The role of clathrin in post-golgi trafficking in toxoplasma gondii

Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle

Biogenesis of the inner membrane complex is dependent on vesicular transport by the alveolate specific GTPase Rab11B

Apicomplexan parasites belong to a recently recognised group of protozoa referred to as Alveolata. These protists contain membranous sacs (alveoli) beneath the plasma membrane, termed the Inner Membrane Complex (IMC) in the case of Apicomplexa. During parasite replication the IMC is formed de novo within the mother cell in a process described as internal budding. We hypothesized that an alveolate specific factor is involved in the specific transport of vesicles from the Golgi to the IMC and identified the small GTPase Rab11B as an alveolate specific Rab-GTPase that localises to the growing end of the IMC during replication of Toxoplasma gondii. Conditional interference with Rab11B function leads to a profound defect in IMC biogenesis, indicating that Rab11B is required for the transport of Golgi derived vesicles to the nascent IMC of the daughter cell. Curiously, a block in IMC biogenesis did not affect formation of sub-pellicular microtubules, indicating that IMC biogenesis and formation of sub-pellicular microtubules is not mechanistically linked. We propose a model where Rab11B specifically transports vesicles derived from the Golgi to the immature IMC of the growing daughter parasites

Resveratrol inhibits nonalcoholic fatty liver disease in rats

<p>Abstract</p> <p>Background</p> <p>The prevalence of nonalcoholic fatty liver disease (NAFLD) is high. NAFLD is linked to obesity, diabetes mellitus, and hypertriglyceridemia. Approximately 20% of patients with NAFLD will eventually develop cirrhosis. Our purpose was to investigate whether resveratrol decreased hepatic steatosis in an animal model of steatosis, and whether this therapeutic approach resulted in a decrease in tumor necrosis factor α (TNF-α) production, lipid peroxidation and oxidative stress.</p> <p>Methods</p> <p>Male Wistar CRL: Wi (Han) (225 g) rats were randomized into three groups. A control group (n = 12) was given free access to regular dry rat chow for 4 weeks. The steatosis (n = 12) and resveratrol (n = 12) groups were given free access to feed (a high carbohydrate-fat free modified diet) and water 4 days per week, and fasted for the remaining 3 days for 4 weeks. Rats in the resveratrol group were given resveratrol 10 mg daily by the oral route. All rats were killed at 4 weeks and assessed for fatty infiltration and bacterial translocation. Levels of TNF-α in serum, hepatic malondialdehyde (MDA), oxidative stress (superoxide dismutase, glutathione peroxidase, catalase and nitric oxide synthase) and biochemical parameters were measured.</p> <p>Results</p> <p>Fat deposition was decreased in the resveratrol group as compared to the steatosis group (Grade 1 vs Grade 3, P < 0.05). TNF-α and MDA levels were significantly increased in the steatosis group (TNF-α; 33.4 ± 5.2 vs 26.24 ± 3.47 pg/ml and MDA; 9.08 ± 0.8 vs 3.17 ± 1.45 μM respectively, <it>P </it>< 0.05). This was accompanied by increased superoxide dismutase, glutathione peroxidase and catalase and decreased nitric oxide synthase in the liver of resveratrol group significantly (<it>P </it>< 0.05 vs steatosis group). Bacterial translocation was not found in any of the groups. Glucose levels were decreased in the group of rats given resveratrol (<it>P </it>< 0.05).</p> <p>Conclusion</p> <p>Resveratrol decreased NAFLD severity in rats. This effect was mediated, at least in part, by TNF-α inhibition and antioxidant activities.</p

Criteria for evaluation of disease extent by 123I-metaiodobenzylguanidine scans in neuroblastoma: a report for the International Neuroblastoma Risk Group (INRG) Task Force

