Therapy of human tumors in NOD/SCID mice with patient-derived reactivated memory T cells from bone marrow

In an analysis of 84 primary-operated breast cancer patients and 11 healthy donors, we found that the bone marrow of most patients contained memory T cells with specificity for tumor-associated antigens. Patients' bone marrow and peripheral blood contained CD8+ T cells that specifically bound HLA/peptide tetramers. In short-term culture with autologous dendritic cells pre-pulsed with tumor lysates, patients' memory T cells from bone marrow (but not peripheral blood) could be specifically reactivated to interferon-gamma-producing and cytotoxic effector cells. A single transfer of restimulated bone-marrow T cells into NOD/SCID mice caused regression of autologous tumor xenotransplants associated with infiltration by human T cells and tumor-cell apoptosis and necrosis. T cells from peripheral blood showed much lower anti-tumor reactivity. Our findings reveal an innate, specific recognition of breast cancer antigens and point to a possible novel cancer therapy using patients' bone-marrow-derived memory T cells.

cAMP-dependent phosphorylation stimulates water permeability of aquaporin-collecting duct water channel protein expressed in Xenopus oocytes

Among water channel proteins (aquaporins), aquaporin-collecting duct (AQP-CD) is the vasopressin-regulated water channel. Vasopressin causes cAMP production in the renal collecting duct cells, and this is believed to lead to exocytic insertion of water channel into the apical membrane (shuttle hypothesis). AQP-CD contains a consensus sequence for cAMP-dependent protein kinase, residues at positions 253-256 (Arg-Arg-Gln-Ser). To determine the role of this site, Ser-256 was substituted for Ala, Leu, Thr, Asp, or Glu by site-directed mutagenesis. In Xenopus oocytes injected with wild-type or mutated AQP-CD cRNAs, osmotic water permeability (Pf) was 4.8-7.7 times higher than Pf of water-injected oocytes. Incubation with cAMP plus forskolin or direct cAMP injection into the oocytes increased Pf of wild-type, but not mutated, AQP-CD-expressing oocytes, whereas the amounts of AQP-CD expression were similar in wild and mutated types as identified by Western blot analysis. In vitro phosphorylation studies of AQP-CD proteins expressed in oocyte showed that cAMP-dependent protein kinase phosphorylated wild-type, but not mutated, AQP-CD proteins. Phosphoamino acid analysis revealed that this phosphorylation occurred at the serine residue. Moreover, phosphorylation of AQP-CD protein in intact rat kidney medulla tissues was stimulated by incubation with cAMP. Our data suggest that cAMP stimulates water permeability of AQP-CD by phosphorylation. This process may contribute to the vasopressin-regulated water permeability of collecting duct in addition to the apical insertion of AQP-CD by exocytosis.

Molecular and functional analysis of a novel neuronal vesicular glutamate transporter

Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. Packaging and storage of glutamate into glutamatergic neuronal vesicles requires ATP-dependent vesicular glutamate uptake systems, which utilize the electrochemical proton gradient as a driving force. VGLUT1, the first identified vesicular glutamate transporter, is only expressed in a subset of glutamatergic neurons. We report here the molecular cloning and functional characterization of a novel glutamate transporter, VGLUT2, from mouse brain. VGLUT2 has all major functional characteristics of a synaptic vesicle glutamate transporter, including ATP dependence, chloride stimulation, substrate specificity, and substrate affinity. It has 75 and 79% amino acid identity with human and rat VGLUT1, respectively. However, expression patterns of VGLUT2 in brain are different from that of VGLUT1. In addition, VGLUT2 activity is dependent on both membrane potential and pH gradient of the electrochemical proton gradient, whereas VGLUT1 is primarily dependent on only membrane potential. The presence of VGLUT2 in brain regions lacking VGLUT1 suggests that the two isoforms together play an important role in vesicular glutamate transport in glutamatergic neurons.

