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Biomedical subjects

J Foerster

Publications and source records attributed to J Foerster.

At least 19 recordsLinked to original sources
PubMed2001

Age-related increase of frequency of a new, phenotypically distinct subpopulation of human peripheral blood T cells expressing lowered levels of CD4.

Aging is associated with modifications of T-cell phenotype and function, leading to impaired activation in response to both new and recall antigens. It is not known if T-cell activation results in elimination of a number of the CD4 molecules from the cell surface, as is the case with CD3/T-cell receptor complexes, or how aging influences the process. The T cells of young and elderly donors with reduced expression of CD4 were examined to see whether these cells exhibit other phenotypic features suggesting their active state. It was found that T lymphocytes expressing CD4 can be divided into 2 semidiscrete subpopulations: the major (CD4(+)) population, in which the level of expression of CD4 is constant and high, and a minor population (CD4(lo)), in which the expression of CD4 can be up to an order of magnitude lower than on the CD4(+) cells. The proportion of CD4(lo) cells is age dependent and highly variable in the apparently healthy human population, with the expression of CD4 ranging from around 10% of all peripheral blood lymphocytes in the young to more than 30% in the elderly. Lowered expression of CD4 is correlated with a reduced expression of CD3, as well as with a decreased amount of CD28 and CD95Fas. Activation of CD4(lo) cells is suggested by their expression of CD25 and increased amounts of HLA-DR. Phenotypic characteristics of the CD4(lo) T-cell subpopulation suggest that it might be formed by (perhaps chronically) activated, temporarily apoptosis-resistant cells, possibly accumulating in the elderly. (Blood. 2001;98:1100-1107)

Adult↗
PubMed2001

MID1, mutated in Opitz syndrome, encodes an ubiquitin ligase that targets phosphatase 2A for degradation.

The gene MID1, the mutation of which causes X-linked Opitz G/BBB syndrome (OS, MIM 300000), encodes a microtubule-associated protein (MAP). We show that mutation of MID1 leads to a marked accumulation of the catalytic subunit of protein phosphatase 2A (PP2Ac), a central cellular regulator. PP2Ac accumulation is caused by an impairment of a newly identified E3 ubiquitin ligase activity of the MID1 protein that normally targets PP2Ac for degradation through binding to its alpha4 regulatory subunit in an embryonic fibroblast line derived from a fetus with OS. Elevated PP2Ac causes hypophosphorylation of MAPs, a pathological mechanism that is consistent with the OS phenotype.

Animals↗
PubMed1999

Interferon consensus sequence binding protein and interferon regulatory factor-4/Pip form a complex that represses the expression of the interferon-stimulated gene-15 in macrophages.

Interferon consensus sequence binding protein (ICSBP), a transcription factor of the interferon (IFN) regulatory factor (IRF) family, binds to the IFN-stimulated response element (ISRE) in the regulatory region of IFNs and IFN-stimulated genes (ISG). To identify target genes, which are deregulated by an ICSBP null-mutation in mice (ICSBP-/-), we have analyzed transcription of an ISRE-bearing gene, ISG15. We have found that although ISG15 expression is unchanged in B cells, it is upregulated in macrophages from ICSBP-/- mice. Three factors, ICSBP, IRF-2, and IRF-4/Pip interact with the ISRE in B cells, however only ICSBP and IRF-4/Pip were found to bind this sequence in macrophages of wild-type mice. Although IRF-4 was considered to be a lymphoid-specific factor, we provide evidence for its role in macrophage gene regulation. Our results suggest that the formation of cell-type-specific heteromeric complexes between individual IRFs plays a crucial role in regulating IFN responses.

Animals↗
PubMed1999

Altered development and cytokine responses of myeloid progenitors in the absence of transcription factor, interferon consensus sequence binding protein.

Mice deficient for the transcription factor, interferon consensus sequence binding protein (ICSBP), are immunodeficient and develop disease symptoms similar to human chronic myeloid leukemia (CML). To elucidate the hematopoietic disorder of ICSBP(-/-) mice, we investigated the growth, differentiation, and leukemogenic potential of ICSBP(-/-) myeloid progenitor cells in vitro, as well as by cell-transfers in vivo. We report that adult bone marrow, as well as fetal liver of ICSBP-deficient mice harbor increased numbers of progenitor cells, which are hyperresponsive to both granulocyte macrophage colony-stimulating factor (GM-CSF) and G-CSF in vitro. In contrast, their response to M-CSF is strongly reduced and, surprisingly, ICSBP(-/-) colonies formed in the presence of M-CSF are mostly of granulocytic morphology. This disproportional differentiation toward cells of the granulocytic lineage in vitro parallels the expansion of granulocytes in ICSBP(-/-) mice and correlates with a 4-fold reduction of M-CSF receptor expressing cells in bone marrow. Cell transfer studies showed an intrinsic leukemogenic potential and long-term reconstitution capability of ICSBP(-/-) progenitors. Further experiments demonstrated strongly reduced adhesion of colony-forming cells from ICSBP(-/-) bone marrow to fibronectin. In summary, ICSBP(-/-) myeloid progenitor cells share several abnormal features with CML progenitors, suggesting that the distal parts of signaling pathways of these two disorders are overlapping.

