located in the KIM region were important in controlling STEP activity toward phospho-ERK. Further kinetic experiments revealed subtle structural differences between STEP and HePTP that affected the interactions of their KIMs with ERK. Moreover, STEP recognised specific positions of a phospho-ERK peptide sequence through its active site, and the contact of STEP F311 with phospho-ERK V205 and T207 were crucial interactions. Taken together, our results not only provide the information for interactions between ERK and STEP, but will also help in the development of specific strategies to target STEP-ERK recognition, which could serve as a potential therapy for neurological disorders. Regulation of phospho-ERK by STEP underlies important neuronal activities. A detailed enzymologic characterisation and cellular studies of STEP revealed that specific residues in KIM and active site mediated ERK recognition. Structural differences between the KIM-ERK interfaces and the active site among different ERK phosphatases could be targeted to develop specific STEP inhibitor, which has therapeutic potential for neurological disorders. PKA, protein kinase A & NGF, nerve growth factor.

ß2-adrenergic receptor and astrocyte glucose metabolism.

Astrocyte glucose metabolism functions to maintain brain activity in both normal and stress conditions. Dysregulation of astrocyte glucose metabolism relates to development of neuronal disease, such as multiple sclerosis and Alzheimer's disease. In response to acute stress, beta2-adrenergic receptor is activated and initiates multiple signaling events mediated by Gs, Gi, arrestin, or other effectors depending on specific cellular contexts. In astrocytes, beta2-adrenergic receptor promotes glucose uptake through GLUT1 and accelerates glycogen degradation via coupling to Gs and second messenger cAMP-dependent pathway. Beta2-adrenergic receptor may regulate other steps in astrocyte glucose metabolism, such as lactate production or transduction. Inappropriate regulation of beta2-adrenergic receptor activity can disrupt normal glucose metabolism, and leads to accelerate neuronal disease development. It was demonstrated that the absence of beta2-adrenergic receptor in astrocytes occurred in multiple sclerosis patients, and the increased beta2-adrenergic receptor activity relates to Alzheimer's disease. A clear view of beta2-adrenergic receptor-mediated signaling pathways in regulating astrocyte glucose metabolism could help us to develop neuronal diseases treatment by targeting to the beta2-adrenergic receptor.