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Jinnah H.A.,Emory University | Sabina R.L.,Oakland University | Van Den Berghe G.,University of Leuven Medical School
Handbook of Clinical Neurology | Year: 2013

The purines are a group of molecules used by all cells for many vital biochemical processes including energy-requiring enzymatic reactions, cofactor-requiring reactions, synthesis of DNA or RNA, signaling pathways within and between cells, and other processes. Defects in some of the enzymes of purine metabolism are known to be associated with specific clinical disorders, and neurological problems may be a presenting sign or the predominant clinical problem for several of them. This chapter describes three disorders for which the clinical features and metabolic basis are well characterized. Deficiency of adenylosuccinate-lyase (ADSL) causes psychomotor retardation, epilepsy, and autistic features. Lesch-Nyhan disease is caused by deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and is characterized by hyperuricemia, motor and cognitive disability, and self-injurious behavior. Deficiency of myoadenylate deaminase (mAMPD) is associated with myopathic features. In addition to these disorders, several other disorders are briefly summarized. These include defects of phosphoribosylpyrophosphate synthase, adenosine deaminase (ADA), purine nucleoside phosphorylase (PND), deoxyguanosine kinase (dGK), or IMP dehydrogenase (IMPDH). Each of these disorders provides an unusual window on the unique importance of purine metabolism for function of different parts of the nervous system. © 2013 Elsevier B.V.

Eschenhagen T.,University of Hamburg | Force T.,Philadelphia University | Ewer M.S.,University of Houston | De Keulenaer G.W.,University of Antwerp | And 26 more authors.
European Journal of Heart Failure | Year: 2011

The reductions in mortality and morbidity being achieved among cancer patients with current therapies represent a major achievement. However, given their mechanisms of action, many anti-cancer agents may have significant potential for cardiovascular side effects, including the induction of heart failure. The magnitude of this problem remains unclear and is not readily apparent from current clinical trials of emerging targeted agents, which generally under-represent older patients and those with significant co-morbidities. The risk of adverse events may also increase when novel agents, which frequently modulate survival pathways, are used in combination with each other or with other conventional cytotoxic chemotherapeutics. The extent to which survival and growth pathways in the tumour cell (which we seek to inhibit) coincide with those in cardiovascular cells (which we seek to preserve) is an open question but one that will become ever more important with the development of new cancer therapies that target intracellular signalling pathways. It remains unclear whether potential cardiovascular problems can be predicted from analyses of such basic signalling mechanisms and what pre-clinical evaluation should be undertaken. The screening of patients, optimization of therapeutic schemes, monitoring of cardiovascular function during treatment, and the management of cardiovascular side effects are likely to become increasingly important in cancer patients. This paper summarizes the deliberations of a cross-disciplinary workshop organized by the Heart Failure Association of the European Society of Cardiology (held in Brussels in May 2009), which brought together clinicians working in cardiology and oncology and those involved in basic, translational, and pharmaceutical science. © 2010 The Author.

Jossin Y.,Fred Hutchinson Cancer Research Center | Jossin Y.,University of Leuven Medical School
Small GTPases | Year: 2011

Neuronal migration is essential for the development of the cerebral cortex. Mutations leading to defective migration are associated with numerous brain pathologies. An important challenge in the field is to understand the intrinsic and extrinsic mechanisms that regulate neuronal migration during normal development and in disease. Many small GTPases are expressed in the central nervous system during embryonic development. Recent findings have shown that Rap1 and its downstream partners Ral, Rac and Cdc42 are involved in themaintenance of N-Cadherin at the plasma membrane which is necessary for the correct polarization of migrating neurons. The activation of Rap1 is triggered by Reelin, an extracellular protein known for its role in the organization of the cortex into layers of neurons. In the absence of Reelin, neurons exhibit a broader and irregular pattern of positioning. The prevailing model suggests that Reelin signals to neurons during the last step of their migration, a notion that is inconsistent with new data describing an effect of Reelin on early steps of migration. In regard to these recent findings I suggest a revised model, which I call the "polarity model," that further refines our understanding of the developmental function played by Reelin and its downstream small GTPases. © 2011 Landes Bioscience.

Maritzen T.,Charite - Medical University of Berlin | Schmidt M.R.,Charite - Medical University of Berlin | Kukhtina V.,Charite - Medical University of Berlin | Higman V.A.,Leibniz Institute for Molecular Pharmacology | And 6 more authors.
Journal of Biological Chemistry | Year: 2010

Membrane traffic between the trans-Golgi network (TGN) and endosomes is mediated in part by the assembly of clathrin-AP-1 adaptor complex-coated vesicles. This process involves multiple accessory proteins that directly bind to the ear domain of AP-1γ via degenerate peptide motifs that conform to the consensus sequence ∅G(P/D/E)(∅/L/M) (with ∅ being a large hydrophobic amino acid). Recently, γ-BAR (hereafter referred to as Gadkin for reasons explained below) has been identified as a novel AP-1 recruitment factor involved in AP-1-dependent endosomal trafficking of lysosomal enzymes. How precisely Gadkin interacts with membranes and with AP-1γ has remained unclear. Here we show that Gadkin is an S-palmitoylated peripheral membrane protein that lacks stable tertiary structure. S-Palmitoylation is required for the recruitment of Gadkin to TGN/endosomal membranes but not for binding to AP-1. Furthermore, we identify a novel subtype of AP-1-binding motif within Gadkin that specifically associates with the γ1-adaptin ear domain. Mutational inactivation of this novel type of motif, either alone or in combination with three more conventional AP-1γ binding peptides, causes Gadkin to mislocalize to the plasma membrane and interferes with its ability to render AP-1 brefeldin A-resistant, indicating its physiological importance. Our studies thus unravel the molecular basis for Gadkin-mediated AP-1 recruitment to TGN/endosomal membranes and identify a novel subtype of the AP-1-binding motif. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

Dadhich R.K.,University of Granada | Dadhich R.K.,University of Leuven Medical School | Barrionuevo F.J.,University of Granada | Real F.M.,University of Granada | And 5 more authors.
Biology of Reproduction | Year: 2013

In males of seasonally breeding species, testes undergo a severe involution at the end of the breeding season, with a major volume decrease due to massive germ-cell depletion associated with photoperiod-dependent reduced levels of testosterone and gonadotropins. Although it has been repeatedly suggested that apoptosis is the principal effector of testicular regression in vertebrates, recent studies do not support this hypothesis in some mammals. The purpose of our work is to discover alternative mechanisms of testis regression in these species. In this paper, we have performed a morphological, hormonal, ultrastructural, molecular, and functional study of the mechanism of testicular regression and the role that cell junctions play in the cell-content dynamics of the testis of the Iberian mole, Talpa occidentalis, throughout the seasonal breeding cycle. Desquamation of live, nonapoptotic germ cells has been identified here as a new mechanism for seasonal testis involution in mammals, indicating that testis regression is regulated by modulating the expression and distribution of the cell-adhesion molecules in the seminiferous epithelium. During this process, which is mediated by low intratesticular testosterone levels, Sertoli cells lose their nursing and supporting function, as well as the impermeability of the blood-testis barrier. Our results contradict the current paradigm that apoptosis is the major testis regression effector in vertebrates, as it is clearly not true in all mammals. The new testis regression mechanism described here for the mole could then be generalized to other mammalian species. Available data from some previously studied mammals should be reevaluated.

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