Quaternary dynamics and plasticity underlie small heat shock protein chaperone function

Small Heat Shock Proteins (sHSPs) are a diverse family of molecular chaperones that prevent protein aggregation by binding clients destabilized during cellular stress. Here we probe the architecture and dynamics of complexes formed between an oligomeric sHSP and client by employing unique mass spectrometry strategies. We observe over 300 different stoichiometries of interaction, demonstrating that an ensemble of structures underlies the protection these chaperones confer to unfolding clients. This astonishing heterogeneity not only makes the system quite distinct in behavior to ATP-dependent chaperones, but also renders it intractable by conventional structural biology approaches. We find that thermally regulated quaternary dynamics of the sHSP establish and maintain the plasticity of the system. This extends the paradigm that intrinsic dynamics are crucial to protein function to include equilibrium fluctuations in quaternary structure, and suggests they are integral to the sHSPs’ role in the cellular protein homeostasis network.     

Endonasal transsphenoidal surgery and multimodality treatment for giant pituitary adenomas

Objective Giant pituitary adenomas (≥40 mm) pose a major management challenge. We describe the experience of a single surgeon and a dedicated neuro‐endocrine team with multimodality treatment of these tumours in three specialized institutions. Design Retrospective data set analyses. Patients Fifty‐one consecutive patients with a giant adenoma (39 endocrine‐inactive, 12 endocrine‐active; mean tumour diameter 45 mm) treated over 10 years by an endonasal transsphenoidal approach were included. All patients had surgical resection followed by radiotherapy and/or medical therapy as judged necessary. Measurements Hormonal and visual status, extent of resection, tumour control rates, complications and use of medical and radiotherapy were evaluated. Results Surgery resulted in gross total, near total and subtotal removal in21 (41%), 10 (20%) and 20 (39%) patients respectively. Complete tumour removal was associated with absence of cavernous sinus invasion (P < 0·001). Long‐term endocrine function improved in 49% of patients and new endocrinopathy occurred in 14·6%; 76% required long‐term hormone replacement therapy. Vision improved in 81·5% of the patients and there was no visual worsening. At the last follow up (median 30 months), tumour control was achieved in 96% of patients: 59% with surgery alone, 20% with surgery plus focussed radiotherapy, 18% with surgery and medical therapy and two with all three modalities. Conclusions Endonasal surgery provides effective initial treatment for patients with giant adenomas. Multimodality therapy was needed in almost 50% of patients and this rate will likely increase with longer follow up. Close collaboration of neurosurgeons with endocrinologists and radiation oncologists is essential for optimal treatment of patients with these challenging tumours.     

Mouse MOV10L1 associates with Piwi proteins and is an essential component of the Piwi-interacting RNA (piRNA) pathway

Piwi-interacting RNAs (piRNAs) are essential for silencing of transposable elements in the germline, but their biogenesis is poorly understood. Here we demonstrate that MOV10L1, a germ cell–specific putative RNA helicase, is associated with Piwi proteins. Genetic disruption of the MOV10L1 RNA helicase domain in mice renders both MILI and MIWI2 devoid of piRNAs. Absence of a functional piRNA pathway in Mov10l1 mutant testes causes loss of DNA methylation and subsequent derepression of retrotransposons in germ cells. The Mov10l1 mutant males are sterile owing to complete meiotic arrest. This mouse mutant expresses Piwi proteins but lacks piRNAs, suggesting that MOV10L1 is required for piRNA biogenesis and/or loading to Piwi proteins.     

Association between basal, squamous cell carcinomas, dysplastic nevi and myotonic muscular dystrophy indicates an important role of RNA-binding proteins in development of human skin cancer

Myotonic muscular dystrophy (MMD) is caused by an abnormal function of RNA-binding proteins (RBP) resulting in DNA spliceopathy. A case of a patient, with MMD multiple basal and squamous cell carcinomas and dysplastic nevi, is described. The association between MMD and non-melanoma skin cancer has been reported before; however, this association was described before the genetic defect of myotonic dystrophy has been fully elucidated. The author proposes a genetic mechanism on how abnormal function of RBP can result or contribute to the development of human skin cancer and propose an explanation for this association between MMD and cutaneous carcinogenesis.     

Education is associated with reduction in racial disparities in kidney transplant outcome

In this study, we hypothesized that higher level of education might be associated with reduced racial disparities in renal transplantation outcomes. We used data from the United States Renal Data System (September 1, 1990–September 1, 2007) (n = 79 223) and analyzed two outcomes, graft loss and recipient mortality, using Cox models. Compared with whites, African Americans had increased risk of graft failure (HR, 1.48; p < 0.001) and recipient mortality (HR, 1.06; p = 0.004). Compared with recipients who graduated from college, all other education groups had inferior graft survival. Specifically, compared with college‐graduated individuals, African Americans who never finished high school had the highest risk of graft failure (HR, 1.45; p < 0.001), followed by high school graduates (HR, 1.27; p < 0.001) and those with some college education (HR, 1.18; p < 0.001). A similar trend was observed in whites. In African Americans (compared with whites), the highest risk of graft failure was associated with individuals who did not complete high school (HR, 1.96; p < 0.001) followed by high school graduates (HR, 1.47; p < 0.001), individuals with some college education (HR, 1.45; p < 0.001), and college graduates (HR, 1.39; p < 0.001). A similar trend was observed with recipient mortality. In sum, higher education was associated with reduced racial disparities in graft and recipient survival.     

