技术资料

Synaptic plasticity is mediated by the dynamic localization of proteins to and from synapses. This is controlled,in part,through activity-induced palmitoylation of synaptic proteins. Here we report that the ability of the palmitoyl-acyl transferase,DHHC5,to palmitoylate substrates in an activity-dependent manner is dependent on changes in its subcellular localization. Under basal conditions,DHHC5 is bound to PSD-95 and Fyn kinase,and is stabilized at the synaptic membrane through Fyn-mediated phosphorylation of a tyrosine residue within the endocytic motif of DHHC5. In contrast,DHHC5's substrate,δ-catenin,is highly localized to dendritic shafts,resulting in the segregation of the enzyme/substrate pair. Neuronal activity disrupts DHHC5/PSD-95/Fyn kinase complexes,enhancing DHHC5 endocytosis,its translocation to dendritic shafts and its association with δ-catenin. Following DHHC5-mediated palmitoylation of δ-catenin,DHHC5 and δ-catenin are trafficked together back into spines where δ-catenin increases cadherin stabilization and recruitment of AMPA receptors to the synaptic membrane. View Publication

Pluripotent human embryonic stem cells (hESCs) have the capability of differentiating into different lineages based on specific environmental cues. We had previously shown that hESCs can be primed to differentiate into either neurons or glial cells,depending on the arrangement,geometry and size of their substrate topography. In particular,anisotropically patterned substrates like gratings were found to favour the differentiation of hESCs into neurons rather than glial cells. In this study,our aim is to elucidate the underlying mechanisms of topography-induced differentiation of hESCs towards neuronal lineages. We show that high actomyosin contractility induced by a nano-grating topography is crucial for neuronal maturation. Treatment of cells with the myosin II inhibitor (blebbistatin) and myosin light chain kinase inhibitor (ML-7) greatly reduces the expression level of microtubule-associated protein 2 (MAP2). On the other hand,our qPCR array results showed that PAX5,BRN3A and NEUROD1 were highly expressed in hESCs grown on nano-grating substrates as compared to unpatterned substrates,suggesting the possible involvement of these genes in topography-mediated neuronal differentiation of hESCs. Interestingly,YAP was localized to the cytoplasm of differentiating hESCs. Taken together,our study has provided new insights in understanding the mechanotransduction of topographical cues during neuronal differentiation of hESCs. View Publication

Alcohol abuse predisposes the host to bacterial infections. In response to bacterial infection,the bone marrow hematopoietic activity shifts toward granulocyte production,which is critical for enhancing host defense. This study investigated the hematopoietic precursor cell response to bacteremia and how alcohol affects this response. Acute alcohol intoxication was induced in BALB/c mice 30 min before initiation of Escherichia coli bacteremia. Bacteremia caused a significant increase in the number of bone marrow lineage (lin(-))-c-kit(+)Sca-1(+) cells. Marrow lin(-)c-kit(+)Sca-1(+) cells isolated from bacteremic mice showed an increase in CFU-granulocyte/macrophage activity compared with controls. In addition to enhanced proliferation of lin(-)c-kit(+)Sca-1(+) cells as reflected by BrdU incorporation,phenotypic inversion of lin(-)c-kit(+)Sca-1(+)Sca-1(-) cells primarily accounted for the rapid increase in marrow lin(-)c-kit(+)Sca-1(+) cells following bacteremia. Bacteremia increased plasma concentration of TNF-alpha. Culture of marrow lin(-)c-kit(+)Sca-1(+)Sca-1(-) cells with murine rTNF-alpha for 24 h caused a dose-dependent increase in conversion of these cells to lin(-)c-kit(+)Sca-1(+) cells. Sca-1 mRNA expression by the cultured cells was also up-regulated following TNF-alpha stimulation. Acute alcohol intoxication inhibited the increase in the number of lin(-)c-kit(+)Sca-1(+) cells in the bone marrow after E. coli infection. Alcohol impeded the increase in BrdU incorporation into marrow lin(-)c-kit(+)Sca-1(+) cells in response to bacteremia. Alcohol also suppressed the plasma TNF-alpha response to bacteremia and inhibited TNF-alpha-induced phenotypic inversion of lin(-)c-kit(+)Sca-1(+)Sca-1(-) cells in vitro. These data show that alcohol inhibits the hematopoietic precursor cell response to bacteremia,which may serve as one mechanism underlying the impaired host defense in alcohol abusers with severe bacterial infections. View Publication