Src family kinase oncogenic potential and pathways in prostate cancer as revealed by AZD0530

Prostate cancer is the most frequently diagnosed cancer in American men. We have previously demonstrated that Src mediates androgen-independent proliferation in prostate cancer. We sought to investigate the Src-mediated oncogenic pathways and tumor biology using AZD0530, a novel Src family kinase/Abl dual-kinase inhibitor that is entering phase II clinical trials. We show that while both Src and Abl are expressed in all prostate cancer cell lines, Src but not Abl is activated in the prostate. Furthermore, Src activation is inhibited by AZD0530 in a rapid and dose-dependent manner. We show that Src mediates cell proliferation in DU145 and PC3 cells at the G1 phase of cell cycle. Src inhibition resulted in decreased binding of beta-catenin to the promoters of G1 phase cell cycle regulators cyclin D1 and c-Myc. C-Myc may also be regulated at the protein level by extracellular signal-regulated kinase 1/2 and GSK3beta. Cell motility factors focal adhesion kinase, p130CAS and paxillin activation in DU145 and PC3 cells were also inhibited. Administration of AZD0530 in mice reduced orthotopic DU145 xenograft growth by 45%. We have further delineated the Src-mediated oncogenic growth and migration pathways in prostate cancer and established mechanistic rationale for Src inhibition as novel therapy in the treatment of prostate cancer.

Proximal sequence element-binding transcription factor (PTF) is a multisubunit complex required for transcription of both RNA polymerase II- and RNA polymerase III-dependent small nuclear RNA genes

The proximal sequence element (PSE), found in both RNA polymerase II (Pol II)- and RNA Pol III-transcribed small nuclear RNA (snRNA) genes, is specifically bound by the PSE-binding transcription factor (PTF). We have purified PTF to near homogeneity from HeLa cell extracts by using a combination of conventional and affinity chromatographic methods. Purified PTF is composed of four polypeptides with apparent molecular masses of 180, 55, 45, and 44 kDa. A combination of preparative electrophoretic mobility shift and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses has conclusively identified these four polypeptides as subunits of human PTF, while UV cross-linking experiments demonstrate that the largest subunit of PTF is in close contact with the PSE. The purified PTF activates transcription from promoters of both Pol II- and Pol III-transcribed snRNA genes in a PSE-dependent manner. In addition, we have investigated factor requirements in transcription of Pol III-dependent snRNA genes. We show that in extracts that have been depleted of TATA-binding protein (TBP) and associated factors, recombinant TBP restores transcription from U6 and 7SK promoters but not from the VAI promoter, whereas the highly purified TBP-TBP-associated factor complex TFIIIB restores transcription from the VAI but not the U6 or 7SK promoter. Furthermore, by complementation of heat-treated extracts lacking TFIIIC activity, we show that TFIIIC1 is required for transcription of both the 7SK and VAI genes, whereas TFIIIC2 is required only for transcription of the VAI gene. From these observations, we conclude (i) that PTF and TFIIIC2 function as gene-specific as gene-specific factors for PSE-and B-box-containing Pol III genes, respectively, (ii) that the form of TBP used by class III genes with upstream promoter elements differs from the from used by class III genes with internal promoters, and (iii) that TFIIIC1 is required for both internal and external Pol III promoters.

Molecular cloning, functional characterization, tissue distribution, and chromosomal localization of a human, small intestinal sodium-phosphate (Na+-Pi) transporter (SLC34A2)

Phosphate plays a crucial role in cellular metabolism, and its homeostatic regulation in intestinal and renal epithelia is critical. Apically expressed sodium-phosphate (Na(+)-P(i)) transporters play a critical role in this regulation. We have isolated a cDNA (HGMW-approved symbol SLC34A2) encoding a novel human small intestinal Na(+)-P(i) transporter. The cDNA is shown to be 4135 bp in length with an open reading frame that predicts a 689-amino-acid polypeptide. The putative protein has 76% homology to mouse intestinal type II Na(+)-P(i) transporter (Na/Pi-IIb) and lower homologies with renal type II Na(+)-P(i) transporters. Northern blots showed a singular transcript of 5.0 kb in human lung, small intestine, and kidney. Computer analysis suggests a protein with 11 transmembrane domains and several potential posttranslational modification sites. Functional characterization in Xenopus laevis oocytes showed that this cDNA encodes a functional Na(+)-P(i) transporter. Furthermore, the gene encoding this cDNA was mapped to human chromosome 4p15.1-p15.3 by the FISH method.

