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C Renner

Publications and source records attributed to C Renner.

At least 37 records · Page 2Linked to original sources
PubMed2001

Chromosomal localization and promoter analysis of the adenomatous polyposis coli binding protein RP1.

The EB1/RP1 family is a new protein family that is characterized by the ability of its members to serve as interacting partners for the adenomatous polyposis coli (APC) tumour suppressor protein and tubulin. Data obtained with highly conserved yeast homologues suggest that the EB1/RP1 protein family promotes cytoplasmic microtubule dynamics and contributes to the sensor mechanism controlling the cytokinesis checkpoint during mitosis. However, the precise function of this protein family in mammalian cells has not been elucidated so far and remains unclear. Here, we report on the genomic localization of the RP1 gene and the characterization of the corresponding promoter. The RP1 gene was found to be encoded on chromosome 18q21, a locus which is altered or deleted in up to 50% of all patients with colorectal cancer. Promoter analysis revealed that the RP1 gene is under the control of a strong promoter that was 10 times more active in mammalian cells when compared to SV40 promoter. Members of the cyclic AMP response element binding protein family (CREB1 and CREB2) could be identified as transcription factors binding specifically within the RP1 promoter sequence.

Base Sequence↗
PubMed2001

Photoresponsive dendritic azobenzene peptides.

Two dendritic peptides containing a branched lysine core and up to eight azobenzene moieties in the periphery were synthesized on solid support employing the omega-amino acid 4-(aminomethyl)phenylazobenzoic acid. With an additional peptidic tail consisting of an oligolysine portion, water solubility was achieved for the dendrimers, which allowed for the characterization of the cis/trans photoisomerization of the dendritic azobenzene species in both organic and aqueous media. Despite the interactions between the chromophores, which occur particularly in aqueous media, at higher dilution the photoisomerization process was found to proceed to extents that should permit photomodulation of molecular recognition processes between ligands grafted to the photosensitive azobenzene units and receptor molecules.

Azo Compounds↗
PubMed2001

Scanning tunneling spectroscopy of Bi(2)Sr(2)CuO(6+delta): new evidence for the common origin of the pseudogap and superconductivity.

Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi(2)Sr(2)CuO(6+delta) between 275 mK and 82 K. Below T(c) = 10 K, the spectra show a gap with well-defined coherence peaks at +/-Delta(p) approximately 12 meV, which disappear at T(c). Above T(c), the spectra display a clear pseudogap of the same magnitude, gradually filling up and vanishing at T(*) approximately 68 K. The comparison with Bi(2)Sr(2)CaCu(2)O(8+delta) demonstrates that the pseudogap and the superconducting gap scale with each other, providing strong evidence that they have a common origin.

Journal Article↗
PubMed2001

The extracellular human melanoma inhibitory activity (MIA) protein adopts an SH3 domain-like fold.

Melanoma inhibitory activity (MIA) protein is a clinically valuable marker in patients with malignant melanoma, as enhanced values diagnose metastatic melanoma stages III and IV. Here we show that the recombinant human MIA adopts an SH3 domain-like fold in solution, with two perpendicular, antiparallel, three- and five-stranded beta-sheets. In contrast to known structures with the SH3 domain fold, MIA is a single-domain protein, and contains an additional antiparallel beta-sheet and two disulfide bonds. MIA is also the first extracellular protein found to have the SH3 domain-like fold. Furthermore, we show that MIA interacts with fibronectin and that the peptide ligands identified for MIA exhibit a matching sequence to type III human fibronectin repeats, especially to FN14, which is close to an integrin alpha4beta1 binding site. The present study, therefore, may explain the role of MIA in metastasis in vivo, and supports a model in which the binding of human MIA to type III repeats of fibronectin competes with integrin binding, thus detaching cells from the extracellular matrix.

Amino Acid Sequence↗
PubMed2001

Chalcone derivatives antagonize interactions between the human oncoprotein MDM2 and p53.

The oncoprotein MDM2 inhibits the tumor suppressor protein p53 by binding to the p53 transactivation domain. The p53 gene is inactivated in many human tumors either by mutations or by binding to oncogenic proteins. In some tumors, such as soft tissue sarcomas, overexpression of MDM2 inactivates an otherwise intact p53, disabling the genome integrity checkpoint and allowing cell cycle progression of defective cells. Disruption of the MDM2/p53 interaction leads to increased p53 levels and restored p53 transcriptional activity, indicating restoration of the genome integrity check and therapeutic potential for MDM2/p53 binding antagonists. Here, we show by multidimensional NMR spectroscopy that chalcones (1,3-diphenyl-2-propen-1-ones) are MDM2 inhibitors that bind to a subsite of the p53 binding cleft of human MDM2. Biochemical experiments showed that these compounds can disrupt the MDM2/p53 protein complex, releasing p53 from both the p53/MDM2 and DNA-bound p53/MDM2 complexes. These results thus offer a starting basis for structure-based drug design of cancer therapeutics.