Adult↗
PubMed1999

The Opitz syndrome gene product, MID1, associates with microtubules.

Opitz syndrome (OS) is a genetically heterogeneous disorder characterized by defects of the ventral midline, including hypertelorism, cleft lip and palate, heart defects, and mental retardation. We recently identified the gene responsible for X-linked OS. The ubiquitously expressed gene product, MID1, is a member of the RING finger family. These proteins are characterized by an N-terminal tripartite protein-protein interaction domain and a conserved C terminus of unknown function. Unlike other RING finger proteins for which diverse cellular functions have been proposed, the function of MID1 is as yet undefined. By using the green fluorescent protein as a tag, we show here that MID1 is a microtubule-associated protein that influences microtubule dynamics in MID1-overexpressing cells. We confirm this observation by demonstrating a colocalization of MID1 and tubulin in subcellular fractions and the association of endogenous MID1 with microtubules after in vitro assembly. Furthermore, overexpressed MID1 proteins harboring mutations described in OS patients lack the capability to associate with microtubules, forming cytoplasmic clumps instead. These data give an idea of the possible molecular pathomechanism underlying the OS phenotype.

DNA Mutational Analysis↗
PubMed1999

The upregulation of TNF alpha production is not a generalised phenomenon in the elderly between their sixth and seventh decades of life.

The aim of this paper was to analyse the link between the intensity of tumor necrosis factor alpha (TNF alpha) production and the health status of the elderly and to find out whether the age between sixty and seventy is a 'turning point' for the changes in the production of this cytokine. Fifty elderly volunteers (age range: 60-70), twenty-five middle-aged (age range: 36-59) and fifty young (age range: 20-35) were enrolled into the study. Their health status was graded as 'healthy' and 'almost-healthy'. The level of TNF alpha was determined by bioassay, the activity of the TNF alpha gene was analysed in non-stimulated PBMC by the RT-PCR method. The results showed that the production of TNF alpha in the 'healthy' elderly people is not upregulated until the age of sixty-seventy. The 'almost-healthy' elderly are characterised by a higher release of TNF alpha from the cultures of non- and stimulated PBMC and an activation of the TNF alpha gene in the non-stimulated PBMC. Summarising, our results indicate that the deterioration of health status is a prerequisite for an exaggerated TNF alpha production by peripheral blood mononuclear cells of people between the sixth and seventh decades of life.

Adult↗
PubMed1998

Increase of interleukin 6 and decrease of interleukin 2 production during the ageing process are influenced by the health status.

The ageing process is accompanied by the disregulation of interleukin 2 (IL2) and interleukin 6 (IL6) production. In our paper, we asked whether the age between 60 and 70 years is a turning point for the disregulation of both IL2 and IL6 production. Fifty volunteers 60-70 years old, 25 aged 36-59, and 50 of 20-35 years old were enrolled into the study. Their health status was graded according to the criteria of the Senieur Protocol (SP) as 'healthy' and 'almost-healthy'. The cytokines level was determined in the sera of the volunteers. Moreover, the spontaneous release of IL6 by peripheral blood mononuclear cells (PBMC) and the activity of the IL6 gene in non-stimulated PBMC were also analysed. Cytokine levels were measured by biological assays, mRNA for IL6 was detected by RT-PCR method. The results showed that the production of IL2 is not disregulated in the 'healthy' people until the age of 60-70. People not fulfilling all SP criteria are characterised by a lower level of IL2 in the sera. The overproduction of IL6 into the sera and supernatants from non-stimulated PBMC and PBL as well as the activation of IL6 gene start between the ages 36 and 59 and is more pronounced in the 'almost-healthy'.

Adult↗
PubMed1997

Functions of conserved cysteines of soluble guanylyl cyclase.

