Commercially Available Angiotensin II At2 Receptor Antibodies Are Nonspecific

Commercially available angiotensin II AT₂ receptor antibodies are widely employed for receptor localization and quantification, but they have not been adequately validated. In this study, we characterized three commercially available AT₂ receptor antibodies: 2818-1 from Epitomics, sc-9040 from Santa Cruz Biotechnology, Inc., and AAR-012 from Alomone Labs. Using western blot analysis the immunostaining patterns observed were different for every antibody tested, and in most cases consisted of multiple immunoreactive bands. Identical immunoreactive patterns were present in wild-type and AT₂ receptor knockout mice not expressing the target protein. In the mouse brain, immunocytochemical studies revealed very different cellular immunoreactivity for each antibody tested. While the 2818-1 antibody reacted only with endothelial cells in small parenchymal arteries, the sc-9040 antibody reacted only with ependymal cells lining the cerebral ventricles, and the AAR-012 antibody reacted only with multiple neuronal cell bodies in the cerebral cortex. Moreover, the immunoreactivities were identical in brain tissue from wild-type or AT₂ receptor knockout mice. Furthermore, in both mice and rat tissue extracts, there was no correlation between the observed immunoreactivity and the presence or absence of AT₂ receptor binding or gene expression. We conclude that none of these commercially available AT₂ receptor antibodies tested met the criteria for specificity. In the absence of full antibody characterization, competitive radioligand binding and determination of mRNA expression remain the only reliable approaches to study AT₂ receptor expression.     

Expression of an amino acid biosynthesis gene in tomato flowers: developmental upregulation and MeJa response are parenchyma-specific and mutually compatible

The gene coding for threonine deaminase (TD), the enzyme which catalyzes the first committed step in the biosynthesis of isoleucine, was isolated from tomato as a consequence of its unusual 500-fold upregulation in floral organs. It was subsequently shown that TD is induced in potato leaves in response to wounding, abscisic acid and methyl jasmonate (MeJa). Detailed analysis presented here, reveals an intricate developmental regulation pattern of gene expression in flowers that is operating solely in parenchyma territories. Yet, despite its high pre-existing expression level, TD in flowers can be further induced by MeJa. Induction of TD in flowers as well as in leaves is effective only in the parenchyma domains, irrespective of the prior expression levels. TD is neither expressed nor induced in epidermal, vascular or sporogenous tissues. Promoter analysis in transgenic tomato plants indicates that induction of TD follows identical kinetics in flowers and leaves. Furthermore, the 'conditioning' of developmental upregulation in flowers, the response to MeJa in flowers and leaves, and the parenchyma-specific expression are all mediated by the cis -elements within the proximal 192 bp of the promoter. Promoter elements regulating the correct organ-specific expression are located, however, further upstream. The promoter constructs used in this study can serve as useful tools for expressing extremely high levels of transgenes in specific cells. A scheme explaining tissue-specific response to MeJa, in conjunction with developmental control, is discussed.     

TLR4 through IFN-β promotes low molecular mass hyaluronan-induced neutrophil apoptosis

Intratracheal administration of low molecular mass (LMM) hyaluronan (200 kDa) results in greater neutrophil infiltration in the lungs of TLR4(-/-) mice compared with that in wild-type mice. In general, enhanced neutrophil infiltration in tissue is due to cell influx; however, neutrophil apoptosis also plays an important role. We have assessed the effects of TLR4 in the regulation of neutrophil apoptosis in response to administration of LMM hyaluronan. We found that apoptosis of inflammatory neutrophils is impaired in TLR4(-/-) mice, an effect that depends upon the IFN-β-mediated TRAIL/TRAILR system. IFN-β levels were decreased in LMM hyaluronan-treated TLR4-deficient neutrophils. The treatment of inflammatory neutrophils with IFN-β enhanced the levels of TRAIL and TRAILR 2. LMM hyaluronan-induced inflammatory neutrophil apoptosis was substantially prevented by anti-TRAIL neutralizing mAb. We conclude that decreased IFN-β levels decrease the activity of the TRAIL/TRAILR system in TLR4-deficient neutrophils, leading to impaired apoptosis of neutrophils and resulting in abnormal accumulation of neutrophils in the lungs of LMM hyaluronan-treated mice. Thus, TLR4 plays a novel homeostatic role in noninfectious lung inflammation by accelerating the elimination of inflammatory neutrophils.     