Transcription factor ZBP-89 cooperates with histone acetyltransferase p300 during butyrate activation of p21waf1 transcription in human cells

Inducible p53-independent regulation of the cyclin-dependent kinase inhibitor p21(waf1) transcription is mediated through proximal GC-rich sites. Prior studies have shown that Sp1, Sp3, and the histone acetylase co-activator p300 are components of the complexes binding to these sites. Although Sp1 and Sp3 collaborate with p300, a direct interaction between Sp1 and p300 does not occur. This study sought to determine whether ZBP-89 rather than Sp1 is the direct target of p300 during butyrate induction of p21(waf1). ZBP-89 (BFCOL1, BERF-1, ZNF 148) is a Krüppel-type zinc finger transcription factor that binds to GC-rich elements and represses or activates known target genes. Adenoviral-mediated expression of ZBP-89 in HT-29 cells revealed that ZBP-89 potentiates butyrate induction of endogenous p21(waf1) gene expression. Further, cotransfection of a ZBP-89 expression vector with a 2.3-kilobase p21(waf1) reporter recapitulated the potentiation by butyrate. DNase I footprinting analysis of the human p21(waf1) promoter with recombinant ZBP-89 identified a binding site at -245 to -215. Electrophoretic mobility shift assays confirmed that both recombinant and endogenous ZBP-89 and Sp1 bind to this element. The potentiation was abolished in the presence of adenoviral protein E1A. Deletion of the N-terminal domain of ZBP-89 abolished the potentiation mediated by butyrate treatment. This same deletion mutant abolished the ZBP-89 interaction with p300. Cotransfection of p300 with ZBP-89 stimulated the p21(waf1) promoter in the absence of butyrate. p300 co-precipitated with ZBP-89 but not with Sp1, whereas ZBP-89 co-precipitated with Sp1. Together, these findings demonstrate that ZBP-89 also plays a critical role in butyrate activation of the p21(waf1) promoter and reveals preferential cooperation of this four-zinc finger transcription factor with p300.

ZBP-89 promotes growth arrest through stabilization of p53

Transcription factor p53 can induce growth arrest and/or apoptosis in cells through activation or repression of downstream target genes. Recently, we reported that ZBP-89 cooperates with histone acetyltransferase coactivator p300 in the regulation of p21(waf1), a cyclin-dependent kinase inhibitor whose associated gene is a target gene of p53. Therefore, we examined whether ZBP-89 might also inhibit cell growth by activating p53. In the present study, we demonstrate that elevated levels of ZBP-89 induce growth arrest and apoptosis in human gastrointestinal cell lines. The ZBP-89 protein accumulated within 4 h, and the p53 protein accumulated within 16 h, of serum starvation without changes in p14ARF levels, demonstrating a physiological increase in the cellular levels of these two proteins. Overexpression of ZBP-89 stabilized the p53 protein and enhanced its transcriptional activity through direct protein-protein interactions. The DNA binding and C-terminal domains of p53 and the zinc finger domain of ZBP-89 mediated the interaction. A point mutation in the p53 DNA binding domain, R273H, greatly reduced ZBP-89-mediated stabilization but not their physical interaction. Furthermore, ZBP-89 formed a complex with p53 and MDM2 and therefore did not prevent the MDM2-p53 interaction. However, heterokaryon assays demonstrated that ZBP-89 retained p53 in the nucleus. Collectively, these data indicate that ZBP-89 regulates cell proliferation in part through its ability to directly bind the p53 protein and retard its nuclear export. Our findings further our understanding of how ZBP-89 modulates cell proliferation and reveals a novel mechanism by which the p53 protein is stabilized.

Peroxisome proliferator-activated receptor α activation attenuates the inflammatory response to protect the liver from acute failure by promoting the autophagy pathway

