Filter and export

Publications

What is a Publication?
47 Publications visible to you, out of a total of 55
Pyruvate kinase: Function, regulation and role in cancer.

Abstract (Expand)

Pyruvate kinase is an enzyme that catalyzes the conversion of phosphoenolpyruvate and ADP to pyruvate and ATP in glycolysis and plays a role in regulating cell metabolism. There are four mammalian … pyruvate kinase isoforms with unique tissue expression patterns and regulatory properties. The M2 isoform of pyruvate kinase (PKM2) supports anabolic metabolism and is expressed both in cancer and normal tissue. The enzymatic activity of PKM2 is allosterically regulated by both intracellular signaling pathways and metabolites; PKM2 thus integrates signaling and metabolic inputs to modulate glucose metabolism according to the needs of the cell. Recent advances have increased our understanding of metabolic regulation by pyruvate kinase, raised new questions, and suggested the possibility of non-canonical PKM2 functions to regulate gene expression and cell cycle progression via protein-protein interactions and protein kinase activity. Here we review the structure, function, and regulation of pyruvate kinase and discuss how these properties enable regulation of PKM2 for cell proliferation and tumor growth.

Authors: W. J. Israelsen, M. G. Vander Heiden

Date Published: 17th Aug 2015

Publication Type: Journal

Genome reduction boosts heterologous gene expression in Pseudomonas putida.

Abstract (Expand)

BACKGROUND: The implementation of novel platform organisms to be used as microbial cell factories in industrial applications is currently the subject of intense research. Ongoing efforts include the … adoption of Pseudomonas putida KT2440 variants with a reduced genome as the functional chassis for biotechnological purposes. In these strains, dispensable functions removed include flagellar motility (1.1% of the genome) and a number of open reading frames expected to improve genotypic and phenotypic stability of the cells upon deletion (3.2% of the genome). RESULTS: In this study, two previously constructed multiple-deletion P. putida strains were systematically evaluated as microbial cell factories for heterologous protein production and compared to the parental bacterium (strain KT2440) with regards to several industrially-relevant physiological traits. Energetic parameters were quantified at different controlled growth rates in continuous cultivations and both strains had a higher adenosine triphosphate content, increased adenylate energy charges, and diminished maintenance demands than the wild-type strain. Under all the conditions tested the mutants also grew faster, had enhanced biomass yields and showed higher viability, and displayed increased plasmid stability than the parental strain. In addition to small-scale shaken-flask cultivations, the performance of the genome-streamlined strains was evaluated in larger scale bioreactor batch cultivations taking a step towards industrial growth conditions. When the production of the green fluorescent protein (used as a model heterologous protein) was assessed in these cultures, the mutants reached a recombinant protein yield with respect to biomass up to 40% higher than that of P. putida KT2440. CONCLUSIONS: The two streamlined-genome derivatives of P. putida KT2440 outcompeted the parental strain in every industrially-relevant trait assessed, particularly under the working conditions of a bioreactor. Our results demonstrate that these genome-streamlined bacteria are not only robust microbial cell factories on their own, but also a promising foundation for further biotechnological applications.

Authors: S. Lieder, P. I. Nikel, V. de Lorenzo, R. Takors

Date Published: 19th Apr 2015

Publication Type: Not specified

Competing G protein-coupled receptor kinases balance G protein and beta-arrestin signaling.

