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Biomedical subjects

K Rother

Publications and source records attributed to K Rother.

At least 19 recordsLinked to original sources
PubMed2006

p53 downregulates expression of the G1/S cell cycle phosphatase Cdc25A.

Overexpression of Cdc25A phosphatase is often observed in cancer and results in poor prognosis. Cdc25A mainly dephosphorylates and thereby activates Cyclin-dependent kinase 2 and thus induces progression in the cell cycle from G(1) to S phase. Here, we demonstrate that the tumor suppressor p53 downregulates expression from the Cdc25A gene. In a p53-inducible cell system, Cdc25A expression on the mRNA and protein level is downregulated upon p53 expression. Promoter-reporter assays show that this regulation is dependent on the Cdc25A promoter. Mutant p53 fails to reduce Cdc25A transcription. In contrast to p53, neither p63 nor p73 can repress Cdc25A transcription. The Cdc25A promoter displays no p53 binding site, and p53 does not bind directly to the promoter DNA as shown by chromatin immunoprecipitation assays. Previously, the contribution of p53 to G(1)/S arrest has been mostly linked to activating the expression of the Cdk inhibitor p21(WAF1/CIP1). By downregulating Cdc25A expression, p53 may impair transition from G(1) to S phase independently of p21(WAF1/CIP1). Therefore, the data suggest that, as long as p53 is intact, Cdc25A transcriptional downregulation might play a role in cancer prevention.

Chromatin Immunoprecipitation↗
PubMed2001

Matching organic libraries with protein-substructures.

We present a general approach which allows automatic identification of sub-structures in proteins that resemble given three-dimensional templates. This paper documents its success with non-peptide templates such as beta-turn mimetics. We considered well-tested turn-mimetics such as the bicyclic turned dipeptide (BTD), spiro lactam (Spiro) and the 2,5-disubstituded tetrahydrofuran (THF), a new furan-derivative which was recently developed and characterized. The detected geometric similarity between the templates and the protein patches corresponds to r.m.s.-values of 0.3 A for more than 80% of the constituting atoms, which is typical for active site comparisons of homologous proteins. This fast automatic procedure might be of biomedical value for finding special mimicking leads for particular protein sub-structures as well as for template-assembled synthetic protein (TASP) design.

Computer Simulation↗
PubMed2000

Conservation of substructures in proteins: interfaces of secondary structural elements in proteasomal subunits.

It is observed that during divergent evolution of two proteins with a common phylogenetic origin, the structural similarity of their backbones is often preserved even when the sequence similarity between them decreases to a virtually undetectable level. Here we analyzed, whether the conservation of structure along evolution involves also the local atomic structures in the interfaces between secondary structural elements. We have used as study case one protein family, the proteasomal subunits, for which 17 crystal structures are known. These include 14 different subunits of Saccharomyces cerevisiae, 2 subunits of Thermoplasma acidophilum and one subunit of Escherichia coli. The structural core of the 17 proteasomal subunits has 23 secondary structural elements. Any two adjacent secondary structural elements form a molecular interface consisting of two molecular patches. We found 61 interfaces that occurred in all 17 subunits. The 3D shape of equivalent molecular patches from different proteasomal subunits were compared by superposition. Our results demonstrate that pairs of equivalent molecular patches show an RMSD which is lower than that of randomly chosen patches from unrelated proteins. This is true even when patch comparisons with identical residues were excluded from the analysis. Furthermore it is known that the sequential dissimilarity is correlated to the RMSD between the backbones of the members of protein families. The question arises whether this is also true for local atomic structures. The results show that the correlation of individual patch RMSD values and local sequence dissimilarities is low and has a wide range from 0 to 0.41, however, it is surprising that there is a good correlation between the average RMSD of all corresponding patches and the global sequence dissimilarity. This average patch RMSD correlates slightly stronger than the C(alpha)-trace RMSD to the global sequence dissimilarity.

Algorithms↗
PubMed1998

Premature translation of oskar in oocytes lacking the RNA-binding protein bicaudal-C.