Antineoplastic Agents↗
PubMed2001

Analytical solution to the Lipari-Szabo model based on the reduced spectral density approximation offers a novel protocol for extracting motional parameters.

An analytical solution to the Lipari-Szabo model is derived for isotropic overall tumbling. The parameters of the original Lipari-Szabo model, the order parameter S2 and the effective internal correlation time tau(e), are calculated from two values of the spectral density function. If additionally the spectral density value J(0) is known, the exchange contribution R(ex) term can also be determined. The overall tumbling time tau(c) must be determined in advance, for example, from T1/T2 ratios. The required spectral density values are obtained by reduced spectral density mapping from T1, T2, and NOE measurements. Our computer simulations show that the reduced spectral density mapping is a very good approximation in almost all cases in which the Lipari-Szabo model is applicable. The robustness of the analytical formula to experimental errors is also investigated by extensive computer simulations and is found to be similar to that of the fitting procedures. The derived formulas were applied to the experimental 15N relaxation data of ubiquitin. Our results agree well with the published parameter values of S2 and tau(e), which were obtained from standard fitting procedures. The analytical approach to extract parameters of molecular motions may be more robust than standard analyses and provides a safeguard against spurious fitting results, especially for determining the exchange contribution R(ex).

Algorithms↗
PubMed2001

Targeting properties of an anti-CD16/anti-CD30 bispecific antibody in an in vivo system.

Bispecific antibodies are currently being used in clinical trials in increasing numbers in the areas of breast cancer, prostate cancer, non-Hodgkin's lymphoma and Hodgkin's lymphoma. We have previously performed two clinical trials in patients with Hodgkin's disease with an anti-CD30/anti-CD16 bispecific antibody and demonstrated a 30% response rate in a cohort of patients otherwise resistant to standard therapeutic modalities. However, no surrogate marker could be defined in these trials indicative of optimal antibody dosing/scheduling or predictive for favorable response. In order to evaluate accurately the potential biodistribution properties of bispecific antibody in patients, we have performed a detailed analysis of the binding properties and animal model in vivo characteristics of these constructs. For this purpose, the parental antibodies (anti-CD30 and anti-CD16) and the bispecific antibody (anti-CD30/anti-CD16) were radiolabeled with either 125I or 111In. Antibody integrity and binding properties after labeling were confirmed by Scatchard plot and Lindmo analysis. 111In-labeled antibodies revealed superior targeting properties in a standard SCID mouse tumor model. Both the bivalent parental anti-CD30 monoclonal antibody and the monovalent anti-CD30/anti-CD16 bispecific antibody showed excellent uptake in CD30+ tumors which did not differ significantly between the two (maximum uptake 16.5%+/-4.2% vs. 18.4%+/-3.8% injected dose/gram tissue). The equivalent targeting properties of the bispecific antibody compared with the parental anti-CD30 antibody encourages the further clinical development of this bispecific antibody, and might help to explain the clinical responses seen with this antibody so far in patients suffering from Hodgkin's disease.

Animals↗
PubMed2001

Clinical approaches to vaccination in oncology.

Immunotherapy of cancer is still in the early stages of development although almost a century has passed since initial attempts were made to stimulate the immune system in order to destroy malignant cells. Historically, a variety of specific and non-specific immunostimulatory strategies have been administered with only modest clinical success. However, recent advances in tumour immunology, most notably the identification of new tumour antigens and the better understanding of antigen processing and presentation to avoid or break immune tolerance, have paved the way for the development of a variety of novel and specific vaccine approaches. The most important and widely used are whole-cell vaccines, dendritic-cell-based immunotherapy and peptide vaccines. The first wave of clinical trials has revealed that, in general, such vaccination strategies are safe. However, clear examples of clinical responses, especially in conjunction with vaccine-induced immune responses, are still rare. Most clinical trials are too small to allow for comments on the efficacy, and the cohort of patients studied is too heterogeneous with regard to immune status. Therefore, standardised techniques for the accurate assessment of the individual immune phenotype before and during the trial are needed to allow for the identification of the sub-group of patients who will respond favourably to treatment. The precise definition of immune parameters in these patients will then lead the way for optimised treatment procedures that might even be beneficial for a larger group of cancer patients.