Peroxisome proliferator-activated receptor α (PPARα) has been reported to induce a potent anti-inflammatory response. Autophagy is a recently recognized rudimentary cellular response to inflammation and injury. The aim of the present study was to test the hypothesis that PPARα activation mediates autophagy to inhibit liver inflammation and protect against acute liver failure (ALF). PPARα expression during ALF and the impact of PPARα activation by Wy-14 643 on the hepatic immune response were studied in a D-galactosamine/lipopolysaccharide-induced mouse model. Autophagy was inhibited by 3-methyladenine or small interfering RNA (siRNA) against Atg7. In both the mouse model and human ALF subjects, PPARα was significantly downregulated in the injured liver. PPARα activation by pretreatment with Wy-14 643 protected against liver injury in mice. The protective effect of PPARα activation relied on the suppression of inflammatory mechanisms through the induction of autophagy. This hypothesis is supported by the following evidence: first, PPARα activation suppressed proinflammatory responses and inhibited phosphorylated NF-κBp65, phosphorylated JNK and phosphorylated ERK pathways in vivo. Second, protection by PPARα activation was due to the induction of autophagy because inhibition of autophagy by 3-methyladenine or Atg7 siRNA reversed liver protection and inflammation. Third, PPARα activation directly induced autophagy in primary macrophages in vitro, which protected cells from a lipopolysaccharide-induced proinflammatory response. Here, for the first time, we have demonstrated that PPARα-mediated induction of autophagy ameliorated liver injury in cases of ALF by attenuating inflammatory responses, indicating a potential therapeutic application for ALF treatment.

Inhibition of CXCR2 signaling promotes recovery in models of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease characterized by demyelination/remyelination episodes that ultimately fail. Chemokines and their receptors have been implicated in both myelination and remyelination failure. Chemokines regulate migration, proliferation and differentiation of immune and neural cells during development and pathology. Previous studies have demonstrated that the absence of the chemokine receptor CXCR2 results in both disruption of early oligodendrocyte development and long-term structural alterations in myelination. Histological studies suggest that CXCL1, the primary ligand for CXCR2, is upregulated around the peripheral areas of demyelination suggesting that this receptor/ligand combination modulates responses to injury. Here we show that in focal LPC-induced demyelinating lesions, localized inhibition of CXCR2 signaling reduced lesion size and enhanced remyelination while systemic treatments were relatively less effective. Treatment of spinal cord cultures with CXCR2 antagonists reduced CXCL1 induced A2B5+ cell proliferation and increased differentiation of myelin producing cells. More critically, treatment of myelin oligodendrocyte glycoprotein peptide 35-55-induced EAE mice, an animal model of multiple sclerosis, with small molecule antagonists against CXCR2 results in increased functionality, decreased lesion load, and enhanced remyelination. Our findings demonstrate the importance of antagonizing CXCR2 in enhancing myelin repair by reducing lesion load and functionality in models of multiple sclerosis and thus providing a therapeutic target for demyelinating diseases.

Post-embryonic expression of C. elegans microRNAs belonging to the lin-4 and let-7 families in the hypodermis and the reproductive system

MicroRNAs (miRNAs) are regulatory molecules that negatively control gene expression by binding to complementary sequences on target mRNAs. The most thoroughly characterized miRNAs, lin-4 and let-7, direct cell fate determination during the larval transitions in C. elegans and act as key regulators of temporal gene expression. lin-4 and let-7 are founding members of two distinct families of miRNA genes sharing strong sequence homology primarily in the 5' end of the mature miRNAs. In this report, we characterize the temporal and spatial expression patterns of lin-4 and let-7 family members using northern blot analysis and mir::gfp fusion studies. Our results show that lin-4 and let-7 homologues possess distinct temporal and spatial expression patterns during nematode development and that known heterochronic genes regulate their expression. We find that certain lin-4 and let-7 family members display overlapping expression patterns in the hypodermis and the reproductive system, suggesting that combinations of miRNAs from across families may control common developmental events.

Structure of aquaporin-2 vasopressin water channel

Aquaporin-2 (AQP-2) is a vasopressin-regulated water channel in the kidney collecting duct. AQP-2 is selectively permeable to water molecule and is translocated between the apical membrane and subapical endosomes in response to vasopressin. To investigate the localization and structure of the aqueous pathway of the AQP-2 water channel, a series of site-directed mutants was constructed and functionally analyzed. Insertion of N-glycosylation reporter sequence into each hydrophilic loop (HL) indicated that AQP-2 has a six-membrane spanning topology and that insertional mutations in HL-2 or HL-5 do not alter water channel function. Mercury-sensitive site of AQP-2 is located near the second asparagine-proline-alanine (NPA) domain at cysteine 181, but not near the first NPA domain. Replacement of HL-3 or HL-4 with the corresponding part of Escherichia coli glycerol facilitator abolished water channel function without changing plasma membrane expression of the channel protein. Introduction of cysteine residues in His-122, Asn-123, Gly-154, Asp-155, or Asn-156 induced partial mercury sensitivity, and point mutations in asparagine 123 significantly altered water permeability. Our results implicate that the structure of AQP-2 is different from models previously proposed for AQP-1 and that HL-3 and HL-4 are closely located to the aqueous pathway.