Bicaudal-C (Bic-C) is required during Drosophila melanogaster oogenesis for several processes, including anterior-posterior patterning. The gene encodes a protein with five copies of the KH domain, a motif found in a number of RNA-binding proteins. Using antibodies raised against the BIC-C protein, we show that multiple isoforms of the protein exist in ovaries and that the protein, like the RNA, accumulates in the developing oocyte early in oogenesis. BIC-C protein expressed in mammalian cells can bind RNA in vitro, and a point mutation in one of the KH domains that causes a strong Bic-C phenotype weakens this binding. In addition, oskar translation commences prior to posterior localization of oskar RNA in Bic-C- oocytes, indicating that Bic-C may regulate oskar translation during oogenesis.

Alleles↗
PubMed1997

The effect of anti-L-selectin (EL-246) on remote lung injury after infrarenal ischemia/reperfusion.

The clinical concern in using neutrophil adhesion blocking agents is whether or not neutrophil function may be down-regulated, rendering neutrophils incapable of dealing with infections that may threaten the patient. In a sheep model of ischemia and reperfusion, we have investigated the effect of anti-L-selectin (EL-246) on the pulmonary injury as well as on the neutrophil function, assessed by in vitro chemiluminescence (CL) of isolated neutrophils. Infrarenal ischemia (3 h) followed by reperfusion (4 h) resulted in pulmonary capillary leakage as evident by an increased alveolar/plasma protein ratio (.76 vs. .19 in control, p < .01) and also led to a significant pulmonary neutrophil accumulation as assessed by the myeloperoxidase content in homogenized lung tissue (31.7 vs. 6.1 U, p < .01). Anti-L-selectin, infused at a dose of 1 mg/kg at the time of reperfusion, significantly reduced the pulmonary leakage by 59% (.42 vs. .76 U) and neutrophil accumulation by 84% (10.2 vs. 31.7 U). Pulmonary function improved by anti-L-selectin as represented by an increase of the arterio-venous oxygen ratio. CL decreased from 1.85 x 10(5) counts(c)/min to 1.02 x 10(6) c/min at 15 min of reperfusion in the positive control followed by a subsequent return to normal. In contrast to myeloperoxidase, the significant change in CL was not affected by the use of anti-L-selectin. Based on our data, we conclude that anti-L-selectin is able to significantly reduce the pulmonary injury in ischemia-reperfusion but in parallel does not result in neutrophil dysfunction regarding for example, the respiratory burst. Thus, using neutrophil adhesion blocking agents in patients appears to be unlikely to increase the risk of septic complications.

Animals↗
PubMed1993

Interleukin-4 augments production of the third complement component by the alveolar epithelial cell line A549.

The elements of allergic inflammation and the involvement of helper T lymphocytes are increasingly being recognized in the immunopathogenesis of asthma. Allergen exposure leading to the activation of allergen-specific T cells present in the lung can result in the release of cytokines which in turn can locally stimulate the cellular constituents of the lung. The airway epithelial cells may be the key participants in such an interaction. Therefore, we examined the ability of T-cell-derived IL-4 to modulate the production of C3 and C5 by the human type-II pneumocyte cell line A549, which is known to produce all the components and the regulatory proteins of the complement system. For estimation of C3 an ELISA detecting native C3 was used. Following stimulation of A549 with hrIL-4 a dose-dependent (1-50 U/ml) enhancement of C3 production was observed, which reached its maximum (5-fold of unstimulated cells) at 48 h and gradually declined thereafter. Concentrations of hrIL-4 higher than 50 U/ml did not further increase C3 production. In parallel experiments hrIFN-gamma at concentrations between 10 and 50 U/ml stimulated the C3 production to more than twice the quiescent state level within 24 h. In the pneumocyte cell line A549 we demonstrated the expression of a gene for the IL-4 receptor which appears to mediate the biological effect of this lymphokine. A diminution in the functionally active C5, estimated by ELISA at the same time, was observed in supernatants of A549 cultures following stimulation with hrIL-4 as well as with hrIFN-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗
PubMed1991

Complement in inflammation: induction of nephritides and progress to chronicity.

The C5b-9 complex has a dual role as a factor involved in the initiation of nephritides and in the progress to chronicity and sclerosis. The unique pathophysiology of the membrane attack complex, distinct from other mediators, is its independence from specific receptors. It inserted in any membrane lipid bilayer tested so far.