Soluble guanylyl cyclase (sGC), a heme-containing heterodimeric enzyme, is stimulated by NO and catalyzes the formation of the intracellular signaling molecule cGMP. Cysteine residues of sGC have been considered to be important as they were thought to play a significant role in the regulation of the enzyme. The aim of this study was to investigate the possible function of conserved cysteine residues of sGC. Fifteen conserved cysteine residues on sGC were point-mutated to serine, using site-directed mutagenesis. All of the resulting recombinant enzymes were able to synthesize cGMP. Mutation of two cysteines located in the N-terminal, putative heme-binding region of the beta1 subunit yielded proteins that were insensitive to NO. Spectrophotometric analysis of the NO-insensitive mutants purified from Sf9 cells revealed a loss of the prosthetic heme group. Both mutants could be reconstituted with heme and, as a consequence, NO sensitivity of the mutants was restored. Our data show that mutation of two cysteines of the beta1 subunit (Cys-78 and Cys-214) reduces the affinity of sGC for heme. Mutation of the corresponding cysteines on the alpha1 subunit did not alter NO responsiveness, indicating that heme-binding is mainly a feature of the N-terminal domain of the beta1 subunit.

Animals↗
PubMed1997

Overactivity of tumor necrosis factor-alpha but not interleukin 6 is associated with low natural killer cytotoxic activity in the elderly.

In this paper we asked whether the increased production of two proinflammatory cytokines-tumor necrosis factor-alpha (TNF alpha) and interleukin-6 (IL6) in the absence of the inflammatory stimulus, a phenomenon frequently occurring in the elderly, may contribute to the decrease of natural killer (NK) cytotoxic activity. NK cell activity is a part of a nonspecific immunity directed against infected and transformed cells. We measured the levels of bioactive TNF alpha and IL6 during cytotoxic NK reactions and analyzed the effect of neutralizing monoclonal antibodies anti-TNF alpha and anti-IL6 on the outcome of cytotoxic reaction. Bioactive TNF alpha was produced in higher amounts during cytotoxic reactions of the elderly with low NK activity in comparison with its production by the elderly with high NK activity. Anti-TNF alpha decreased already low cytotoxic responses of the elderly while not having an effect on the cytotoxic potential of high responders. More of the bioactive IL6 was released during cytotoxic reactions of the elderly as compared with young people. There was, however, no relation between the height of NK cytotoxic activity and the amount of IL6. Our results suggest that the increased level of TNF alpha seen in the elderly low NK responders may pose a compensatory mechanism, necessary to keep the highest possible level of NK responses. The increased bioactivity of IL6 during NK reaction of the elderly does not seem to participate in the regulation of the level of NK cytotoxic activity.

Adult↗
PubMed1996

A functional heme-binding site of soluble guanylyl cyclase requires intact N-termini of alpha 1 and beta 1 subunits.

Soluble guanylyl cyclase, a heterodimeric enzyme, is the most important intracellular target for the signalling molecule nitric oxide (NO). NO stimulates the enzyme by binding to a prosthetic heme group. The identity of the axial heme ligand, however, is still unknown. Here we show that guanylyl cyclase mutated at the residue His 105 on the beta 1 subunit, a mutant that we have shown before to contain no heme after purification [Wedel, B., Humbert, P., Harteneck, C., Foerster, J., Malkewitz, J., Böhme, E., Schultz, G. & Koesling, D. (1994) Proc. Natl Acad. Sci. USA 91, 2592-2596] can be reconstituted with heme. The reconstituted mutant remains NO-insensitive and displays an ultraviolet absorption spectrum consistent with an altered axial coordination. Thus, this residue is a strong candidate for the axial heme-ligating residue and appears to be necessary for NO stimulation. Apart from the axial heme ligand, the role of the enzyme's two subunits, alpha 1 and beta 1, in heme binding has not been clarified to date. To address this question, we purified mutant heterodimers in which the non-conserved amino termini of either alpha 1 (131 residues deleted), or beta 1 (64 residues) have been deleted. These deletion mutants had previously been found to be marginally (alpha 1 truncated) or not at all NO sensitive (beta 1 truncated) in cytosolic fractions [Wedel, B., Harteneck, C., Foerster, J., Friebe, A., Schultz, G. & Koesling, D. (1995) J. Biol. Chem. 270, 24871-24875]. Here, we show that the purified enzyme truncated on alpha 1 has a significantly reduced capacity to bind heme which explains the reduced NO sensitivity. By contrast, the beta 1-truncated enzyme binds an amount of heme comparable to the wild type but is only marginally NO-responsive and displays a shift in the heme ultraviolet absorption maximum indicative of altered heme coordination. In conclusion, the heme binding site of soluble guanylyl cyclase requires the presence of both subunits in full length to be able to bind wild-type quantities of heme and to be capable of mediating the NO-heme-induced stimulation. Despite some structural similarity, both subunits appear to participate differently in NO-heme-mediated enzyme regulation.

Animals↗
PubMed1995

Functional domains of soluble guanylyl cyclase.