Hypoxic repression of STAT1 and its downstream genes by a pVHL/HIF-1 target DEC1/STRA13

DEC1/STRA13 is a bHLH type transcriptional regulator involved with immune regulation, hypoxia response and carcinogenesis. We recently demonstrated that STRA13 interacts with STAT3 in the transcriptional activation of STAT-dependent promoters. Here, we pursue STRA13 involvement in the JAK/STAT pathway by studying its role in STAT1 expression. First, we showed that VHL deficiency or HIF-1 activation resulted in the repression of endogenous STAT1 mediated by STRA13. We then characterized the STAT1 proximal promoter to assess its response to STRA13 by transient coexpression in a luciferase reporter assay. Using sequential truncation and site-directed mutagenesis of the STAT1 promoter with STRA13 deletion constructs, we showed that the STRA13 C-terminal trans-activation domain, which is known to bind HDAC1, mostly determines the repressive activity. Involvement of HDAC activity in STAT1 regulation was validated by TSA inhibition and chromatin immunoprecipitation (ChIP) assay. Thus, we demonstrate that STRA13-mediated repression of STAT1 transcription utilizes an HDAC1-dependent mechanism. Furthermore, we show that targets of unphosphorylated STAT1, such as antigen presenting genes and CASP1, are also repressed by hypoxia possibly through the same STRA13-mediated mechanism. Thus, the newly discovered link between HIF-1 and STAT1 reveals a previously unknown role of STRA13 in hypoxia and carcinogenesis.

ZBP-89, Sp1, and nuclear factor-kappa B regulate epithelial neutrophil-activating peptide-78 gene expression in Caco-2 human colonic epithelial cells

We reported previously that human colonic epithelial cells produce the C-X-C chemokine epithelial neutrophil-activating peptide-78 (ENA-78) and that its expression is up-regulated in ulcerative colitis. The aim of this study was to investigate the transcriptional regulation of ENA-78 gene expression in Caco-2 intestinal epithelial cells. Reporter gene transfection and electrophoretic mobility shift assay studies demonstrated that cooperation between two regions of the ENA-78 promoter were required for maximal gene expression in interleukin-1beta-stimulated Caco-2 cells. Binding of activated p50/p65 nuclear factor-kappaB to nucleotides -82 to -91 was essential for interleukin-1beta-dependent gene transcription, whereas binding of constitutively expressed zinc-requiring nuclear factors to nucleotides -125 to -134 (site A) was required for basal gene expression. Scanning mutagenesis of site A demonstrated overlapping binding elements at this locus. One site (CTCCCCC) bound Sp1 and Sp3, and overexpression of Sp1 (but not Sp3) up-regulated basal ENA-78 transcription. Another site (CCCCTCCCCC) was found to bind the zinc finger nuclear factor ZBP-89, and overexpression of this protein significantly repressed ENA-78 reporter gene activity. This study demonstrates that ENA-78 gene expression in Caco-2 intestinal epithelial cells is subject to complex regulation involving the coordinate binding of ZBP-89, Sp1, and nuclear factor-kappaB to the ENA-78 promoter.

Inhibition of glycogen synthase kinase 3β promotes autophagy to protect mice from acute liver failure mediated by peroxisome proliferator-activated receptor α