Cancer Vaccines↗
PubMed2001

NMR 15N relaxation of the insulin-like growth factor (IGF)-binding domain of IGF binding protein-5 (IGFBP-5) determined free in solution and in complex with IGF-II.

15N NMR relaxation rates of mini-IGFBP-5, an N-terminal insulin-like growth factor binding domain of the insulin-like growth factor binding protein 5 (IGFBP-5), were analysed at three field strengths using the Lipari-Szabo procedure (see below) and reduced spectral density methods. Isotropic and anisotropic Lipari-Szabo models were analysed and an analytical formula for the overall correlation time for anisotropic molecules is presented. Mini-IGFBP-5 was found to be mainly rigid on fast ps time scales except for 11 unstructured flexible residues at the C-terminus. The insulin-like growth factor binding loop in the apo-protein exhibits small amounts of flexibility on fast time scales (ps to ns) but several loop residues show significant exchange broadening. These loop residues display no exchange broadening in the complex of IGF-II/mini-IGFBP-5. The isotropic overall tumbling time in solution at 31 degrees C of mini-IGFBP-5 complexed to IGF-II is tauc = 18.4 +/- 0.2 ns indicating a strong tendency for aggregation.

Animals↗
PubMed2001

Treatment of renal stones by extracorporeal shockwave lithotripsy: an update.

AIM: Despite the extensive experience with minimal invasive stone therapy, there are still different views on the ideal management of renal stones. MATERIALS AND METHODS: Analysis of the literature includes more than 14,000 patients. We have compared these data with long-term results of two major stone centers in Germany. The results have been compared concerning the anatomical kidney situation, stone size, stone localization and observation time. RESULTS: According to the importance of residual fragments following extracorporeal shock wave lithotripsy (ESWL), we have to distinguish between clinically insignificant residual fragments and clinically significant residual fragments (CIRF). 24 months following ESWL stone passage occurs as a continuous process, and if there are no clinical symptoms, any endoscopic procedure should be considered as overtreatment. According to these results, stone-free rates of patients increase in longer follow-up periods. Newer ESWL technology has increased the percentage of CIRF. CONCLUSION: We consider ESWL in most patients with renal calculi as first-line treatment, except in patients with renal calculi bigger than 30 mm in diameter.

Humans↗
PubMed2001

Biodistribution properties of (111)indium-labeled C-functionalized trans-cyclohexyl diethylenetriaminepentaacetic acid humanized 3S193 diabody and F(ab')(2) constructs in a breast carcinoma xenograft model.

The humanized complementarity determining region-grafted anti-Lewis Y (Le(y)) monoclonal antibody [humanized 3S193 (hu3S193)] was developed for targeting Le(y)-expressing epithelial tumors such as breast, colon, lung, prostate, and ovarian carcinoma. We are exploring the potential use of smaller molecular size, bivalent analogues of hu3S193, because the faster blood clearance of M(r) approximately 54,000 diabody and M(r) approximately 110,000 F(ab')(2) molecules may be advantageous in achieving optimal and rapid tumor uptake for diagnostic and potential therapeutic applications. The single-chain variable fragment-5 residue linker construct (diabody) was expressed using the bacterial secretion vector pPOW3, and soluble product was purified without refolding processes. The F(ab')(2) fragment was obtained by pepsin digest of parental hu3S193. To facilitate evaluations, the radiometal (111)In was used to label C-functionalized trans-cyclohexyl diethylenetriaminepentaacetic acid chelated diabody and F(ab')(2). The immunoreactivity of the radiolabeled constructs was 41.3 and 58.6%, and the K(a) was 1.68 x 10(6) M(-1) and 5.33 x 10(6) M(-1) for the diabody and F(ab')(2), respectively. Radioconjugates were injected into mice bearing Le(y)-positive MCF-7 tumors, and biodistribution properties were determined at various time points after injection. The uptake of radiolabeled diabody in xenografts was maximal at 1 h after injection (4.7 +/- 0.6% injected dose/g), whereas the F(ab')(2) peaked at 8 h after injection (14.2 +/- 2.4% injected dose/g). The tumor:blood ratio at 4 h for the diabody and F(ab')(2) was 5:1 and 2:1, which increased to 20:1 and 5:1, respectively, at 8 h and increased further to 40:1 and 130:1, respectively, at 48 h. These results demonstrate that the diabody construct may have applications as a diagnostic imaging reagent, whereas F(ab')(2) displayed effective tumor targeting and may have potential as a therapeutic molecule in patients with Le(y)-expressing tumors.

