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E Lundgren

Publications and source records attributed to E Lundgren.

At least 91 records · Page 5Linked to original sources
PubMed1995

The cytoplasmic C-terminal domain but not the N-terminal domain of latent membrane protein 1 of Epstein-Barr virus is essential for B cell activation.

The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) is essential for EBV-induced immortalization of human primary B cells, transforms rodent fibroblasts and induces the up-regulation of several B cell activation markers when transiently expressed in primary B cells. The biochemical function of LMP-1 is unclear and limited information is available on the involvement of different domains of the protein in B cell activation. The present study describes the characterization of LMP-1 N- and C-terminal deletion mutants in terms of their cell surface distribution and ability to induce activation markers in primary human B cells and in the type I Burkitt's lymphoma cell line DG75. The C-terminal deletion mutant was detected by immunofluorescence via antibodies targeted against an eight amino acid FLAG epitope substituted for the entire predicted cytoplasmic C-terminal domain. Our findings show that N-terminal deletion mutants of LMP-1 are unable to attain their usual patched distribution on the plasma membrane but retain the ability to activate B cells. In contrast, the C-terminal deletion mutant shows the same patched cell surface distribution as wild-type LMP-1 but is unable to activate B cells. The patched distribution of LMP-1 in the plasma membrane is therefore not sufficient nor necessary for the induction of B cell activation and the results rule out patching as a direct mechanism in LMP-1-induced activation. This is the first study addressing the role of the LMP-1 C-terminal domain in lymphocytes and our results show that this domain is essential for B cell activation and therefore likely to be important for the early events of B cell immortalization by EBV.

Antigens, CD↗
PubMed1994

Identification of mRNAs encoding two different soluble forms of the human interferon alpha-receptor.

Transcripts of the human IFN alpha-receptor (IFNAR) gene, lacking the transmembrane (TM) domain were found in human myeloma U266S cells, in addition to the transmembranal IFNAR cDNA. Two different cDNAs encoding such soluble IFNAR forms were identified. Form 1 has a deletion causing a frameshift toward the end of the extracellular (EC) domain predicting a tail of 7 amino acids. Form 2 has two in-frame deletions and conserves most of the intracytoplasmatic domain of IFNAR. The transcripts for the two soluble forms are still found in U266R cells which have lost the transmembranal IFNAR transcript. Human cells seem to have independent mechanisms to synthesize soluble IFN receptors, which may act as competitors outside the cells or carry IFN-mediated functions inside the cell.

Alternative Splicing↗
PubMed1994

Upregulation of bcl-2 by the Epstein-Barr virus latent membrane protein LMP1: a B-cell-specific response that is delayed relative to NF-kappa B activation and to induction of cell surface markers.

An ability of the Epstein-Barr virus latent membrane protein LMP1 to enhance the survival of infected B cells through upregulation of the bcl-2 oncogene was first suggested by experiments involving gene transfection and the selection of stable LMP1+ clones (S. Henderson, M. Rowe, C. Gregory, F. Wang, E. Kieff, and A. Rickinson, Cell 65:1107-1115, 1991). However, it was not possible to ascertain whether Bcl-2 upregulation was a specific consequence of LMP1 expression or an artifact of the selection procedure whereby rare Bcl-2+ cells already present in the starting population might best be able to tolerate the potentially toxic effects of LMP1. We therefore reexamined this issue by using two different experimental approaches that allowed LMP1-induced effects to be monitored immediately following expression of the viral protein and in the absence of selective pressures; activation of the NF-kappa B transcription factor and upregulation of the cell adhesion molecule ICAM-1 were used as early indices of LMP1 function. In the first approach, stable clones of two B-cell lines carrying an LMP1 gene under the control of an inducible metallothionein promoter were induced to express LMP1 in all cells. Activation of NK-kappa B and upregulation of ICAM-1 occurred within 24 h and were followed at 48 to 72 h by upregulation of Bcl-2. In the second approach, we tested the generality of this phenomenon by transiently expressing LMP1 from a strong constitutively active promoter in a range of different cell types. All six B-cell lines tested showed NF-kappa B activation in response to LMP1 expression, and this was followed in five of six lines by expression of ICAM-1 and Bcl-2. In the same experiments, all three non-B-cell lines showed NF-kappa B activation and ICAM-1 upregulation but never any effect upon Bcl-2. We therefore conclude that Bcl-2 upregulation is part of the panoply of cellular changes induced by LMP1 but that the effect is cell type specific. Our data also suggest that whilst NF-kappa B may be an essential component of LMP1 signal transduction, other cell-specific factors may be required to effect some functions of the viral protein.