Our previous studies have demonstrated that inhibition of glycogen synthase kinase 3β (GSK3β) activity protects mice from acute liver failure (ALF), whereas its protective and regulatory mechanism remains elusive. Autophagy is a recently recognized rudimentary cellular response to inflammation and injury. The aim of the present study was to test the hypothesis that inhibition of GSK3β mediates autophagy to inhibit liver inflammation and protect against ALF. In ALF mice model induced by D-galactosamine (D-GalN) and lipopolysaccharide (LPS), autophagy was repressed compared with normal control, and D-GalN/LPS can directly induce autophagic flux in the progression of ALF mice. Autophagy activation by rapamycin protected against liver injury and its inhibition by 3-methyladenine (3-MA) or autophagy gene 7 (Atg7) small interfering RNA (siRNA) exacerbated liver injury. The protective effect of GSK3β inhibition on ALF mice model depending on the induction of autophagy, because that inhibition of GSK3β promoted autophagy in vitro and in vivo, and inhibition of autophagy reversed liver protection and inflammation of GSK3β inhibition. Furthermore, inhibition of GSK3β increased the expression of peroxisome proliferator-activated receptor α (PPARα), and the downregulated PPARα by siRNA decreased autophagy induced by GSK3β inhibition. More importantly, the expressions of autophagy-related gene and PPARα are significantly downregulated and the activity of GSK3β is significantly upregulated in liver of ALF patients with hepatitis B virus. Thus, we have demonstrated the new pathological mechanism of ALF that the increased GSK3β activity suppresses autophagy to promote the occurrence and development of ALF by inhibiting PPARα pathway.

USP4 inhibits p53 and NF-κB through deubiquitinating and stabilizing HDAC2

Histone deacetylases (HDACs) are major epigenetic modulators involved in a broad spectrum of human diseases including cancers. As HDACs are promising targets of cancer therapy, it is important to understand the mechanisms of HDAC regulation. In this study, we show that ubiquitin-specific peptidase 4 (USP4) interacts directly with and deubiquitinates HDAC2, leading to the stabilization of HDAC2. Accumulation of HDAC2 in USP4-overexpression cells leads to compromised p53 acetylation as well as crippled p53 transcriptional activation, accumulation and apoptotic response upon DNA damage. Moreover, USP4 targets HDAC2 to downregulate tumor necrosis factor TNFα-induced nuclear factor (NF)-κB activation. Taken together, our study provides a novel insight into the ubiquitination and stability of HDAC2 and uncovers a previously unknown function of USP4 in cancers.

Advanced oxidation protein products induce intestine epithelial cell death through a redox-dependent, c-jun N-terminal kinase and poly (ADP-ribose) polymerase-1-mediated pathway

Advanced oxidation protein products (AOPPs), a novel protein marker of oxidative damage, have been confirmed to accumulate in patients with inflammatory bowel disease (IBD), as well as those with diabetes and chronic kidney disease. However, the role of AOPPs in the intestinal epithelium remains unclear. This study was designed to investigate whether AOPPs have an effect on intestinal epithelial cell (IEC) death and intestinal injury. Immortalized rat intestinal epithelial (IEC-6) cells and normal Sprague Dawley rats were treated with AOPP-albumin prepared by incubation of rat serum albumin (RSA) with hypochlorous acid. Epithelial cell death, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit activity, reactive oxygen species (ROS) generation, apoptosis-related protein expression, and c-jun N-terminal kinase (JNK) phosphorylation were detected both in vivo and in vitro. In addition, we measured AOPPs deposition and IEC death in 23 subjects with Crohn's disease (CD). Extracellular AOPP-RSA accumulation induced apoptosis in IEC-6 cultures. The triggering effect of AOPPs was mainly mediated by a redox-dependent pathway, including NADPH oxidase-derived ROS generation, JNK phosphorylation, and poly (ADP-ribose) polymerase-1 (PARP-1) activation. Chronic AOPP-RSA administration to normal rats resulted in AOPPs deposition in the villous epithelial cells and in inflammatory cells in the lamina propria. These changes were companied with IEC death, inflammatory cellular infiltration, and intestinal injury. Both cell death and intestinal injury were ameliorated by chronic treatment with apocynin. Furthermore, AOPPs deposition was also observed in IECs and inflammatory cells in the lamina propria of patients with CD. The high immunoreactive score of AOPPs showed increased apoptosis. Our results demonstrate that AOPPs trigger IEC death and intestinal tissue injury via a redox-mediated pathway. These data suggest that AOPPs may represent a novel pathogenic factor that contributes to IBD progression. Targeting AOPP-induced cellular mechanisms might emerge as a promising therapeutic option for patients with IBD.