Animals↗
PubMed2001

Anti-CD16/CD30 bispecific antibody treatment for Hodgkin's disease: role of infusion schedule and costimulation with cytokines.

The natural killer cell-activating anti-CD16/CD30 bispecific monoclonal antibody (BiMAb) had shown efficacy in a Phase I/II trial of refractory Hodgkin's disease (HD). To gain additional information on clinical efficacy and to investigate the effects of different application schedules and the concomitant application of cytokines, we performed a second randomized pilot trial using this BiMAb in patients with refractory HD. Patients received 4 x 25 mg HRS-3/A9 either as a continuous infusion for 4 days or as a 1-h infusion every other day. In case of an objective response, retreatment was attempted after 4 weeks; in case of stable disease (SD), a second course was given after prestimulation with interleukin 2 and followed by granulocyte macrophage colony-stimulating factor s.c. A total of 16 heavily pretreated patients received one to four BiMAb courses. Overall, we observed one complete remission and three partial remissions lasting 5-9 months (three of four of these responses occurred after continuous BiMAb infusion) and four cases of SD for 3 to >6 months. Interleukin 2 pretreatment before the second BiMAb course resulted in a significant increase of circulating natural killer cells in all five patients treated. This coincided with the conversion of two cases of SD into one complete remission and one partial remission. HRS-3/A9-related side effects consisted of mild fever in only six patients. In summary, this second trial confirmed the antitumor efficacy of this BiMAb against HD and the minor toxicity of this BiMAb. Coadministration of cytokines might contribute to an augmented antitumor activity, and additional clinical trials are warranted to optimize this novel treatment modality.

Adult↗
PubMed2000

How to quantify deterministic and random influences on the statistics of the foreign exchange market

It is shown that price changes of the U.S. dollar-German mark exchange rates upon different delay times can be regarded as a stochastic Marcovian process. Furthermore, we show how Kramers-Moyal coefficients can be estimated from the empirical data. Finally, we present an explicit Fokker-Planck equation which models very precisely the empirical probability distributions, in particular, their non-Gaussian heavy tails.

Journal Article↗
PubMed2000

Solution structure of PCP, a prototype for the peptidyl carrier domains of modular peptide synthetases.

BACKGROUND: Nonribosomal peptide synthetases (NRPSs) are large modular enzymes responsible for the synthesis of a variety of microbial bioactive peptides. They consist of modules that each recognise and incorporate one specific amino acid into the peptide product. A module comprises several domains, which carry out the individual reaction steps. After activation by the adenylation domain, the amino acid substrate is covalently tethered to a 4'-phosphopantetheinyl cofactor of a peptidyl carrier domain (PCP) that passes the substrate to the reaction centres of the consecutive domains. RESULTS: The solution structure of PCP, a distinct peptidyl carrier protein derived from the equivalent domain of an NRPS, was solved using NMR techniques. PCP is a distorted four-helix bundle with an extended loop between the first two helices. Its overall fold resembles the topology of acyl carrier proteins (ACPs) from Escherichia coli fatty acid synthase and actinorhodin polyketide synthase from Streptomyces coelicolor; however, the surface polarity and the length and relative alignment of the helices are different. The conserved serine, which is the cofactor-binding site, has the same location as in the ACPs and is situated within a stretch of seven flexible residues. CONCLUSIONS: The structure of PCP reflects its character as a protein domain. The fold is well defined between residues 8 and 82 and the structural core of the PCP domain can now be defined as a region spanning 37 amino acids in both directions from the conserved serine. The flexibility of the post-translationally modified site might have implications for interactions with the cooperating proteins or NRPS domains.

Amino Acid Sequence↗
PubMed2000

Photomodulation of conformational states. I. Mono- and bicyclic peptides with (4-amino)phenylazobenzoic acid as backbone constituent.