Bone marrow (BM) hematopoietic cells are selectively sensitive to polycyclic aromatic hydrocarbons (PAH) in vivo. 7,12-Dimethylbenz(a)anthracene (DMBA),but not benzo(a)pyrene (BP),depletes BM hematopoietic cells in C57BL/6 mice. This difference is due to a BP-selective aryl hydrocarbon receptor (AhR)-mediated recovery. Colony-forming unit assays show suppression of lymphoid progenitors by each PAH within 6 h but a subsequent recovery,exclusively after BP treatment. Suppression of myeloid progenitors (6 h) occurs only for DMBA. Each progenitor responded equally to DMBA and BP in congenic mice expressing the PAH-resistant AhR (AhR(d)). AhR,therefore,mediates this BP recovery in each progenitor type. These PAH suppressions depend on Cyp1b1-mediated metabolism. Paradoxically,few genes responded to DMBA,whereas 12 times more responded to BP. Progenitor suppression by DMBA,therefore,occurs with minimal effects on the general BM population. Standard AhR-mediated stimulations (Cyp1a1,Cyp1b1,Ahrr) were similar for each PAH and for the specific agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin but were absent in AhR(d) mice. A group of 12 such AhR responses was sustained from 6 to 24 h. A second,larger set of BP responses (chemokines,cytokines,cyclooxygenase 2) differed in two respects; DMBA responses were low and BP responses declined extensively from 6 to 24 h. A third cluster exhibited BP-induced increases in protective genes (Nqo1,GST-mu) that appeared only after 12 h. Conversion of BP to quinones contributes oxidative signaling not seen with DMBA. We propose that genes in this second cluster,which share oxidative signaling and AhR activation,provide the AhR-dependent protection of hematopoietic progenitors seen for BP. View Publication

PURPOSE We investigated the effect of the racemic $\beta$-hydroxybutyrate precursor,R,S-1,3-butanediol (BD),on T-cell-related cytokine gene expression within stimulated peripheral blood mononuclear cells (PBMC) following prolonged,strenuous exercise. METHODS A repeated-measures,randomised,crossover study was conducted in nine healthy,trained male cyclists (age,26.7 ± 5.2 years; VO2peak,63.9 ± 2.5 mL kg-1 min-1). Participants ingested 0.35 g kg-1 of BD or placebo 30 min before and 60 min during 85 min of steady-state (SS) exercise,which preceded a {\~{}} 30 min time-trial (TT) (7 kJ kg-1). Blood samples were collected at pre-supplement,pre-exercise,post-SS,post-TT and 1-h post-TT. Whole blood cultures were stimulated with Staphylococcal enterotoxin B (SEB) for 24 h to determine T-cell-related interleukin (IL)-4,IL-10 and interferon (IFN)-$\gamma$ mRNA expression within isolated PBMCs in vitro. RESULTS Serum cortisol,total circulating leukocyte and lymphocyte,and T-cell subset concentrations were similar between trials during exercise and recovery (all p {\textgreater} 0.05). BD ingestion increased T-cell-related IFN-$\gamma$ mRNA expression compared with placebo throughout exercise and recovery (p = 0.011); however,IL-4 and IL-10 mRNA expression and the IFN-$\gamma$/IL-4 mRNA expression ratio were unaltered (all p {\textgreater} 0.05). CONCLUSION Acute hyperketonaemia appears to transiently amplify the initiation of the pro-inflammatory T-cell-related IFN-$\gamma$ response to an immune challenge in vitro during and following prolonged,strenuous exercise; suggesting enhanced type-1 T-cell immunity at the gene level. View Publication

Suprachiasmatic nucleus circadian oscillatory protein (SCOP) (a.k.a. PHLPP1) regulates long-term memory consolidation in the brain. Using a mouse model of controlled cortical impact (CCI) we tested if (1) brain tissue levels of SCOP/PHLPP1 increase after a traumatic brain injury (TBI),and (2) if SCOP/PHLPP1 gene knockout (KO) mice have improved (or worse) neurologic outcomes. Blood chemistry (pH,pCO2,pO2,pSO2,base excess,sodium bicarbonate,and osmolarity) and arterial pressure (MAP) differed in isoflurane anesthetized WT vs. KOs at baseline and up to 1 h post-injury. CCI injury increased cortical/hippocampal SCOP/PHLPP1 levels in WTs 7d and 14d post-injury. Injured KOs had higher brain tissue levels of phosphorylated AKT (pAKT) in cortex (14d post-injury),and higher levels of phosphorylated MEK (pMEK) in hippocampus (7d and 14d post-injury) and in cortex (7d post-injury). Consistent with an important role of SCOP/PHLPP1 on memory function,injured-KOs had near normal performance on the probe trial of the Morris water maze,whereas injured-WTs were impaired. CA1/CA3 hippocampal survival was lower in KOs vs. WTs 24 h post-injury but equivalent by 7d. No difference in 21d cortical lesion volume was detected. SCOP/PHLPP1 overexpression in cultured rat cortical neurons had no effect on 24 h cell death after a mechanical stretch-injury. View Publication