Antigens, CD↗
PubMed1993

Modifications of transthyretin in amyloid fibrils: analysis of amyloid from homozygous and heterozygous individuals with the Met30 mutation.

The finding of individuals homozygous for FAP I (familial amyloidotic polyneuropathy, transthyretin TTRMet30) with amyloid deposits in the vitreous body, gave us access to a unique material lacking wild type transthyretin and contaminating proteins. Amyloid TTR is modified in several ways. Besides the full-length protein and its dimer form, two smaller bands were identified by SDS-PAGE and protein sequencing. One corresponded to a peptide starting at amino acid Thr49, the other was a mixture of two peptides starting at positions 1 and 3 in a 3:1 ratio. Upon reduction the amount of the TTR dimer decreased, the monomer amount increased, and the resulting monomers became available for carboxymethylation. Moreover, the mobility of the small band, which includes Cys10, increased upon reduction. This cysteine seemed to be involved in an interchain disulfide bridge both between intact TTR molecules and between small fragments. The same pattern was found in heterozygous fibril material although smaller amounts of the truncated peptides were found. Fibrils were formed both from normal and mutated TTR in heterozygotes. The significance of our results for amyloid formation is discussed.

Amino Acid Sequence↗
PubMed1993

Intracellular calcium oscillations induced in a T-cell line by a weak 50 Hz magnetic field.

Applied weak magnetic fields have been shown to affect cellular activity on several levels, but the mechanisms involved remain elusive. We have decided to study an early signal transduction event in the human T cell line Jurkat; oscillations of free [Ca2+]i, of the type seen by crosslinking the CD3 complex. Cells were exposed to a 50 Hz, 0.1 mT, sinusoidal magnetic field while intracellular free calcium was measured in individual cells, using fura-2 as a probe. An acute response was observed with oscillatory increases in [Ca2+]i, which subsided when the field was turned off. The effect of the magnetic field on [Ca2+]i was comparable to that achieved by an anti-CD3 monoclonal antibody.

Antibodies, Monoclonal↗
PubMed1993

Differential regulation of LFA-1 and ICAM-1 on human primary B-lymphocytes.

Changes in adhesive properties play important regulatory roles in activation and differentiation of B-cells. To better understand the regulation of interactions between B-cells and other cells during the immune response, we have studied surface expression of the adhesion molecules LFA-1 (CD11a/CD18) and ICAM-1 (CD54). Both adhesion molecules were upregulated during B-cell activation. However, upon stimulation with anti-IgM and IL-4, ICAM-1 levels started to increase within 12 hr, while LFA-1 levels did not start to increase until after 36 hr. When B-cells were stimulated with the PKC activator PDB and a calcium ionophore, ICAM-1 levels, but not LFA-1 levels, increased. Only if these activators were removed after around 24 hr of activation and the cells were recultured in fresh medium was there an eightfold induction of LFA-1. Such reculturing in fresh medium led, however, to decreased ICAM-1 levels.

Antibodies, Monoclonal↗
PubMed1993

Predicting severity of trauma by admission white blood cell count, serum potassium level, and arterial pH.