A Typical Hospital-Acquired Methicillin-Resistant Staphylococcus aureus Clone Is Widespread in the Community in the Gaza Strip

Epidemiological data on community acquired methicillin-resistant-Staphylococcus aureus (CA-MRSA) carriage and infection in the Middle-East region is scarce with only few reports in the Israeli and Palestinian populations. As part of a Palestinian-Israeli collaborative research, we have conducted a cross-sectional survey of nasal S. aureus carriage in healthy children and their parents throughout the Gaza strip. Isolates were characterized for antibiotic susceptibility, mec gene presence, PFGE, spa type, SCCmec-type, presence of PVL genes and multi-locus-sequence-type (MLST). S. aureus was carried by 28.4% of the 379 screened children-parents pairs. MRSA was detected in 45% of S. aureus isolates, that is, in 12% of the study population. A single ST22-MRSA-IVa, spa t223, PVL-gene negative strain was detected in 64% of MRSA isolates. This strain is typically susceptible to all non-β-lactam antibiotics tested. The only predictor for MRSA carriage in children was having an MRSA carrier-parent (OR = 25.5, P = 0.0004). Carriage of the Gaza strain was not associated with prior hospitalization. The Gaza strain was closely related genetically to a local MSSA spa t223 strain and less so to EMRSA15, one of the pandemic hospital-acquired-MRSA clones, scarcely reported in the community. The rapid spread in the community may be due to population determinants or due to yet unknown advantageous features of this particular strain.     

Recurrent De Novo Dominant Mutations in SLC25A4 Cause Severe Early-Onset Mitochondrial Disease and Loss of Mitochondrial DNA Copy Number

Mutations in SLC25A4 encoding the mitochondrial ADP/ATP carrier AAC1 are well-recognized causes of mitochondrial disease. Several heterozygous SLC25A4 mutations cause adult-onset autosomal-dominant progressive external ophthalmoplegia associated with multiple mitochondrial DNA deletions, whereas recessive SLC25A4 mutations cause childhood-onset mitochondrial myopathy and cardiomyopathy. Here, we describe the identification by whole-exome sequencing of seven probands harboring dominant, de novo SLC25A4 mutations. All affected individuals presented at birth, were ventilator dependent and, where tested, revealed severe combined mitochondrial respiratory chain deficiencies associated with a marked loss of mitochondrial DNA copy number in skeletal muscle. Strikingly, an identical c.239G>A (p.Arg80His) mutation was present in four of the seven subjects, and the other three case subjects harbored the same c.703C>G (p.Arg235Gly) mutation. Analysis of skeletal muscle revealed a marked decrease of AAC1 protein levels and loss of respiratory chain complexes containing mitochondrial DNA-encoded subunits. We show that both recombinant AAC1 mutant proteins are severely impaired in ADP/ATP transport, affecting most likely the substrate binding and mechanics of the carrier, respectively. This highly reduced capacity for transport probably affects mitochondrial DNA maintenance and in turn respiration, causing a severe energy crisis. The confirmation of the pathogenicity of these de novo SLC25A4 mutations highlights a third distinct clinical phenotype associated with mutation of this gene and demonstrates that early-onset mitochondrial disease can be caused by recurrent de novo mutations, which has significant implications for the application and analysis of whole-exome sequencing data in mitochondrial disease.     

Non-autophagic GFP-LC3 puncta induced by saponin and other detergents

Expression of GFP-LC3 is now in widespread use to visualize autophagy in cultured cells. Recently, Kuma et al. (Autophagy 2007; 3:323-8) highlighted some complications using GFP-LC3, demonstrating that punctate dots containing GFP-LC3 do not always represent autophagic structures. We report here that GFP-LC3 can also rapidly aggregate into autophagosome look-alike structures when cells are permeabilized with saponin before cell fixation. Treatment with saponin reduced diffuse cytosolic and nuclear GFP-LC3 but caused an increase in the number and intensity of fluorescent puncta per cell regardless of whether the cells were induced to undergo autophagy. Saponin also induced GFP-LC3 puncta in Atg5(-/-) MEF transfected with GFP-LC3, where no LC3-II is produced, demonstrating that the puncta are autophagosome-independent. The increase in GFP-LC3 puncta was not matched by an increase in endogenous LC3-II or GFP-LC3-II detected by immunoblotting when protein samples were normalized to cell number. A qualitatively similar effect was observed when cells were treated with other detergents commonly used for membrane permeabilization, such as CHAPS, Triton X-100 or digitonin. We also noted that tubulin could not be used to normalize for protein loading on blots after applying saponin as it was selectively extracted from untreated cells but not from cells treated with vinblastine. When using mild detergents to remove background fluorescence, we recommend using a membrane-associated protein such as ATP synthase beta for normalization. Thus, detergents used prior to fixation may precipitate GFP-LC3 aggregation into structures that appear autophagosomal and so should be used with caution.     

Engineering Antigen-Specific T Cells from Genetically Modified Human Hematopoietic Stem Cells in Immunodeficient Mice

There is a desperate need for effective therapies to fight chronic viral infections. The immune response is normally fastidious at controlling the majority of viral infections and a therapeutic strategy aimed at reestablishing immune control represents a potentially powerful approach towards treating persistent viral infections. We examined the potential of genetically programming human hematopoietic stem cells to generate mature CD8+ cytotoxic T lymphocytes that express a molecularly cloned, “transgenic” human anti-HIV T cell receptor (TCR). Anti-HIV TCR transduction of human hematopoietic stem cells directed the maturation of a large population of polyfunctional, HIV-specific CD8+ cells capable of recognizing and killing viral antigen-presenting cells. Thus, through this proof-of-concept we propose that genetic engineering of human hematopoietic stem cells will allow the tailoring of effector T cell responses to fight HIV infection or other diseases that are characterized by the loss of immune control.