Glucagon-like peptide-1 enhances production of insulin in insulin-producing cells derived from mouse embryonic stem cells

Embryonic stem cells (ESCs) can be differentiated into insulin-producing cells by a five-stage procedure involving altering culture conditions and addition of nicotinamide. The amounts of insulin in these cells are lower than those found in pancreatic beta cells. Glucagon-like peptide-1 (GLP-1) induces the differentiation of beta cells from ductal progenitor cells. We examined the possibility of GLP-1, and its long-acting agonist exendin-4, enhancing the differentiation of insulin-producing cells from mouse ESCs (mESCs). A five-stage culturing strategy starting with embryoid bodies (EBs) was used in this study. mRNA for pancreatic duodenal homeobox gene 1 (PDX-1) and neurogenic differentiation (NeuroD) was detected from stage 1, hepatocyte nuclear factor 3 beta (HNF3beta) and insulin 2 from stage 2, Ngn3 and glucose transporter 2 (GLUT2) from stage 3, and insulin 1 and other beta-cell markers, at stages 4-5. Cells at stage 5 secreted C-peptide, being 0.68 +/- 0.01 pmol/10(6) cells per 2 days, and had an immunoreactive insulin content of 13.5 +/- 0.7 pmol/10(6) cells. Addition of GLP-1 (100 nM) and nicotinamide (10 mM) at stage 5 resulted in a 50% and 48% increase in insulin content and C-peptide secretion respectively compared with nicotinamide alone. Glucose-induced insulin secretion was enhanced 4-fold by addition of both growth factors. The GLP-1 receptor was present at all five stages of the culture. Addition of exendin-4 to cells at stage 2 resulted in a 4.9-fold increase in expression of the gene for insulin 1 and a 2-fold increase in insulin content compared with the effect of nicotinamide alone at stage 5. It is concluded that both GLP-1 and exendin-4 enhance the level of expression of insulin in glucose-responsive insulin-producing cells derived from the R1 mESC line.

Cloning and characterization of a type III Na-dependent phosphate cotransporter from mouse intestine

Intestinal and renal absorption of inorganic phosphate (P(i)) is critical for phosphate homeostasis in mammals. We have isolated a cDNA that encodes a type III Na-dependent phosphate cotransporter from mouse small intestine (mPit-2). The nucleotide sequence of mPit-2 predicts a protein of 653 amino acids with at least 10 putative transmembrane domains. Kinetic studies, carried out in Xenopus oocytes, showed that mPit-2 cRNA induces significant Na-dependent P(i) uptake with an apparent Michaelis constant (K(m)) for phosphate of 38 microM. The transport of phosphate by mPit-2 is inhibited at high pH. Northern blot analysis demonstrated the presence of mPit-2 mRNA in various tissues, including intestine, kidney, heart, liver, brain, testis, and skin. The highest expression of mPit-2 in the intestine was found in the jejunum. In situ hybridization revealed that mPit-2 mRNA is expressed throughout the vertical crypt-villus axis of the intestinal epithelium. The presence of mPit-2 in the mouse intestine and its unique transport characteristics suggest that multiple Na-dependent cotransporters may contribute to phosphate absorption in the mammalian small intestine.

Regulation of the human sodium-phosphate cotransporter NaP(i)-IIb gene promoter by epidermal growth factor

The intestinal sodium-phosphate cotransporter (NaP(i)-IIb) plays a major role in intestinal P(i) absorption. Epidermal growth factor (EGF) is involved in the regulation of P(i) homeostasis. However, the role of EGF in intestinal NaP(i)-IIb regulation is not clear. The current studies showed that EGF decreased NaP(i)-IIb mRNA abundance by 40-50% in both rat intestine and Caco-2 cells. To understand the mechanism of this regulation, we cloned the human NaP(i)-IIb gene and promoter region and studied the effect of EGF on NaP(i)-IIb gene transcription. The human NaP(i)-IIb gene has 12 exons and 11 introns. Two transcription initiation sites were identified by primer extension. Additionally, 2.8 kb of the 5'-flanking region of the gene was characterized as a functional promoter in human intestinal (Caco-2) and human lung (A549) cells. Additional studies showed that EGF inhibited promoter activity by 40-50% in Caco-2 cells and that actinomycin D treatment abolished this inhibition. EGF had no effect on promoter activity in lung (A549) cells. We conclude that the human NaP(i)-IIb gene promoter is functional in Caco-2 and A549 cells and that the gene is responsive to EGF by a transcriptionally mediated mechanism in intestinal cells.

