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Köln, Germany

Eichhorst B.,University of Cologne | Cramer P.,CECAD | Hallek M.,University of Cologne
Seminars in Oncology

Only chronic lymphocytic leukemia (CLL) patients with active or symptomatic disease or with advanced Binet or Rai stages require therapy. Prognostic risk factor profile and comorbidity burden are most relevant for the choice of treatment. For physically fit patients, chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab remains the current standard therapy. For unfit patients, treatment with an anti-CD20 antibody (obinutuzumab or rituximab or ofatumumab) plus milder chemotherapy (chlorambucil) may be applied. Patients with a del(17p) or TP53 mutation should be treated with the kinase inhibitors ibrutinib or a combination of idelalisib and rituximab. Clinical trials over the next several years will determine, whether kinase inhibitors, other small molecules, immunotherapeutics, or combinations thereof will further improve outcomes for patients with CLL. © 2016 Elsevier Inc. All rights reserved. Source

Gerl M.J.,University of Heidelberg | Gerl M.J.,Lipotype GmbH | Bittl V.,University of Heidelberg | Kirchner S.,University of Heidelberg | And 11 more authors.

Cell membranes contain hundreds to thousands of individual lipid species that are of structural importance but also specifically interact with proteins. Due to their highly controlled synthesis and role in signaling events sphingolipids are an intensely studied class of lipids. In order to investigate their metabolism and to study proteins interacting with sphingolipids, metabolic labeling based on photoactivatable sphingoid bases is the most straightforward approach. In order to monitor protein-lipid-crosslink products, sphingosine derivatives containing a reporter moiety, such as a radiolabel or a clickable group, are used. In normal cells, degradation of sphingoid bases via action of the checkpoint enzyme sphingosine-1-phosphate lyase occurs at position C2-C3 of the sphingoid base and channels the resulting hexadecenal into the glycerolipid biosynthesis pathway. In case the functionalized sphingosine looses the reporter moiety during its degradation, specificity towards sphingolipid labeling is maintained. In case degradation of a sphingosine derivative does not remove either the photoactivatable or reporter group from the resulting hexadecenal, specificity towards sphingolipid labeling can be achieved by blocking sphingosine-1-phosphate lyase activity and thus preventing sphingosine derivatives to be channeled into the sphingolipid-to-glycerolipid metabolic pathway. Here we report an approach using clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated nuclease Cas9 to create a sphingosine-1-phosphate lyase (SGPL1) HeLa knockout cell line to disrupt the sphingolipidto-glycerolipid metabolic pathway. We found that the lipid and protein compositions as well as sphingolipid metabolism of SGPL1 knock-out HeLa cells only show little adaptations, which validates these cells as model systems to study transient protein-sphingolipid interactions. © 2016 Gerl et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Turpin S.M.,Max Planck Institute for Metabolism Research | Nicholls H.T.,Max Planck Institute for Metabolism Research | Willmes D.M.,Max Planck Institute for Metabolism Research | Mourier A.,CECAD | And 16 more authors.
Cell Metabolism

Ceramides increase during obesity and promote insulin resistance. Ceramides vary in acyl-chain lengths from C14:0 to C30:0 and are synthesized by six ceramide synthase enzymes (CerS1-6). It remains unresolved whether obesity-associated alterations of specific CerSs and their defined acyl-chain length ceramides contribute to the manifestation of metabolic diseases. Here we reveal that CERS6 mRNA expression and C16:0 ceramides are elevated in adipose tissue of obese humans, and increased CERS6 expression correlates with insulin resistance. Conversely, CerS6-deficient (CerS6Δ/Δ) mice exhibit reduced C16:0 ceramides and are protected from high-fat-diet-induced obesity and glucose intolerance. CerS6 deletion increases energy expenditure and improves glucose tolerance, not only in CerS6Δ/Δ mice, but also in brown adipose tissue- (CerS6ΔBAT) and liver-specific (CerS6ΔLIVER) CerS6 knockout mice. CerS6 deficiency increases lipid utilization in BAT and liver. These experiments highlight CerS6 inhibition as a specific approach for the treatment of obesity and type 2 diabetes mellitus, circumventing the side effects of global ceramide synthesis inhibition. © 2014 Elsevier Inc. Source

Kondadi A.K.,University of Cologne | Wang S.,University of Cologne | Montagner S.,University of Cologne | Kladt N.,CECAD | And 8 more authors.
EMBO Journal

The m-AAA protease subunit AFG3L2 is involved in degradation and processing of substrates in the inner mitochondrial membrane. Mutations in AFG3L2 are associated with spinocerebellar ataxia SCA28 in humans and impair axonal development and neuronal survival in mice. The loss of AFG3L2 causes fragmentation of the mitochondrial network. However, the pathogenic mechanism of neurodegeneration in the absence of AFG3L2 is still unclear. Here, we show that depletion of AFG3L2 leads to a specific defect of anterograde transport of mitochondria in murine cortical neurons. We observe similar transport deficiencies upon loss of AFG3L2 in OMA1-deficient neurons, indicating that they are not caused by OMA1-mediated degradation of the dynamin-like GTPase OPA1 and inhibition of mitochondrial fusion. Treatment of neurons with antioxidants, such as N-acetylcysteine or vitamin E, or decreasing tau levels in axons restored mitochondrial transport in AFG3L2-depleted neurons. Consistently, tau hyperphosphorylation and activation of ERK kinases are detected in mouse neurons postnatally deleted for Afg3l2. We propose that reactive oxygen species signaling leads to cytoskeletal modifications that impair mitochondrial transport in neurons lacking AFG3L2. Synopsis Lack of the m-AAA protease subunit AFG3L2 impairs anterograde axonal transport of mitochondria via a mechanism that involves ROS signaling and hyperphosphorylation of the microtubule- associated protein tau. Depletion of AFG3L2 in cortical neurons leads to a specific defect of anterograde axonal transport of mitochondria. The mitochondrial transport defect is independent from OMA1-dependent OPA1 processing. Anterograde axonal transport of mitochondria in AFG3L2-depleted neurons is rescued by reducing tau levels and by treatment with antioxidants. Deletion of Afg3l2 in cortical neurons activates ERK kinases and leads to tau hyperphosphorylation. Impaired axonal transport of mitochondria in the absence of AFG3L2 may explain how its mutation in spinocerebellar ataxia impair neuronal development and survival, and suggests possible therapeutic strategies based on counteracting ROS signaling. © 2014 The Authors. Source

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