Stargazin and AMPA receptor membrane expression is increased in the somatosensory cortex of Genetic Absence Epilepsy Rats from Strasbourg

Absence-like seizures in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model are believed to arise in hyperexcitable somatosensory cortical neurons, however the cellular basis of this increased excitability remains unknown. We have previously shown that expression of the Transmembrane AMPA receptor Regulatory Protein (TARP), stargazin, is elevated in the somatosensory cortex of GAERS. TARPs are critical regulators of the trafficking and function of AMPA receptors. Here we examine the developmental expression of stargazin and the impact this may have on AMPA receptor trafficking in the GAERS model. We show that elevated stargazin in GAERS is associated with an increase in AMPA receptor proteins, GluA1 and GluA2 in the somatosensory cortex plasma membrane of adult epileptic GAERS. Elevated stargazin expression is not seen in the epileptic WAG/Rij rat, which is a genetically distinct but phenotypically similar rat model also manifesting absence seizures, indicating that the changes seen in GAERS are unlikely to be a secondary consequence of the seizures. In juvenile (6 week old) GAERS, at the age when seizures are just starting to be expressed, there is elevated stargazin mRNA, but not protein expression for stargazin or the AMPA receptor subunits. In neonatal (7 day old) pre-epileptic GAERS there was no alteration in stargazin mRNA expression in any brain region examined. These data demonstrate that stargazin and AMPA receptor membrane targeting is altered in GAERS, potentially contributing to hyperexcitability in somatosensory cortex, with a developmental time course that would suggest a pathophysiological role in the epilepsy phenotype.

Differential coding potential of ADAM22 mRNAs

ADAM22 is one of three catalytically inactive ADAM family members highly expressed in the brain. Preliminary functional studies suggest possible roles in epilepsy and myelination. We report an additional eight new splice variants of human ADAM22. Analysis of the altered splicing patterns of ADAM22 mRNAs in glioma allows us to suggest alternate splicing patterns in normal brain compared to glioma may represent differential use of exon 32. We also report diversity in the 5' leader sequences of ADAM22 mRNAs as a consequence of alternate transcriptional initiation sites. ADAM22 has an additional transcriptional initiation element producing transcripts lacking the exon 1 sequence including the signal peptide. Variable transcriptional initiation in exon 1 produces a range of ADAM22 5' leader sequence lengths, all of which are significantly longer than those described in NCBI reference sequences. Longer 5' leader sequences contain a second upstream AUG codon which acts to inhibit ADAM22 translation.

Phase I dose-escalation and pharmacokinetic study of a novel folate analogue AG2034

The novel folate analogue AG2034, which was designed as an inhibitor of GARFT (glycinamide ribonucleotide formyltransferase), was evaluated in this phase I study under the auspices of The Cancer Research Campaign, UK. AG2034 blocks de novo purine synthesis through inhibition of GARFT. A total of 28 patients with histologically proven intractable cancers were enrolled. AG2034 was administered as a short intravenous infusion once every 3 weeks. 8 dose levels ranging from 1-11 mg/m(2)were evaluated with patients receiving up to 6 cycles. Dose-limiting toxicities in the form of mucositis, diarrhoea and vomiting were observed at doses of 6 mg/m(2)and above. Significant levels of thrombocytopenia, neutropenia and anaemia were also recorded. Other sporadic toxicities included fatigue and myalgia. The MTD with this schedule of AG2034 was 5 mg/m(2). Most side effects occurred more frequently with cumulative dosing. In keeping with this, pharmacokinetic analysis revealed evidence of drug accumulation. The AG2034 AUC(0-24)increased by a median of 184% (range 20-389%) from cycle 1 to 3 in all 10 patients examined. No objective antitumour responses were observed in the study.

Differential ability of SOCS proteins to regulate IL-6 and CSF-1 induced macrophage differentiation

M1/WT4 cells, derived from the murine myeloid leukemic M1 cells by over-expression of the receptor for CSF-1, were transfected with expression vectors encoding SOCS-1, SOCS-2, SOCS-3 or Cis-1. The differentiation response to CSF-1 and IL-6 was analyzed in the resulting cell lines. Myeloid differentiation in response to CSF-1 was not affected by any of the SOCS proteins, whereas the IL-6-mediated differentiation was inhibited by SOCS-1 and SOCS-3 and slightly delayed by SOCS-2 expression. In M1/WT4 cells IL-6 causes strong tyrosine phosphorylation of STAT3, whereas the response to CSF-1 is weaker. The expression of the SOCS proteins had no effect on CSF-1 mediated STAT3 tyrosine phosphorylation; however, SOCS-1 and SOCS-3 reduced the tyrosine phosphorylation of STAT3 in response to IL-6 but did not abolish it. It appears, therefore, that SOCS-1, -2 and -3 and Cis-1 do not inhibit tyrosine kinase activity involved in CSF-1 mediated cell differentiation, whereas SOCS-1 and -3 are inhibiting kinase activity required for IL-6-mediated differentiation.