Adaptive transcriptional responses to oxygen deprivation (hypoxia) are mediated by the hypoxia-inducible factors (HIFs),heterodimeric transcription factors composed of two basic helix-loop-helix-PAS family proteins. The transcriptional activity of HIF is determined by the hypoxic stabilization of the HIF-alpha proteins. HIF-1alpha and HIF-2alpha exhibit high sequence homology but have different mRNA expression patterns; HIF-1alpha is expressed ubiquitously whereas HIF-2alpha expression is more restricted to certain tissues,e.g.,the endothelium,lung,brain,and neural crest derivatives. Germ-line deletion of either HIF subunit is embryonic lethal with unique features suggesting important roles for both HIF-alpha isoforms. Global deletion of Hif-2alpha results in distinct phenotypes depending on the mouse strain used for the mutation,clearly demonstrating an important role for HIF-2alpha in mouse development. The function of HIF-2alpha in adult life,however,remains incompletely understood. In this study,we describe the generation of a conditional murine Hif-2alpha allele and the effect of its acute postnatal ablation. Under very stringent conditions,we ablate Hif-2alpha after birth and compare the effect of acute global deletion of Hif-2alpha and Hif-1alpha. Our results demonstrate that HIF-2alpha plays a critical role in adult erythropoiesis,with acute deletion leading to anemia. Furthermore,although HIF-1alpha was first purified and cloned based on its affinity for the human erythropoietin (EPO) 3' enhancer hypoxia response element (HRE) and regulates Epo expression during mouse embryogenesis,HIF-2alpha is the critical alpha isoform regulating Epo under physiologic and stress conditions in adults. View Publication

Adenosine deaminase (ADA) deficiency is a disorder of the purine metabolism leading to combined immunodeficiency and systemic alterations,including skeletal abnormalities. We report that ADA deficiency in mice causes a specific bone phenotype characterized by alterations of structural properties and impaired mechanical competence. These alterations are the combined result of an imbalanced receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin axis,causing decreased osteoclastogenesis and an intrinsic defect of osteoblast function with subsequent low bone formation. In vitro,osteoblasts lacking ADA displayed an altered transcriptional profile and growth reduction. Furthermore,the bone marrow microenvironment of ADA-deficient mice showed a reduced capacity to support in vitro and in vivo hematopoiesis. Treatment of ADA-deficient neonatal mice with enzyme replacement therapy,bone marrow transplantation,or gene therapy resulted in full recovery of the altered bone parameters. Remarkably,untreated ADA-severe combined immunodeficiency patients showed a similar imbalance in RANKL/osteoprotegerin levels alongside severe growth retardation. Gene therapy with ADA-transduced hematopoietic stem cells increased serum RANKL levels and children's growth. Our results indicate that the ADA metabolism represents a crucial modulatory factor of bone cell activities and remodeling. View Publication

Metabolic labeling with stable isotopes is a prominent technique for comparative quantitative proteomics,and stable isotope labeling with amino acids in cell culture (SILAC) is the most commonly used approach. SILAC is,however,traditionally limited to simple tissue culture regimens and only rarely employed in the context of complex culturing conditions as those required for human embryonic stem cells (hESCs). Classic hESC culture is based on the use of mouse embryonic fibroblasts (MEFs) as a feeder layer,and as a result,possible xenogeneic contamination,contribution of unlabeled amino acids by the feeders,interlaboratory variability of MEF preparation,and the overall complexity of the culture system are all of concern in conjunction with SILAC. We demonstrate a feeder-free SILAC culture system based on a customized version of a commonly used,chemically defined hESC medium developed by Ludwig et al. and commercially available as mTeSR1 [mTeSR1 is a trade mark of WiCell (Madison,WI) licensed to STEMCELL Technologies (Vancouver,Canada)]. This medium,together with adjustments to the culturing protocol,facilitates reproducible labeling that is easily scalable to the protein amounts required by proteomic work flows. It greatly enhances the usability of quantitative proteomics as a tool for the study of mechanisms underlying hESCs differentiation and self-renewal. Associated data have been deposited to the ProteomeXchange with the identifier PXD000151. View Publication