The thioredoxin reductase active-site fragment H-Ala-Cys-Ala-Thr-Cys-Asp-Gly-Phe-OH [134-141], which is known for its high tendency to assume an almost identical conformation as in the intact enzyme, was backbone cyclized with the photoresponsive (4-amino)phenylazobenzoic acid (APB) to produce a monocyclic and disulfide-bridged bicyclic APB-peptide. Light-induced reversible cis/trans isomerization occurs at identical extents in both the linear and the two cyclic forms. Nuclear magnetic resonance conformational analysis clearly revealed that in the bicyclic APB-peptide both as a trans- and cis-azo-isomer the constraints imparted by the bicyclic structure do not allow the molecule to relax into a defined low energy conformation, thus making the molecule a frustrated system that flip-flops between multiple conformational states. Conversely, the monocyclic APB peptide folds into a well-defined lowest energy structure as a trans-azo-isomer, which upon photoisomerization to the cis-azo configuration relaxes into a less restricted conformational space. First femtosecond spectroscopic analysis of the dynamics of the photoreaction confirm a fast first phase on the femtosecond time scale related to the cis/trans isomerization of the azobenzene moiety followed by a slower phase in the picosecond time scale that involves an adjustment of the peptide backbone. Due to the well- defined photoresponsive two-state transition of this monocyclic peptide molecule, it represents a model system well suited for studying the ultrafast dynamics of conformational transitions by time-resolved spectroscopy.

Aminobenzoates↗
PubMed2000

Photomodulation of conformational states. II. Mono- and bicyclic peptides with (4-aminomethyl)phenylazobenzoic acid as backbone constituent.

It has been reported that backbone cyclization of octapeptides with the photoresponsive (4-aminomethyl)phenylazobenzoic acid imparts sufficient restraints to induce and stabilize ordered conformations of the peptide backbone in both the cis- and trans-azo-isomers (L. Ulysse, J. Cubillos, and J. Chmielewski, Journal of the American Chemical Society, 1995, Vol. 117, pp. 8466-8467). Correspondingly, the active-site octapeptide fragment H-Ala-Cys-Ala-Thr-Cys-Asp-Gly-Phe-OH [134-141] of thioredoxin reductase, with its high preference for a 3(10)-helix turn conformation centered on the Thr-Cys sequence, was backbone cyclized with this azobenzene moiety in the attempt to design a photoresponsive system where the conformational states of the peptide backbone are dictated by the configuration of the azobenzene and can be further modulated by the disulfide bridge. Nuclear magnetic resonance conformational analysis of the monocyclic compound clearly revealed the presence of two conformational families in both the cis- and trans-azo configuration. Of the higher populated conformational families, the structure of the trans-isomer seems like a pretzel-like folding, while the cis-isomer relaxes into a significantly less defined conformational state that does not exhibit any regular structural elements. Further restrictions imparted by disulfide bridging of the peptide moiety leads to an even better defined conformation for the trans-azo-isomer, whereas the cis-isomer can be described as a frustrated system without pronounced energy minima and thus with little conformational preferences. Our findings would suggest that this photoresponsive peptide template may not be of general usefulness for light-induced conformational transitions between two well-defined conformational states at least under the experimental conditions employed, even in the bicyclic form. However, trans --> cis isomerization of the bicyclic peptide is accompanied by a switch from a well-defined conformation to an ensemble of possible conformations.

Aminobenzoates↗
PubMed2000

Separation of anisotropy and exchange broadening using (15)N CSA-(15)N-(1)H dipole-dipole relaxation cross-correlation experiments.

Based on the measurement of cross-correlation rates between (15)N CSA and (15)N-(1)H dipole-dipole relaxation we propose a procedure for separating exchange contributions to transverse relaxation rates (R(2) = 1/T(2)) from effects caused by anisotropic rotational diffusion of the protein molecule. This approach determines the influence of anisotropy and chemical exchange processes independently and therefore circumvents difficulties associated with the currently standard use of T(1)/T(2) ratios to determine the rotational diffusion tensor. We find from computer simulations that, in the presence of even small amounts of internal flexibility, fitting T(1)/T(2) ratios tends to underestimate the anisotropy of overall tumbling. An additional problem exists when the N-H bond vector directions are not distributed homogeneously over the surface of a unit sphere, such as in helix bundles or beta-sheets. Such a case was found in segment 4 of the gelation factor (ABP 120), an F-actin cross-linking protein, in which the diffusion tensor cannot be calculated from T(1)/T(2) ratios. The (15)N CSA tensor of the residues for this beta-sheet protein was found to vary even within secondary structure elements. The use of a common value for the whole protein molecule therefore might be an oversimplification. Using our approach it is immediately apparent that no exchange broadening exists for segment 4 although strongly reduced T(2) relaxation times for several residues could be mistaken as indications for exchange processes.

Actins↗