Molecular identification and typing of Mycobacterium massiliense isolated from postsurgical infections in Brazil

ObjectiveOne hundred thirty-one cases of postsurgical infections were reported in Southern Region of Brazil between August 2007 and January 2008. Thirty-nine (29.8%) cases were studied; this report describes epidemiological findings, species identification, antimicrobial susceptibility and clonal diversity of rapidly growing mycobacteria isolated in this outbreak.MethodsAll 39 isolates were analyzed by Ziehl-Nielsen stained smear, bacterial culture and submitted to rpoB partial gene sequencing for identification. The isolates were also evaluated for their susceptibility to amikacin, cefoxitin, clarithromycin, ciprofloxacin, doxycycline, tobramycin and sulfamethoxazole.ResultsThirty-six isolates out of the confirmed cases were identified as Mycobacterium massiliense and the remaining three were identified as Mycobacterium abscessus, Mycobacterium chelonae and Mycobacterium fortuitum. All M. massiliense isolates were susceptible to amikacin (MIC₉₀ = 8 μg/mL) and clarithromycin (MIC₉₀ = 0.25 μg/mL) but resistant to cefoxitin, ciprofloxacin, doxycycline, tobramycin and sulfamethoxazole. Molecular analysis by pulsed-field gel electrophoresis clustered all 36 M. massiliense isolates and showed the same pattern (BRA 100) observed in three other outbreaks previously reported in Brazil.ConclusionsThese findings suggest a common source of infection for all patients and reinforce the hypotheses of spread of M. massiliense BRA100 in Brazilian hospital surgical environment in recent years.     

Nuclear DNA replication and repair in parasites of the genus Leishmania: Exploiting differences to develop innovative therapeutic approaches

Leishmaniasis is a common tropical disease that affects mainly poor people in underdeveloped and developing countries. This largely neglected infection is caused by Leishmania spp, a parasite from the Trypanosomatidae family. This parasitic disease has different clinical manifestations, ranging from localized cutaneous to more harmful visceral forms. The main limitations of the current treatments are their high cost, toxicity, lack of specificity, and long duration. Efforts to improve treatments are necessary to deal with this infectious disease. Many approved drugs to combat diseases as diverse as cancer, bacterial, or viral infections take advantage of specific features of the causing agent or of the disease. Recent evidence indicates that the specific characteristics of the Trypanosomatidae replication and repair machineries could be used as possible targets for the development of new treatments. Here, we review in detail the molecular mechanisms of DNA replication and repair regulation in trypanosomatids of the genus Leishmania and the drugs that could be useful against this disease.     

Monitoring of gliomas in vivo by diffusion MRI and 1H MRS during gene therapy‐induced apoptosis: interrelationships between water diffusion and mobile lipids

The measurement of water diffusion by diffusion‐weighted MRI (DWI) in vivo offers a non‐invasive method for assessing tissue responses to anti‐cancer therapies. The pathway of cell death after anti‐cancer treatment is often apoptosis, which leads to accumulation of mobile lipids detectable by ¹H MRS in vivo. However, it is not known how these discrete MR markers of cell death relate to each other. In a rodent tumour model [i.e. ganciclovir‐treated herpes simplex thymidine kinase (HSV‐tk) gene‐transfected BT4C gliomas], we studied the interrelationships between water diffusion (Trace{D}) and mobile lipids during apoptosis. Water diffusion and water‐referenced concentrations of mobile lipids showed clearly increasing and interconnected trends during treatment. Of the accumulating ¹H MRS‐visible lipids, the fatty acid ? CH ?CH ? groups and cholesterol compounds showed the strongest associations with water diffusion (r² = 0.30; P < 0.05 and r² = 0.48; P < 0.01, respectively). These results indicate that the tumour histopathology and apoptotic processes during tumour shrinkage can be interrelated in vivo by DWI of tissue water and ¹H MRS of mobile lipids, respectively. However, there is considerable individual variation in the associations, particularly at the end of the treatment period, and in the relative compositions of the accumulating NMR‐visible lipids. The findings suggest that the assessment of individual treatment response in vivo may benefit from combining DWI and ¹H MRS. Absolute and relative changes in mobile lipids may indicate initiation of tumour shrinkage even when changes in tissue water diffusion are still small. Conversely, greatly increased water diffusion probably indicates that substantial cell decomposition has taken place in the tumour tissue when the ¹H MRS resonances of mobile lipids alone can no longer give a reliable estimate of tissue conditions. Copyright © 2008 John Wiley & Sons, Ltd.