BackgroundNeuroblastoma is an embryonic tumour of the sympathetic nervous system, metastatic in half of the patients at diagnosis, with a high preponderance of osteomedullary disease, making accurate evaluation of metastatic sites and response to therapy challenging. Metaiodobenzylguanidine (mIBG), taken into cells via the norepinephrine transporter, provides a sensitive and specific method of assessing tumour in both soft tissue and bone sites. The goal of this report was to develop consensus guidelines for the use of mIBG scans in staging, response assessment and surveillance in neuroblastoma.MethodsThe International Neuroblastoma Risk Group (INRG) Task Force, including a multidisciplinary group in paediatric oncology of North and South America, Europe, Oceania and Asia, formed a subcommittee on metastatic disease evaluation, including expert nuclear medicine physicians and oncologists, who developed these guidelines based on their experience and the medical literature, with approval by the larger INRG Task Force.ResultsGuidelines for patient preparation, radiotracer administration, techniques of scanning including timing, energy, specific views, and use of single photon emission computed tomography are included. Optimal timing of scans in relation to therapy and for surveillance is reviewed. Validated semi-quantitative scoring methods in current use are reviewed, with recommendations for use in prognosis and response evaluation.ConclusionsMetaiodobenzylguanidine scans are the most sensitive and specific method of staging and response evaluation in neuroblastoma, particularly when used with a semi-quantitative scoring method. Use of the optimal techniques for mIBG in staging and response, including a semi-quantitative score, is essential for evaluation of the efficacy of new therapy

SIRT1 Undergoes Alternative Splicing in a Novel Auto-Regulatory Loop with p53

Background: The NAD-dependent deacetylase SIRT1 is a nutrient-sensitive coordinator of stress-tolerance, multiple homeostatic processes and healthspan, while p53 is a stress-responsive transcription factor and our paramount tumour suppressor. Thus, SIRT1-mediated inhibition of p53 has been identified as a key node in the common biology of cancer, metabolism, development and ageing. However, precisely how SIRT1 integrates such diverse processes remains to be elucidated. Methodology/Principal Findings: Here we report that SIRT1 is alternatively spliced in mammals, generating a novel SIRT1 isoform: SIRT1-DExon8. We show that SIRT1-DExon8 is expressed widely throughout normal human and mouse tissues, suggesting evolutionary conservation and critical function. Further studies demonstrate that the SIRT1-DExon8 isoform retains minimal deacetylase activity and exhibits distinct stress sensitivity, RNA/protein stability, and protein-protein interactions compared to classical SIRT1-Full-Length (SIRT1-FL). We also identify an auto-regulatory loop whereby SIRT1-DExon8 can regulate p53, while in reciprocal p53 can influence SIRT1 splice variation. Conclusions/Significance: We characterize the first alternative isoform of SIRT1 and demonstrate its evolutionary conservation in mammalian tissues. The results also reveal a new level of inter-dependency between p53 and SIRT1, two master regulators of multiple phenomena. Thus, previously-attributed SIRT1 functions may in fact be distributed betwee

Nuclear medicine procedures in neuroblastoma

In NB diagnostic setting, nuclear medicine procedures have demonstrated major accuracy for both staging and treatment response assessments, including the evaluation of bone and bone marrow involvement. 123I-MIBG scintigraphy has been extensively used in research and clinical practice for over 35 years, representing the most important functional imaging modality in NB assessment. Furthermore, therapy with 131I-MIBG has been extensively employed in neuroblastoma since the late 1980s, with a systematic review analyzing 1121 patients treated with 131I-MIBG. 131I-MIBG was used as single agent (monotherapy) in patients with a poor prognosis, in particular those with recurrent/refractory disease, as a palliative treatment. So far, 131I-MIBG therapy is included in multicentric trials on high-risk neuroblastoma patients. However, in recent years, different types of “new” PET tracers have been introduced in the diagnostic workup of NB showing very promising results [21, 22]. In this new diagnostic scenario, it seems important to identify strengths and limitation of each different functional diagnostic modality. The aim of this chapter is to analyze, in terms of availability and accuracy, the principal nuclear medicine procedures used in NB. In addition, the prevalent or complementary role of each functional imaging method is highlighted