STAT3 forms stable homodimers in the presence of divalent cations prior to activation

We present evidence that the transcription factor STAT3, derived from uninduced cells, can form stable homodimers, which are independent of the tyrosine phosphorylation status of the protein. The strong interaction, which is resistant to many denaturing agents, is dependent on the presence of divalent cations. The presence of the homodimer was initially observed in immunoprecipitates of STAT3 and was detected upon fractionation of cell lysates. These dimers are different in structure from dimers observed after cytokine stimulation of cells, which results in tyrosine phosphorylation of STAT3 and dimerization involving the SH2 domain of STAT3.

CSF-1 and interferon-gamma act synergistically to promote differentiation of FDC-P1 cells into macrophages

FDC-P1 cells expressing the wildtype CSF-1 receptor, FDwtfms, differentiate into macrophages during incubation with CSF-1. This response is amplified in the presence of interferon-gamma. Cells expressing the 807F mutant receptor, 807F cells, proliferate in response to CSF-1 and do not differentiate. However, in response to CSF-1 and interferon-gamma they differentiate as well. CSF-1 causes the activation of STAT proteins in FDwtfms cells, but not in 807F cells. Cellular differentiation correlates with a sustained activation of STAT1 and STAT3 in response to interferon-gamma over at least 40 hours. However, interferon-gamma alone did not cause differentiation of cells expressing either receptor. Other defects in response to CSF-1 of the 807F cells, such as lack of PLC gamma 2 activation, were not complemented by co-incubation of the cells with CSF-1 and interferon-gamma. It appears that a combination of signaling pathways are activated by CSF-1 and interferon-gamma which caused the shift of response from proliferation to differentiation in the 807F cells and an enhanced differentiation in the FDwtfms cells.

Requirement for Y706 of the murine (or Y708 of the human) CSF-1 receptor for STAT1 activation in response to CSF-1

Using FDC-P1 derived cell lines which ectopically express either the wild type or mutant forms of the murine CSF-1 receptor in which individual tyrosine residues have been replaced with phenylalanine, we analysed the requirement for tyrosine residues of the receptor for the activation of STAT proteins in response to CSF-1. We found Y706 to be required for efficient activation of STAT1. The activation of STAT3 was not affected by the mutation of Y706 to phenylalanine. The addition of phosphopeptides spanning Y708 of the human CSF-1 receptor (identical with the sequence surrounding Y706 of the murine receptor) to electrophoretic mobility shift assays led to competition of the formation of STAT1 containing complexes, SIF-B and SIF-C with the DNA probe. These phosphopeptides did, however, not affect the formation of the STAT3 containing complex, SIF-A, with the probe. Replacement of Y807 with phenylalanine led to a complete block of activation of all STAT proteins in response to CSF-1, however, this phosphotyrosine does not appear to represent a STAT binding site of the receptor as a phosphopeptide spanning Y809 of the human CSF-1 receptor could not compete any STAT/DNA complex formation in electrophoretic mobility shift assays.

Formation of STAT5-containing DNA binding complexes in response to colony-stimulating factor-1 and platelet-derived growth factor

Colony-stimulating factor (CSF-1) activates several members belonging to the STAT (signal transducers and activators of transcription) family of transcription factors. We investigated the DNA binding complexes activated by CSF-1 in several cell lines and compared them with complexes activated by platelet-derived growth factor and interleukin 3. Our results indicate that the SIF-A complex activated by CSF-1 and platelet-derived growth factor may contain STAT3/STAT5 heterodimers binding to the high affinity SIF binding site, m67. In addition, both growth factors activate one or several STAT5-containing protein complexes binding to the prolactin-inducible element, PIE. The formation of these complexes was cell type and growth factor specific. Interleukin 3 activated only PIE binding complexes containing STAT5A and STAT5B and did not activate m67 binding complexes. It appears, therefore, that STAT5 cannot bind to m67 as a homodimer, but it can bind if it is dimerized with STAT3, whereas it can bind to the PIE element without being either complexed with STAT3 or any other known STAT protein, possibly as a homodimer or as STAT5A/STAT5B heterodimer. However, in addition, STAT5 may heterodimerize with other proteins and form novel PIE binding complexes.

