Transmission clustering drives the onward spread of the HIV epidemic among men who have sex with men in Quebec

Phylodynamic analysis and epidemiologic data identified 3 patterns of spread of primary human immunodeficiency virus type 1 infection (PHI) among men who have sex with men (2001-2009): 420 unique PHIs, 102 small clusters (2-4 PHIs per cluster, n = 280), and 46 large clusters (5-31 PHIs per cluster, n = 450). Large clusters disproportionately increased from 25.2% of PHIs in 2005 to 39.1% in 2009 (χ(2) = 33.9, P < .001). Scalar expansion of large clusters over 11 months (interquartile range, 3.5-25.5 months) correlated with cluster membership size (r(2) = 0.174, F = 4.424, P = .047). PHI cohort data revealed variations in social networks and risk behaviors among the 3 groups, suggesting the need for tailored prevention measures.     

Frontotemporal Dementia: From Mendelian Genetics Towards Genome Wide Association Studies

Frontotemporal lobar degeneration is the most common cause of dementia of non-Alzheimer's type worldwide. It manifests, clinically, with behavioural changes and language impairment and is pathologically associated with tau- or ubiquitin-positive inclusions detected in neurons and glial cells of the frontal and temporal lobes in the brain. Genetic variations in the microtubule-associated protein tau and progranulin genes explain almost 50% of familial cases, whilst variations in TAR DNA-binding protein, charged multivescicular body protein 2B, valosin-containing protein and fused in sarcoma genes contribute to <5% of cases. The rapidly developing investigative techniques available to geneticists such as genome-wide association studies, whole-exome sequencing and, soon, whole-genome sequencing promise to contribute to the unravelling of the genetic architecture of this complex disease and, in the future, to the development of more sensitive, accurate and effective diagnostic and treatment measures.     

Indian‐subcontinent NBIA: Unusual phenotypes,novel PANK2 mutations,and undetermined genetic forms

Neurodegeneration with brain iron accumulation (NBIA) is etiologically, clinically, and by imaging a heterogeneous group including NBIA types 1 [pantothenate kinase‐associated neurodegeneration (PKAN)] and 2 (PLA2G6‐associated neurodegeneration), neuroferritinopathy, and aceruloplasminaemia. Data on genetically defined Indian‐subcontinent NBIA cases are limited. We report 6 patients from the Indian‐subcontinent with a movement disorder and MRI basal ganglia iron deposition, compatible with diagnosis of an NBIA syndrome. All patients were screened for abnormalities in serum ceruloplasmin and ferritin levels and mutations in NBIA‐associated genes [pantothenate kinase 2 (PANK2), PLA2G6 and ferritin light chain (exon 4)]. We present clinical, imaging and genetic data correlating phenotype–genotype relations. Four patients carried PANK2 mutations, two of these were novel. The clinical phenotype was mainly dystonic with generalized dystonia and marked orobulbar features in the 4 adolescent‐onset cases. One of the four had a late‐onset (age 37) unilateral jerky postural tremor. His mutation, c.1379C>T, appears associated with a milder phenotype. Interestingly, he developed the eye‐of‐the‐tiger sign only 10 years after onset. Two of the six presented with adult‐onset levodopa (L ‐dopa)‐responsive asymmetric re‐emergent rest tremor, developing L ‐dopa‐induced dyskinesias, and good benefit to deep brain stimulation (in one), thus resembling Parkinson's disease (PD). Both had an eye‐of‐the‐tiger sign on MRI but were negative for known NBIA‐associated genes, suggesting the existence of further genetic or sporadic forms of NBIA syndromes. In conclusion, genetically determined NBIA cases from the Indian subcontinent suggest presence of unusual phenotypes of PANK2 and novel mutations. The phenotype of NBIA of unknown cause includes a PD‐like presentation. © 2010 Movement Disorder Society     

Peptide-binding heat shock protein GRP78 protects cardiomyocytes from hypoxia-induced apoptosis

Myocardial ischemia is a severe stress condition that causes extensive biochemical changes triggering cardiac cell death. The 78-kDa glucose-regulated protein (GRP78), a heat shock protein present in all cells and a widely used marker of endoplasmic reticulum stress, functions in controlling the structural maturation of nascent glycoproteins. However, GRP78 was also found to be expressed on the cell surface of several cells such as endothelial cells, macrophages, and tumor cells where it functions as a receptor for a variety of ligands in signaling pathways. Recently, we have identified peptides from two different sources that specifically bind GRP78 protein. We have shown that binding of these peptides to endothelial cell surface GRP78 resulted in angiogenesis. In this study, we first established the presence of cell surface GRP78 on cardiac myocytes. Analysis of cardiomyocytes under hypoxia determined the significant increase in cell surface GRP78 in addition to gene expression and total protein. Apoptosis that was significantly increased in cardiomyocytes under hypoxic conditions was inhibited by the presence of the peptide-binding GRP78 during hypoxia. Inhibition of apoptosis was mediated by the binding of the peptide to cardiomyocytes cell surface GRP78 resulting in blocking caspase-3/7 activation. Silencing GRP78 RNA that reduced GRP78 receptor abrogated the peptide activity. Apoptosis of cardiac cells induced by myocardial infarction in a mouse model was also significantly inhibited by the administration of the peptide to mouse hearts. Our findings may make ADoPep1 a useful therapeutic tool for relieving of ischemia.     

