338 research outputs found
Glycogen pathways in disease: new developments in a classical field of medical genetics
No full textGlycogen is the storage form of glucose in animal cells. Its degradation can rapidly provide fuel for energy production (particularly important in muscle), or replenish blood glucose during fasting by the liver. Genetic defects of glycogen metabolism give rise to glycogen storage diseases (GSDs), manifesting histologically in abnormal quantity or quality of glycogen in the cells. GSDs can be caused by defects of proteins participating in the synthesis or degradation of glycogen itself, in the glycolytic degradation of glucose phosphates in muscle and erythrocytes, in the release of glucose from liver and kidney into the bloodstream, in the clearance of glycogen from lysosomes (all, "primary GSDs"), or in the control of these pathways ("secondary GSDs"). Most genes responsible for classical, primary GSDs have probably been identified, and future progress in understanding the biochemical and genetic defects underlying unsolved disorders presenting with glycogen storage abnormalities will perhaps be predominantly in the field of secondary GSDs
Neurobeachin, a protein implicated in membrane protein traffic and autism, is required for the formation and functioning of central synapses
No full textThe development of neuronal networks in the brain requires the differentiation of functional synapses. Neurobeachin (Nbea) was identified as a putative regulator of membrane protein trafficking associated with tubulovesicular endomembranes and postsynaptic plasma membranes. Nbea is essential for evoked transmission at neuromuscular junctions, but its role in the central nervous system has not been characterized. Here, we have studied central synapses of a newly generated gene-trap knockout (KO) mouse line at embryonic day 18, because null-mutant mice are paralysed and die perinatally. Although the overall brain architecture was normal, we identified major abnormalities of synaptic function in mutant animals. In acute slices from the brainstem, both spontaneous excitatory and inhibitory postsynaptic currents were clearly reduced and failure rates of evoked inhibitory responses were markedly increased. In addition, the frequency of miniature excitatory and both the frequency and amplitudes of miniature inhibitory postsynaptic currents were severely diminished in KO mice, indicating a perturbation of both action potential-dependent and -independent transmitter release. Moreover, Nbea appears to be important for the formation and composition of central synapses because the area density of mature asymmetric contacts in the fetal brainstem was reduced to 30% of wild-type levels, and the expression levels of a subset of synaptic marker proteins were smaller than in littermate controls. Our data demonstrate for the first time a function of Nbea at central synapses that may be based on its presumed role in targeting membrane proteins to synaptic contacts, and are consistent with the 'excitatory-inhibitory imbalance' model of autism where Nbea gene rearrangements have been detected in some patients
Severe neurodegeneration with impaired autophagy mechanism triggered by Ostm1 deficiency
No full textBackground: Although loss of the Ostm1 gene leads to the most severe form of osteopetrosis, Ostm1 is expressed in other tissues, including the CNS. Results: Independently of hematopoietic lineages, loss of Ostm1 results in acute neurodegeneration with enhanced autophagy. Conclusion: We present evidence for an Ostm1 cell-autonomous role in neurons. Significance: This study shows a novel molecular pathogenic mechanism for neurodegeneration-related diseases. Loss of Ostm1 leads to the most severe form of osteopetrosis in mice and humans. Because functional rescue of the osteopetrotic defect in these mice extended their lifespan from approximate to 3 weeks to 6 weeks, this unraveled a second essential role of Ostm1. We discovered that Ostm1 is highly expressed in the mouse brain in neurons, microglia, and astrocytes. At 3-4 weeks of age, mice with Ostm1 loss showed 3-10-fold stimulation of reactive gliosis, with an increased astrocyte cell population and microglia activation. This inflammatory response was associated with marked retinal photoreceptor degeneration and massive neuronal loss in the brain. Intracellular characterization of neurons revealed abnormal storage of carbohydrates, lipids, and ubiquitinated proteins, combined with marked accumulation of autophagosomes that causes frequent axonal swelling. Stimulation of autophagy was provided by specific markers and by significant down-regulation of the mammalian target of rapamycin signaling, identifying a cellular pathologic mechanism. A series of transgenic mouse lines specifically targeted to distinct central nervous system cell subpopulations determined that Ostm1 has a primary and autonomous role in neuronal homeostasis. Complete functional complementation demonstrated that the development of severe and rapid neurodegeneration in these mice is independent of the hematopoietic lineage and has clinical implications for treatment of osteopetrosis. Importantly, this study establishes a novel neurodegenerative mouse model critical for understanding the multistep pathogenic cascade of cellular autophagy disorders toward therapeutic strategy design.Canadian Institutes of Health Research [86655
Paralemmin-1 is expressed in lymphatic endothelial cells and modulates cell migration, cell maturation and tumor lymphangiogenesis