Aberrant activation of JAK/STAT pathway components in response to G-CSF, interferon-alpha/beta and interferon-gamma in NFS-60 cells

There is evidence that the cellular responses to cytokines, such as granulocyte colony stimulating factor (G-CSF) and interferons, depend on prior activation of components of the JAK/STAT signalling pathway. We report here that the myeloid cell line NFS-60 shows aberrant JAK/STAT signalling yet elicits expected biological responses to G-CSF and interferons-alpha/beta and gamma. Instead of increased phosphorylation of JAK1 and JAK2 in response to G-CSF and interferon-gamma, and JAK1 and Tyk2 in response to interferon-alpha/beta, we observed only an increase of phosphorylation of Tyk2 in response to all of these cytokines in NFS-60 cells. The subset of STAT proteins being activated in response to these cytokines was unusual as well. G-CSF activated STAT3 and STAT5A, whereas interferons activated, in addition to STAT1 and STAT5 other, as yet unidentified, DNA binding proteins. However, NFS-60 cells show normal biological responses to these cytokines, such as proliferation in response to G-CSF, and reduction of proliferation, induction of an anti-viral response and induction of specific genes in response to interferons.

Colony-stimulating factor 1-induced STAT1 and STAT3 activation is accompanied by phosphorylation of Tyk2 in macrophages and Tyk2 and JAK1 in fibroblasts

Colony-stimulating factor 1 (CSF-1) causes the activation of STAT1 and STAT3 transcription factors in bone marrow macrophages (BMM), in the macrophage cell line BAC1.2F5, and in fibroblasts that express the wild-type receptor for CSF-1. Fibroblasts expressing a mutant receptor in which the tyrosine 809 is replaced with phenylalanine do not activate STAT proteins in response to CSF-1. The activation of the STAT proteins in BMM is accompanied by tyrosine phosphorylation of Tyk2. In fibroblasts, the activation of the STAT proteins is accompanied by tyrosine phosphorylation of Tyk2 and JAK1. We propose that these JAK kinases are subjected to very rapid phosphorylation in response to CSF-1, followed by rapid dephosphorylation. Furthermore, we propose that kinases other than JAK kinase may be involved in the phosphorylation of the STAT proteins in response to CSF-1.

Regulation of the urokinase gene by the retinoblastoma protein

The promoter of the human urokinase plasminogen activator (uPA) gene contains a sequence identical with the retinoblastoma control element (RCE) of the murine c-fos gene, as well as several Sp1 binding sites. In a number of cell lines, the uPA promoter is activated during enforced expression of the retinoblastoma protein, pRB. Electrophoretic mobility-shift assays revealed that the RCE sequence of the uPA gene forms only one specific DNA-protein complex that does not contain pRB. The formation of the RCE-protein complex can be inhibited by 20 molar excess of the unlabeled RCE sequences and by 5 molar excess of the unlabeled E2F binding site. The RCE of the human uPA gene interacts specifically with a protein, which appears to be distinct from members of the E2F family of proteins, Sp1, ATF2, and Elf-1, which are all transcription factors shown to be regulated by pRB.

Oral enoxacin for infection prevention in adults with acute nonlymphocytic leukemia. The Enoxacin Prophylaxis Study Group

A randomized, double-blind, placebo-controlled trial was conducted in eight hematologic units to determine the efficacy and safety of oral enoxacin for infection prevention in adult patients with acute nonlymphocytic leukemia. One hundred nineteen patients undergoing remission induction or consolidation chemotherapy were enrolled; 62 of them received enoxacin (400 mg orally every 12 h). Patients received antifungal prophylaxis with oral mycostatin (1,000,000 U four times daily) or clotrimazole (1 troche five times daily). Analysis was performed on an intent-to-treat basis. There was no significant difference between groups in race, age, or type and stage of leukemia, but there were more males in the placebo group (P = 0.073 [Fisher's exact test]). Fewer enoxacin patients had gram-negative bacteremia (1 versus 14 [P < 0.001]), gram-negative infection at any site (2 versus 19 [P < 0.001]), or bacterial and/or fungal infection (17 versus 26 [P = 0.056]). There was no significant difference in the number of patients with gram-positive infection at any site (12 versus 16), gram-positive bacteremia (9 versus 10), deep fungal infection (6 versus 2), death (2 versus 3), other antimicrobial therapy required (48 versus 48), therapy with amphotericin B (15 versus 7 [P = 0.105]), any adverse event (45 versus 36), or any study drug-associated adverse events (13 versus 6). Logistic regression confirmed (odds ratios and 95% confidence intervals are given in parentheses) that enoxacin reduced the risk of gram-negative infection (0.07; 0.01 to 0.30), especially gram-negative bacillary bacteremia (0.05; 0.01 to 0.37), without altering the risk of gram-positive bacterial (0.63; 0.26 to 1.5), deep fungal (2.57; 0.47 to 13.9), or Clostridium difficile (1.16; 0.3 to 4.56) infection. The median time to the onset of fever of more than or equal 102.8 F (39.3 degree C) was 32 days for the enoxacin group versus 15 days for patients receiving placebo (P=0.0007 [Wilcoxon test]). In patients with acute nonlymphocytic leukemia, oral enoxacin prevents gram-negative infections, delays the onset of fever, does not alter the incidence of gram-positive or proven deep fungal infections, and is well tolerated.