Cytotoxicity of the Bacillus cereus Nhe Enterotoxin Requires Specific Binding Order of Its Three Exoprotein Components

This study focuses on the interaction of the three components of the Bacillus cereus Nhe enterotoxin with particular emphasis on the functional roles of NheB and NheC. The results demonstrated that both NheB and NheC were able to bind to Vero cells directly while NheA lacked this ability. It was also shown that Nhe-induced cytotoxicity required a specific binding order of the individual components whereby the presence of NheC in the priming step as well as the presence of NheA in the final incubation step was mandatory. Priming of cells with NheB alone and addition of NheA plus NheC in the second step failed to induce toxic effects. Furthermore, in solution, excess NheC inhibited binding of NheB to Vero cells, whereas priming of cells with excess NheC resulted in full toxicity if unbound NheC was removed before addition of NheB. By using mutated NheC proteins where the two cysteine residues in the predicted β-tongue were replaced with glycine (NheC_cys−) or where the entire hydrophobic stretch was deleted (NheC_hr−), the predicted hydrophobic β-tongue of NheC was found essential for binding to cell membranes but not for interaction with NheB in solution. All data presented here are compatible with the following model. The first step in the mode of action of Nhe is associated with binding of NheC and NheB to the cell surface and probably accompanied by conformational changes. These events allow subsequent binding of NheA, leading to cell lysis.Bacillus cereus is a spore-forming rod-shaped bacterium, which is commonly present in food. This major food-borne pathogen is known to cause two different types of food poisoning (for reviews, see references 20 and 21), which are characterized by either emesis or diarrhea. As putative agents for the diarrheal type of illness, two different protein complexes, hemolysin BL (Hbl) and nonhemolytic enterotoxin (Nhe) (3, 14), each consisting of three exoproteins, as well as a single protein (cytotoxin K [13]), have been identified. Nhe, described by Lund and Granum (14), contains the protein components NheA (41.0 kDa), NheB (39.8 kDa), and NheC (36.5 kDa). The genes encoding the three components of the Nhe complex have been cloned, and the entire operon has been characterized (10, 11). The significance of these three component toxins of Nhe and Hbl in enterotoxicity remains unclear. However, Moravek et al. (16) have shown by quantitative enterotoxin analyses that Nhe expression levels account for most of the B. cereus-associated cytotoxic activity.Little is known about the underlying mode of action of Nhe at the cellular level. Lindbäck et al. (11) showed that NheB binds to Vero cells and that the maximum cytotoxic activity in Vero cells was obtained when the molar ratio between NheA, -B, and -C was 10:10:1. Using B. cereus strain NVH 0075/95, it was shown that Nhe acts as a pore-forming toxin inducing cell lysis (9). Based on the crystal structure of the B component of the homologous three-component Hbl toxin (2, 15), sequence identities between all six Hbl and Nhe proteins indicate that NheB and NheC (9) show strong structural similarities to ClyA, a 34-kDa pore-forming hemolysin of several enteropathogenic Gram-negative Enterobacteriaceae (12, 19, 23). They all comprise a 4- to 5-helix bundle connected to a head subdomain with a characteristic hydrophobic β-tongue (24). In addition, functional similarities exist between the Nhe complex and ClyA, namely, formation of large conductance pores as well as cytolytic and hemolytic activity (9). In ClyA significant changes in conformation during membrane insertion and pore assembly have been predicted from electron microscopic measurements (8, 22) and the assembly mechanism of the alpha-helical pore has been recently unraveled (17).We hypothesized that these recent publications could serve as a framework for understanding Nhe action, particularly for the role of NheB and NheC. There is, however, one major difference, namely, that ClyA is a homo-oligomeric pore former whereas Nhe requires three related proteins for toxicity. Therefore, we dissected the natural working mechanism into single steps. By addition of the single components or combinations of two components in consecutive order, it was possible to demonstrate a specific binding order necessary to achieve toxic activity. In contrast to earlier studies, both NheB and NheC were identified as binding components, whereby the hydrophobic β-tongue of NheC was essential for binding to Vero cells but not necessary in the interaction with NheB. Interaction between NheB and NheC seems to occur mainly in solution, and binding of these two components was a prerequisite to allow action of the third component (NheA), leading to cell lysis.     

Molecular pathways: vasculogenic mimicry in tumor cells: diagnostic and therapeutic implications

Tumor cell vasculogenic mimicry (VM) describes the functional plasticity of aggressive cancer cells forming de novo vascular networks, thereby providing a perfusion pathway for rapidly growing tumors, transporting fluid from leaky vessels, and/or connecting with endothelial-lined vasculature. The underlying induction of VM seems to be related to hypoxia, which may also promote the plastic, transendothelial phenotype of tumor cells capable of VM. Since its introduction in 1999 as a novel paradigm for melanoma tumor perfusion, many studies have contributed new insights into the underlying molecular pathways supporting VM in a variety of tumors, including melanoma, glioblastoma, carcinomas, and sarcomas. In particular, critical VM-modulating genes are associated with vascular (VE-cadherin, EphA2, VEGF receptor 1), embryonic and/or stem cell (Nodal, Notch4), and hypoxia-related (hypoxia-inducible factor, Twist1) signaling pathways. Each of these pathways warrants serious scrutiny as potential therapeutic, vascular targets, and diagnostic indicators of plasticity, drug resistance, and the aggressive metastatic phenotype.