Human embryonic stem cells (hESC) are difficult to adapt to 96-well plate assays,such as the MTT assay,because they survive best when plated as colonies,which are not easily counted and plated accurately. Two methods were developed to address this problem. In the first,ROCK inhibitor (ROCKi) was used,which allows accurate counting and plating of single hESC. In the second,small colonies were plated without ROCKi but with adaptations for accurate counting and plating. The MTT assay was also adapted for use with mouse neural stem cells. These methods allow the MTT assay to be conducted rapidly and accurately with high reproducibility between replicate experiments. When screening volatile chemicals in a 96-well plate,vapor effects may occur and dose ranges must be carefully defined. The methods were validated using the NIH assay guidance tool. These methodss could readily be translated to other 96-well plate assay. View Publication

Overcoming imatinib mesylate (IM) resistance and disease persistence in patients with chronic myeloid leukemia (CML) is of considerable importance to the issue of potential cure. Here we asked whether autocrine signaling contributes to survival of BCR/ABL+ cells in the presence of IM and nilotinib (NI; AMN107),a novel,more selective Abl inhibitor. Conditioned media (CM) of IM-resistant LAMA84 cell clones (R-CM) was found to substantially protect IM-naive LAMA cells and primary CML progenitors from IM- or NI-induced cell death. This was due to an increased secretion of the granulocyte-macrophage colony-stimulating factor (GM-CSF),which was identified as the causative factor mediating IM resistance in R-CM. GM-CSF elicited IM and NI drug resistance via a BCR/ABL-independent activation of the janus kinases 2 (JAK-2)/signal transducer and activator of transcription 5 (STAT-5) signaling pathway in GM-CSF receptor alpha receptor (CD116)-expressing cells,including primary CD34+/CD116+ GM progenitors (GMPs). Elevated mRNA and protein levels of GM-CSF were detected in IM-resistant patient samples,suggesting a contribution of GM-CSF secretion for IM and NI resistance in vivo. Importantly,inhibition of JAK-2 with AG490 abrogated GM-CSF-mediated STAT-5 phosphorylation and NI resistance in vitro. Together,adaptive autocrine secretion of GM-CSF mediates BCR/ABL-independent IM and NI resistance via activation of the antiapoptotic JAK-2/STAT-5 pathway. Inhibition of JAK-2 overcomes GM-CSF-induced IM and NI progenitor cell resistance,providing a rationale for the application of JAK-2 inhibitors to eradicate residual disease in CML. View Publication

OBJECTIVE True identity and specific set of markers to enrich endometrial stem cells still remains elusive. Present study was undertaken to further substantiate that very small embryonic-like stem cells (VSELs) are the true and elusive stem cells in adult mice endometrium. METHODS This was achieved by undertaking three sets of experiments. Firstly,SSEA-1+ and Oct-4??+??positive VSELs,sorted from GFP mice,were transplanted into the uterine horns of wild-type Swiss mice and GFP uptake was studied within the same estrus cycle. Secondly,uterine lumen was scratched surgically and OCT-4 expressing stem/progenitor cells were studied at the site of injury after 24-72 h. Thirdly,OCT-4????expression was studied in the endometrium and myometrium of adult mice after neonatal exposure to estradiol (20 µg/pup/day on days 5-7 after birth). RESULTS GFP??+??ve VSELs expressing SSEA-1 and Oct-4 engrafted and differentiated into the epithelial cells lining the lumen as well as the glands during the estrus stage when maximum remodeling occurs. Mechanical scratching activated tissue-resident,nuclear OCT-4 positive VSELs and slightly bigger 'progenitors' endometrial stem cells (EnSCs,cytoplasmic OCT-4) which underwent clonal expansion and further differentiated into luminal and glandular epithelial cells. Neonatal exposure to endocrine disruption resulted in increased numbers of OCT-4 positive VSELs/EnSCs in adult endometrium. DISCUSSION Results support the presence of functionally active VSELs in adult endometrium. VSELs self-renew and give rise to EnSCs that further differentiate into epithelial cells under normal physiological conditions. Also,VSELs are vulnerable to endocrine insults. To conclude VSELs are true and elusive uterine stem cells that maintain life-long uterine homeostasis and their dysregulation may result in various pathologies. View Publication