Animals↗
PubMed1991

Induction of mediator release from human glomerular mesangial cells by the terminal complement components C5b-9.

Exposure of cultured human glomerular mesangial cells (GMC) to normal human serum and an activator of the complement system results in rapid uptake of the terminal complement proteins C5b-9 by the cells. This 'innocent bystander' complement attack, however, does not result in cell killing, but in the stimulation of the GMC to release prostaglandin E (PGE), interleukin 1 (Il-1) and tumor necrosis factor (TNF). Endogenously synthesized Il-1 in turn activates PGE release, indicating that the C5b-9 attack initiates an autocrine feedback stimulation. Together with the fact that C5b-9 is found in many forms of glomerulonephritis, the data point to a role of the terminal complement proteins in the initiation and perpetuation of an inflammatory response.

Complement Membrane Attack Complex↗
PubMed1990

C5b-8 and C5b-9 modulate the collagen release of human glomerular epithelial cells.

Aside from their lytic function the late complement components C5b-9 stimulate release of prostanoids, interleukin 1 and oxygen radicals from a number of cells. Since C5b-9 has also been connected to the development of sclerosis in animal models of glomerulonephritis, we addressed the question whether C5b-9 would affect the collagen synthesis. We used human glomerular epithelial cells (GEC) obtained as primary outgrowth cultures. The cells were cultivated in the presence of 14C-proline. Collagen synthesis was quantitated by counting the radioactivity associated with collagenase digestible material. Furthermore, collagen was analyzed by SDS-PAGE. GEC in culture produce spontaneously some collagen type IV. Addition of sublytic doses of highly purified C5b-9 increased the collagen synthesis considerably within 12 to 24 hours. In the absence of C9, C5b-8 stimulated collagen synthesis to a similar extent, whereas in the absence of C7 or C8, the collagen synthesis was not enhanced. Furthermore, fluid-phase-formed C5b-9 complexes did not stimulate the collagen synthesis, indicating that assembly of the complex on the target membrane was required. Since C5b-9 deposits are found in sclerotic areas, our data support the hypothesis that C5b-9, by stimulating collagen synthesis as well as release, might contribute to the development of chronic nephritis.

Animals↗
PubMed1989

Effect of recombinant human growth hormone on urinary 15N-nitrogen balance in girls with Turner syndrome as compared to children with growth hormone deficiency.

15N-nitrogen balances before and on human growth hormone (hGH) were studied in 13 girls with Turner syndrome (TS) aged 4.4-16 (median 13.2) years (45,X0 or equivalent, no X0/XX mosaicism, no estrogen replacement). The results were compared with those reported from 9 patients with growth hormone deficiency (GHD). The TS patients received subcutaneous hGH doses of 2 x 3 (group A, n = 6), 3 x 2 (group B, n = 3), or 2 x 6 (group C, n = 4) IU/m2 on consecutive days. The mean 15N dose given to the patients of groups A and C was higher (13.6 mg/kg) than that given to those of group B (2.7 mg/kg). The lower hGH doses in the first two groups induced small positive mean 15N balance changes (+0.6 +/- 0.6 mg/kg 15N, group A; +0.03 mg/kg, group B). The higher hGH dose in group C caused a more marked mean balance change (+3.0 mg/kg 15N) comparable to that in GHD patients (+3.2 mg/kg). Individual variation of response, however, was larger in patients with TS than in those with GHD. With low and high hGH doses, there were responders and nonresponders. It is concluded from this pilot study in a small number of cases that 15N balance studies might be potentially useful to choose the appropriate hGH dose for long-term treatment in TS patients.

Adolescent↗
PubMed1989

Modulation of collagen synthesis in human glomerular epithelial cells by interleukin 1.

Human glomerular epithelial cells produce matrix material e.g. collagen type IV. In vitro, the synthesis of collagen can be monitored by the incorporation of 3H-proline, a precursor molecule of the collagens. We report on the enhancement of collagen synthesis by glomerular epithelial cells with highly purified or recombinant I1-1. Since I1-1 is released from monocytes or glomerular mesangial cells by inflammatory mediators, our results point to a participation of I1-1 in the development of sclerosis, which is seen in many forms of chronic inflammatory diseases.

Cells, Cultured↗