Soluble guanylyl cyclase is a heterodimer consisting of an alpha and beta subunit and stimulation occurs upon binding of NO to a prosthetic group. Little is known about the localization of catalytic and regulatory domains within the subunits of soluble guanylyl cyclase. We used deletion mutagenesis to identify the regions of alpha 1 and beta 1 subunits that are responsible for cGMP production or NO-heme-mediated activation. The amino terminus of the beta 1 subunit was necessary for NO stimulation since deletion of the 64 NH2-terminal amino acids resulted in a mutant with intact basal activity but complete loss of NO activation. The amino terminus of the alpha 1 subunit also appeared to be essential for NO sensitivity since deletion of 131 NH2-terminal amino acids of alpha 1 led to markedly reduced NO activation. These results suggest that NH2-terminal regions of alpha 1 and beta 1 are involved in NO-heme-mediated signal transduction. The NH2 terminally truncated beta 1 subunit exerted a dominant negative effect exclusively on the NO-stimulated activity of the wild type enzyme, further underlining that the regulatory domain is located within the NH2 terminus of the enzyme. Aside for the structural implications, the mutant represents a powerful tool to investigate nitric oxide-sensitive signaling pathways. Coexpression of the COOH-terminal halves of alpha 1 and beta 1 were sufficient for basal cGMP production while either of the halves expressed alone was inactive. Therefore the COOH-terminal regions appear to contain sufficient information for dimerization and basal enzymatic activity. Thus, we provide the first evidence that the regulatory and catalytic properties of soluble guanylyl cyclase can be attributed to different regions of the subunits and that the catalytic domain can be functionally expressed separately from the NH2-terminal regulatory domain. Taken together with findings on the membrane bound enzyme form, guanylyl cyclases, appear to resemble fusion proteins where different regulatory domains have been joined with a common cGMP-forming segment.

Animals↗
PubMed1994

Mutation of His-105 in the beta 1 subunit yields a nitric oxide-insensitive form of soluble guanylyl cyclase.

Soluble guanylyl cyclase [GTP pyrophosphate-lyase (cyclizing); EC 4.6.1.2] is a hemoprotein that exists as a heterodimer; the heme moiety has been proposed to bind nitric oxide, resulting in a dramatic activation of the enzyme. Mutation of six conserved His residues reduced but did not abolish nitric oxide stimulation whereas a change of His-105 to Phe in the beta 1 subunit yielded a heterodimer that retained basal cyclase activity but failed to respond to nitric oxide. Heme was not detected as a component of the mutant heterodimer and protophorphyrin IX failed to stimulate enzyme activity. The activity of the His mutant was almost identical to that of the wild-type enzyme in the presence of KCN, suggesting that disruption of heme binding is the principal effect of the mutation. Thus, the mutation provides a means to inhibit the nitric oxide-sensitive guanylyl cyclase signaling pathway.

Amino Acid Sequence↗
PubMed1992

Monocytes are responsible for depressed natural killer (NK) activity in both young and elderly low NK responders.

Two age groups--young (19-35) and elderly (70-91)--were compared with respect to natural killer (NK) cytotoxic activity. In both groups, low and high NK responders could be distinguished. Low NK responders constituted about 70% of all elderly and 40% of young individuals. The differences in the magnitude of NK activity among the young and elderly groups could only be observed when peripheral-blood mononuclear cells but not peripheral-blood lymphocytes were used as effector cells in a 51Cr release assay. Experiments with removal or addition of graded numbers of monocytes showed that these cells were responsible for the low level of NK activity in both the young and elderly low NK responders.

Adult↗
PubMed1992

[Activity of NK in elderly people].

Optimally healthy elderly persons, selected according to Senior Protocol criteria, aged 60-93 years were characterized by as high level of NK activity as their young adult, 20-35 years old, counterparts. NK activity of the nearly optimally healthy elderly persons of the corresponding age was significantly lower than that of optimally healthy ones. The lowest values of NK activity were noted for the elderly persons suffering from recurring infections of the respiratory tract.

Aged↗
PubMed1990

An ELISA procedure to detect anti-double-stranded and anti-single-stranded DNA binding antibodies in connective tissue disorders.

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) is described for the measurement of antibodies to native DNA (double-stranded) and to heat-denatured DNA (single-stranded) in sera of patients with connective tissue disorders. DNA bound to polyvinylchloride plates is incubated with serum samples, and antibodies to both single- and double-stranded DNA are detected by means of goat antihuman IgG alkaline phosphatase conjugate. The binding in individual sera is expressed as binding units per milliliter and refers to the absorbance in relation to the absorbance value obtained with a set of standards. The various parameters of the ELISA assay are described, and the results are compared with results of the Crithidia and Farr DNA antibody assays. Two case reports are discussed.

Adult↗