Spatiotemporal properties of an evoked population activity in rat sensory cortical slices

We have examined the spatiotemporal properties of ensemble activity, an evoked all-or-none polysynaptic activity in rat neocortical slices. Ensemble activity occurred in cortical slices bathed in normal artificial cerebrospinal fluid (ACSF) and was evoked by a single electrical shock either to the white matter or directly to the cortical tissue. This activity was seen in slices of somatosensory and auditory cortices; in other cortical areas we have not been able to evoke it. The activity developed 10 to 250 ms poststimulus and lasted 280 +/- 120 ms in local field potential (LFP) recordings. Voltage-sensitive dye imaging showed that this activity was an area of activation 0.8 +/- 0.4 mm wide that propagated slowly (11.4 +/- 6.2 mm/s, n = 60, 6 animals) in the horizontal direction. Due to this propagation, the actual duration in the whole tissue may be longer (approximately 400 ms) than that recorded by a single LFP electrode. Ensemble activity produced a low-amplitude optical signal (7-14% of the interictal-like spikes in the same tissue), suggesting a moderate net depolarization of the population. These were very different from hyperexcitable (epileptiform) events in the same tissue that had about 10 times the optical signal amplitude and propagated at 125 +/- 24 mm/s (n = 21, 6 animals). On a global spatial scale (approximately 0.8 mm wide in layers II-III) ensemble activity had a smooth waveform in voltage-sensitive dye signals (population transmembrane potential). On a local scale, field potential recordings showed large fluctuations with complex oscillations and substantial trial-to-trial variation. This suggests that oscillations in cortical circuits occurred only in small clusters of correlated neurons. Ensemble activity was sensitive to the excitation-inhibition balance of the local network. Antagonists of N-methyl-D-aspartate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, and GABAa receptors, and muscarinic agonists and other modest manipulations such as increasing bath concentration of Mg(2+) to 2.5-4 mM (normally at 2 mM), or K(+) to 5-7 mM (normally 3 mM), all significantly reduced the probability of evoking the activity. The metabotropic glutamate receptor agonist, aminocyclopentane-1,3-dicarboxylic acid, blocked the activity at a low concentration (10-15 microM), while the antagonist (R,S)-alpha-methyl-4-carboxyphenylglycine had no effect even at high concentration (240 microM). Our data suggest that locally organized neuronal clusters may play a role in the organization of oscillatory activities in the gamma band and may participate in cortical integration/amplification occurring on a scale of approximately 1 mm x 300 ms.

OLA1 protects cells in heat shock by stabilizing HSP70

The heat-shock response is an evolutionarily conserved cellular defense mechanism against environmental stresses, characterized by the rapid synthesis of heat-shock proteins (HSPs). HSP70, a highly inducible molecular chaperone, assists in refolding or clearance of damaged proteins, thereby having a central role in maintaining intracellular homeostasis and thermotolerance. To date, induction of HSP70 expression has been described extensively at the transcriptional level. However, post-translational regulation of HSP70, such as protein stability, is only partially understood. In this study, we investigated the role of OLA1 (Obg-like ATPase 1), a previously uncharacterized cytosolic ATPase, in regulating the turnover of HSP70. Downregulation of OLA1 in mammalian cells by either RNAi or targeted gene disruption results in reduced steady-state levels of HSP70, impaired HSP70 induction by heat, and functionally, increased cellular sensitivity to heat shock. Conversely, overexpression of OLA1 correlates with elevated HSP70 protein levels and improved thermal resistance. Protein–protein interaction assays demonstrated that binding of OLA1 to the HSP70 carboxyl terminus variable domain hinders the recruitment of CHIP (C-terminus of Hsp70-binding protein), an E3 ubiquitin ligase for HSP70, and thus prevents HSP70 from the CHIP-mediated ubiquitination. These findings suggest a novel molecular mechanism by which OLA1 stabilizes HSP70, leading to upregulation of HSP70 as well as increased survival during heat shock.