Traumatized patients frequently have leukocytosis, hypokalemia, and acidosis. The purpose of this study was to determine whether the admission serum potassium level (K+), white blood cell count (WBC), and arterial pH predicted the severity of injury in trauma patients. The injury severity score (ISS), total length of stay in the hospital (tLOS), and length of stay in the intensive care unit (LOS-ICU) were used to measure the severity of the injury. The charts of 156 consecutive trauma patients admitted to a level II trauma center were reviewed. Acidosis (arterial pH < 7.35) was associated with an increased mean ISS, tLOS, and LOS-ICU. Leukocytosis (WBC > or = 10,500/mm3) correlated with a higher mean ISS, and LOS-ICU. Patients with hypokalemia (K+ < 3.6 mEq/L) had an increased mean ISS and tLOS. Our findings suggest that the admission white blood cell count, serum potassium level, and arterial pH have a predictive value as to the severity of injury.

Acidosis↗
PubMed1993

Diagnostic radioimmunoassay and DNA-analysis in Swedish and Japanese patients with familial amyloidotic polyneuropathy. Homozygosity for the TTR met30 gene.

Eighteen Swedish patients with familial amyloidotic polyneuropathy were tested for the met30 mutation of the transthyretin (TTR) (prealbumin) gene by RFLP analysis of genomic DNA using the restriction enzyme NsiI. The results confirmed previous findings that the Swedish variant of familial polyneuropathy has the same valine by methionine substitution at position 30, as seen in patients with FAP from Japan, Portugal or patients of Swedish descent from USA. However, two of the patients were homozygous, totally lacking the wild type allele. Measurable serum values for the variant transthyretin (TTR) was detected with a RIA-method in all the 18 Swedish FAP patients studied with a mean concentration of 12.1 +/- 5.1 (SD) mg/100 ml, (11.0 +/- 4.1 when the two homozygotes were excluded). In 45 Japanese patients the mean was 9.2 +/- 2.7 mg/100 ml. The variant TTR was not detected in the healthy controls. The value for the variant TTR was nearly twice that high in the two homozygous patients, 21.14 and 21.16 mg/100 ml, respectively. There was no correlation between the serum levels of variant TTR and the duration of disease or levels of serum albumin in the FAP-patients.

Adolescent↗
PubMed1993

Transient expression of the Epstein-Barr virus LMP1 gene in B-cell chronic lymphocytic leukemia cells, T cells, and hematopoietic cell lines: cell-type-independent-induction of CD23, CD21, and ICAM-1.

The Epstein-Barr virus (EBV) genome has recently been detected in various non-B cell neoplasms, including various T-cell leukemias and in Reed-Sternberg cells of Hodgkin's disease, but the contribution of EBV genes to the transformed phenotype remains unclear. We have investigated the possible effect which the EBV genes LMP1 and EBNA2, of which the expression has been reported in non-B cell neoplasms, may have on a variety of cell types. The LMP1 and EBNA2 genes were transiently expressed from heterologous promoters in two human T-cell lines (HPB-ALL and Jurkat), two human cell lines of the myeloid lineage (K562 and U937), one type I Burkitt's lymphoma cell line (Rael) and in human primary T cells and B-cell chronic lymphocytic leukemia cells. The cell surface expression of CD23, CD21, ICAM-1 and LFA-1 was monitored on transfected cells. In the cell lines, except U937, the surface antigens CD21 and ICAM-1 were upregulated in a dose-dependent and transient manner by the transient expression of LMP1, and EBNA2 slightly enhanced the effects of LMP1 on CD23 and CD21 upregulation. LMP1 also induced increased CD21, ICAM-1 and LFA-1 surface expression on transfected primary T-cells, and CD21 and ICAM-1 in four of five B-cell chronic lymphocytic leukemias tested. Finally, LMP1 transient expression caused increased cell size of the primary T cells and responding B-cell chronic lymphocytic leukemia cells. Our results strongly suggest that LMP1 can trigger specific responses in a variety of white cell types and thus is probably contributing to the phenotype of EBV-positive tumor cells not only in the B-cell lineage.

Antigens, Viral↗