Abstract (Expand)

Seven-transmembrane receptors (7TMRs) are involved in nearly all aspects of chemical communications and represent major drug targets. 7TMRs transmit their signals not only via heterotrimeric G proteins … but also through beta-arrestins, whose recruitment to the activated receptor is regulated by G protein-coupled receptor kinases (GRKs). In this paper, we combined experimental approaches with computational modeling to decipher the molecular mechanisms as well as the hidden dynamics governing extracellular signal-regulated kinase (ERK) activation by the angiotensin II type 1A receptor (AT(1A)R) in human embryonic kidney (HEK)293 cells. We built an abstracted ordinary differential equations (ODE)-based model that captured the available knowledge and experimental data. We inferred the unknown parameters by simultaneously fitting experimental data generated in both control and perturbed conditions. We demonstrate that, in addition to its well-established function in the desensitization of G-protein activation, GRK2 exerts a strong negative effect on beta-arrestin-dependent signaling through its competition with GRK5 and 6 for receptor phosphorylation. Importantly, we experimentally confirmed the validity of this novel GRK2-dependent mechanism in both primary vascular smooth muscle cells naturally expressing the AT(1A)R, and HEK293 cells expressing other 7TMRs.

Authors: D. Heitzler, G. Durand, N. Gallay, A. Rizk, S. Ahn, J. Kim, J. D. Violin, L. Dupuy, C. Gauthier, V. Piketty, P. Crepieux, A. Poupon, F. Clement, F. Fages, R. J. Lefkowitz, E. Reiter

Date Published: 26th Jun 2012

Publication Type: Journal

Functional characterization of GNAS mutations found in patients with pseudohypoparathyroidism type Ic defines a new subgroup of pseudohypoparathyroidism affecting selectively Gsalpha-receptor interaction.

Abstract (Expand)

Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the alpha-subunit of stimulatory G proteins (Gsalpha) that mediate signal transduction of G protein-coupled … receptors via cAMP. PHP type Ic (PHPIc) and PHPIa share clinical features of Albright hereditary osteodystrophy (AHO); however, in vitro activity of solubilized Gsalpha protein is normal in PHPIc but reduced in PHPIa. We screened 32 patients classified as PHPIc for GNAS mutations and identified three mutations (p.E392K, p.E392X, p.L388R) in four unrelated families. These and one novel mutation associated with PHPIa (p.L388P) were introduced into a pcDNA3.1(-) expression vector encoding Gsalpha wild-type and expressed in a Gsalpha-null cell line (Gnas(E2-/E2-) ). To investigate receptor-mediated cAMP accumulation, we stimulated the endogenous expressed beta(2) -adrenergic receptor, or the coexpressed PTH or TSH receptors, and measured the synthesized cAMP by RIA. The results were compared to receptor-independent cholera toxin-induced cAMP accumulation. Each of the mutants associated with PHPIc significantly reduced or completely disrupted receptor-mediated activation, but displayed normal receptor-independent activation. In contrast, PHPIa associated p.L388P disrupted both receptor-mediated activation and receptor-independent activation. We present a new subgroup of PHP that is caused by Gsalpha deficiency and selectively affects receptor coupling functions of Gsalpha.

Authors: S. Thiele, L. de Sanctis, R. Werner, J. Grotzinger, C. Aydin, H. Juppner, M. Bastepe, O. Hiort

Date Published: 14th Apr 2011

Publication Type: Journal

The role of the anterior lateral eyes in the vision-based behaviour of jumping spiders

Abstract (Expand)

SUMMARY Jumping spiders, or salticids, sample their environment using a combination of two types of eyes. The forward-facing pair of ‘principal’ eyes have narrow fields of view, but exceptional spatial …w, but exceptional spatial resolution, while the two or three pairs of ‘secondary’ eyes have wide fields of view and function especially well as motion analysers. Motion detected by the secondary eyes may elicit an orienting response, whereupon the object of interest is examined further using the high-acuity principal eyes. The anterior lateral (AL) eyes are particularly interesting, as they are the only forward-facing pair of secondary eyes. In this study, we aimed to determine characteristics of stimuli that elicit orienting responses mediated by the AL eyes. After covering all eyes except the AL eyes, we measured orienting responses to dot stimuli that varied in size and contrast, and moved at different speeds. We found that all stimulus parameters had significant effects on orientation propensity. When tethered flies were used as prey, we found that visual information from the AL eyes alone was sufficient to elicit stalking behaviour. These results suggest that, in terms of overall visual processing, the relevance of spatial vision in the AL eyes has been underestimated in the literature. Our results also show that female spiders are significantly more responsive than males. We found that hunger caused similar increases in orientation propensity in the two sexes, but females responded more often than males both when sated and when hungry. A higher propensity by females to orient toward moving objects may be related to females tending to experience higher nutritional demands than males.