No full textThe lymphatic system, the network of lymphatic vessels and lymphoid organs, maintains the body fluid balance and ensures the immunological surveillance of the body. In the adult organism, the de novo formation of lymphatic vessels is mainly observed in pathological conditions. In contrast to the molecular mechanisms governing the generation of the lymphatic vasculature during embryogenesis, the processes underlying pathological lymphangiogenesis are less well understood. A genome-wide screen comparing the transcriptome of tumor-derived lymphatic endothelial cells with that of blood vessel endothelial cells identified paralemmin-1 as a protein prominently expressed in lymphatic endothelial cells. Paralemmin-1 is a lipid-anchored membrane protein that in fibroblasts and neurons plays a role in the regulation of cell shape, plasma membrane dynamics and cell motility. Here, we show that paralemmin-1 is expressed in tumor-derived lymphatic endothelial cells as well as in lymphatic endothelial cells of normal, non-tumorigenic tissue. Paralemmin-1 represses cell migration and delays the formation of tube-like structures of lymphatic endothelial cells in vitro by modulating cell-substrate adhesion, filopodia formation and plasma membrane blebbing. While constitutive genetic ablation of paralemmin-1 expression in mice has no effect on the development and physiological function of the lymphatic system, the loss of paralemmin-1 impaired tumor-associated lymphangiogenesis. Together, these results newly identify paralemmin-1 as a protein highly expressed in lymphatic endothelial cells. Similar to its function in neurons, it may link the cytoskeleton to the plasma membrane and thereby modulate lymphatic endothelial cell adhesion, migration and lymphangiogenesis
LRBA, a BEACH protein mutated in human immune deficiency, is widely expressed in epithelia, exocrine and endocrine glands, and neurons
No full textMutations in LRBA, a BEACH domain protein, cause severe immune deficiency in humans. LRBA is expressed in many tissues and organs according to biochemical analysis, but little is known about its cellular and subcellular localization, and its deficiency phenotype outside the immune system. By LacZ histochemistry of Lrba gene-trap mice, we performed a comprehensive survey of LRBA expression in numerous tissues, detecting it in many if not all epithelia, in exocrine and endocrine cells, and in subpopulations of neurons. Immunofluorescence microscopy of the exocrine and endocrine pancreas, salivary glands, and intestinal segments, confirmed these patterns of cellular expression and provided information on the subcellular localizations of the LRBA protein. Immuno-electron microscopy demonstrated that in neurons and endocrine cells, which co-express LRBA and its closest relative, neurobeachin, both proteins display partial association with endomembranes in complementary, rather than overlapping, subcellular distributions. Prominent manifestations of human LRBA deficiency, such as inflammatory bowel disease or endocrinopathies, are believed to be primarily due to immune dysregulation. However, as essentially all affected tissues also express LRBA, it is possible that LRBA deficiency enhances their vulnerability and contributes to the pathogenesis
Neurobeachin regulates neurotransmitter receptor trafficking to synapses
No full textThe surface density of neurotransmitter receptors at synapses is a key determinant of synaptic efficacy. Synaptic receptor accumulation is regulated by the transport, postsynaptic anchoring, and turnover of receptors, involving multiple trafficking, sorting, motor, and scaffold proteins. We found that neurons lacking the BEACH (beige-Chediak/Higashi) domain protein Neurobeachin (Nbea) had strongly reduced synaptic responses caused by a reduction in surface levels of glutamate and GAB
Lipopolysaccharide-responsive beige-like anchor is involved in regulating NF-κB activation in B cells
No full textIntroductionLipopolysaccharide-responsive and beige-like anchor (LRBA) is a scaffolding protein that interacts with proteins such as CTLA-4 and PKA, the importance of which has been determined in various cell types, including T regulatory cells, B cells, and renal cells. LRBA deficiency is associated with an inborn error in immunity characterized by immunodeficiency and autoimmunity. In addition to defects in T regulatory cells, patients with LRBA deficiency also exhibit B cell defects, such as reduced cell number, low memory B cells, hypogammaglobulinemia, impaired B cell proliferation, and increased autophagy. Although Lrba-/- mice do not exhibit the immunodeficiency observed in humans, responses to B cell receptors (BCR) in B cells have not been explored. Therefore, a murine model is for elucidating the mechanism of Lrba mechanism in B cells.AimTo compare and evaluate spleen-derived B cell responses to BCR crosslinking in C57BL6 Lrba-/- and Lrba+/+ mice.Materials and methodsSpleen-derived B cells were obtained from 8 to 12-week-old mice. Subpopulations were determined by immunostaining and flow cytometry. BCR crosslinking was assessed by the F(ab’)2 anti-μ chain. Activation, proliferation and viability assays were performed using flow cytometry and protein phosphorylation was evaluated by immunoblotting. The nuclear localization of p65 was determined using confocal microscopy. Nur77 expression was evaluated by Western blot.ResultsLrba-/- B cells showed an activated phenotype and a decreased proportion of transitional 1 B cells, and both proliferation and survival were affected after BCR crosslinking in the Lrba-/- mice. The NF-κB pathway exhibited a basal activation status of several components, resulting in increased activation of p50, p65, and IκBα, basal p50 activation was reduced by the Plcγ2 inhibitor U73122. BCR crosslinking in Lrba-/- B cells resulted in poor p50 phosphorylation and p65 nuclear localization. Increased levels of Nur77 were detected.DiscussionThese results indicate the importance of Lrba in controlling NF-κB activation driven by BCR. Basal activation of NF-κB could impact cellular processes, such as, activation, differentiation, proliferation, and maintenance of B cells after antigen encounter