Authors: Daniel B. Zurek, Alan J. Taylor, Christopher S. Evans, Ximena J. Nelson

Date Published: 15th Jul 2010

Publication Type: Journal

A star-PEG-heparin hydrogel platform to aid cell replacement therapies for neurodegenerative diseases.

Abstract (Expand)

Biofunctional matrices for in vivo tissue engineering strategies must be modifiable in both biomolecular composition and mechanical characteristics. To address this challenge, we present a modular … system of biohybrid hydrogels based on covalently cross-linked heparin and star-shaped poly(ethylene glycols) (star-PEG) in which network characteristics can be gradually varied while heparin contents remain constant. Mesh size, swelling and elastic moduli were shown to correlate well with the degree of gel component cross-linking. Additionally, secondary conversion of heparin within the biohybrid gels allowed the covalent attachment of cell adhesion mediating RGD peptides and the non-covalent binding of soluble mitogens such as FGF-2. We applied the biohybrid gels to demonstrate the impact of mechanical and biomolecular cues on primary nerve cells and neural stem cells. The results demonstrate the cell type-specific interplay of synergistic signaling events and the potential of biohybrid materials to selectively stimulate cell fate decisions. These findings suggest important future uses for this material in cell replacement based-therapies for neurodegenerative diseases.

Authors: U. Freudenberg, A. Hermann, P. B. Welzel, K. Stirl, S. C. Schwarz, M. Grimmer, A. Zieris, W. Panyanuwat, S. Zschoche, D. Meinhold, A. Storch, C. Werner

Date Published: 30th Jun 2009

Publication Type: Journal

The Synthesis Rates of Total Liver Protein and Plasma Albumin Determined Simultaneously In Vivo In Humans

Abstract (Expand)

Although the metabolism of liver–derived plasma proteins such as albumin has been extensively studied, human hepatic protein synthesis as a whole has not been well characterized, because a reproducible … a whole has not been well characterized, because a reproducible model for obtaining human liver tissue has not been available. In this study, the fractional synthesis rates of total liver protein and albumin in vivo were determined simultaneously in nine subjects undergoing elective laparoscopic cholecystectomy. l–[2H5]phenylalanine (45 mg/kg body wt) was administered for 10 minutes intravenously. Blood samples were collected at regular intervals for 90 minutes and a liver biopsy specimen was taken at 35 ± 7 minutes. The enrichments of plasma free phenylalanine, plasma albumin, and total liver protein were measured with gas chromatography mass spectrometry (GC–MS). The fractional synthesis rate (FSR) of total liver protein was 24.7 ± 3.1 %/d (mean ± SD), and that of albumin was 5.9 ±1.2%/d. The amount of albumin synthesized per day (absolute synthesis rate, ASR) was 109 ± 21 mg/kg body wt. No correlation between FSR of total liver protein and ASR of albumin was found. It is concluded that the technique of obtaining liver tissue specimens during laparoscopic surgery may serve as a human in vivo model to study total liver protein synthesis. The fractional synthesis rate of total liver proteins (stationary and exported), equals approximately 25% of the liver protein content daily. Within the range of values of this study, the absolute synthesis rate of albumin was not correlated to the fractional synthesis rate of total liver protein.

Authors: H. Barle, B. Nyberg, P. Essén, K. Andersson, M. A. McNurlan, J. Wernerman, P. J. Garlick

Date Published: 1997

Publication Type: Journal

Powered by
 (v.1.16.0-pre)
About FAIRDOM | Funding and Programmes | Credits
Copyright © 2008 - 2024 The University of Manchester and HITS gGmbH