Rola Ducha Świętego w kaznodziejstwie protestanckim
No full textWithin Protestantism preaching is regarded as the main task of the Church. Lutheran theology sees in the sermon the presence of Christ and the source of the justifying faith born of hearing and accepting the word proclaimed, as well as the place of the Holy Spirit who promotes faith in those who hear the Gospel. For the father of the Reformation, Martin Luther, the work of the Holy Spirit is closely related to the Gospel which was inspired by Him and thanks to His support can be preached and heard at all. And according to John Calvin, the Holy Spirit is a true teacher (magister) and perpetrator (effector) who, as the proper author of the sermon, makes it a saving event.Assigning the Third Person of God a vital role in proclaiming the word of God gave birth to a question about what is the work of God in the sermon and what is the work of man. The search for such Protestant theologians in the 20th century as Rudolf Bohren, Manfred Josuttis and (late) Karl Barth led to the creation of the theory of preaching based on the pneumatological paradigm. It is an attempt to theologically justify the connection of the divine and human elementsin the sermon. It is in the Holy Spirit who wants to act in us and through us (the principle of the theonomical reciprocity), preaching, seen as completely lying in God’s possibilities, becomes the preacher’s thing and the thing of the listener, lies entirely in the possibilities of man (both skills and technique) – provided that both the preacher and the listener are openfor His actions. The pneumatological homiletics gave not only an answer to the question about the level of God’s and man’s activity in the process of preaching, but also even more insightfully described the overwhelming role of the Holy Spirit in preaching.W obrębie protestantyzmu kaznodziejstwo traktowane jest jako główne zadanie Kościoła. Teologia luterańska widzi w kazaniu uobecnienie Chrystusa i źródło usprawiedliwiającej wiary rodzącej się ze słuchania i przyjęcia głoszonego słowa, jak też miejsce działania Ducha Świętego, który wznieca wiarę w tych, którzy słuchają Ewangelii. Dla ojca reformacji, Marcina Lutra, działanie Ducha Świętego jest ściśle związane z Ewangelią, która została przez Niego natchniona i dzięki Jego wsparciu może być w ogóle głoszona i słyszana. Zaś według Jana Kalwina, to Duch Święty jest prawdziwym nauczycielem (magister) i sprawcą (effector), który jako właściwy Autor kazania czyni zeń zbawcze wydarzenie.Przypisanie Trzeciej Osobie Boskiej istotnej roli w głoszeniu słowa Bożego zrodziło pytanie o to, co w kazaniu jest dziełem Boga, a co dziełem człowieka. Poszukiwania w tej materii takich dwudziestowiecznych teologów protestanckich jak Rudolf Bohren, Manfred Josuttis czy (późny) Karl Barth, doprowadziły do stworzenia teorii kaznodziejstwa opartej na paradygmacie pneumatologicznym. Jest ona próbą teologicznego uzasadnienia połączenia elementu boskiego i ludzkiego w kazaniu. To w Duchu Świętym, który chce działać w nas i poprzez nas (zasada teonomicznej obopólności), kaznodziejstwo, widziane jako leżące całkowicie w możliwościach Boga, staje się całkowicie rzeczą kaznodziei i rzeczą słuchacza, leży całkowicie w możliwościach człowiekazarówno w sztuce, jak i technice – pod warunkiem, że zarówno kaznodzieja, jak i słuchacz będą otwarci na Jego działanie. Homiletyka pneumatologiczna dała nie tylko odpowiedź na pytanie o stopień aktywności Boga i człowieka w procesie kazania, lecz także jeszcze wnikliwiej opisała przemożną rolę Ducha Świętego w kaznodziejstwie
Identification of two new μ-adaptin-related proteins, μ-ARP1 and μ-ARP2
No full textAbstractWe report the cDNA cloning, primary structure and tissue distribution of two new proteins homologous to μ-adaptins, the medium chains of the clathrin coat adaptor complexes. Both predicted proteins share 60% amino acid sequence identity with each other and 27–31% identity with μ1-adaptin (ap47) and μ2-adaptin (ap50). Lower similarity (23–25% identity) is found with two other μ-adaptin-related proteins, p47A/B, and there is similarity over the N-terminal 150 amino acids with the adaptin small chains and δ-COP. The mRNAs of both molecules are expressed in all tissues analyzed, but with different profiles of relative abundance. μ-ARP1 is most abundant in brain, ovary and lung, whereas μ-ARP2 is prominently expressed in testis. These proteins suggest the existence of as yet uncharacterized types of clathrin- or non-clathrin-associated protein coats in cellular membrane traffic, of which they are probably prototype subunits, and provide molecular markers and probes for their characterization
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