TorsinA and heat shock proteins act as molecular chaperones: suppression of alpha-synuclein aggregation

TorsinA, a protein with homology to yeast heat shock protein104, has previously been demonstrated to colocalize with alpha-synuclein in Lewy bodies, the pathological hallmark of Parkinson's disease. Heat shock proteins are a family of chaperones that are both constitutively expressed and induced by stressors, and that serve essential functions for protein refolding and/or degradation. Here, we demonstrate that, like torsinA, specific molecular chaperone heat shock proteins colocalize with alpha-synuclein in Lewy bodies. In addition, using a cellular model of alpha-synuclein aggregation, we demonstrate that torsinA and specific heat shock protein molecular chaperones colocalize with alpha-synuclein immunopositive inclusions. Further, overexpression of torsinA and specific heat shock proteins suppress alpha-synuclein aggregation in this cellular model, whereas mutant torsinA has no effect. These data suggest that torsinA has chaperone-like activity and that the disease-associated GAG deletion mutant has a loss-of-function phenotype. Moreover, these data support a role for chaperone proteins, including torsinA and heat shock proteins, in cellular responses to neurodegenerative inclusions.     

Neurotoxicity of nitroxyl: insights into HNO and NO biochemical imbalance

Nitroxyl anion (NO-), and/or its conjugate acid, HNO, may be formed in the cellular milieu by several routes under both physiological and pathophysiological conditions. Since experimental evidence suggests that certain reactive nitrogen oxide species can contribute significantly to cerebral ischemic injury, we investigated the neurotoxic potential of HNO/NO- using Angeli's salt (AS), a spontaneous HNO/NO(-)-generating compound. Exposure to AS resulted in a time- and concentration-dependent increase in neural cell death that progressed markedly following the initial exposure. Coadministration of the donor with Tempol (1 mM), a one-electron oxidant that converts NO- to NO, prevented its toxic effect, as did the concomitant addition of Fe(III)TPPS. Media containing various chelators, catalase, Cu/Zn superoxide dismutase, or carboxy-PTIO did not ameliorate AS-mediated neurotoxicity, ruling out the involvement of transition metal complexes, H2O2, O2-, and NO, respectively. A concentration-dependent increase in supernatant protein 3-nitrotyrosine immunoreactivity was observed when cultures were exposed to AS under aerobic conditions, an effect lost in the absence of oxygen. A bell-shaped curve for augmented AS-mediated nitration was observed with increasing Fe(III)TPPS concentration, which contrasted with its linear effect on abating cytotoxicity. Finally, addition of glutamate receptor antagonists, MK-801 (10 microM) and CNQX (30 microM) to the cultures abrogated toxicity when given during, but not following, AS exposure; as did pretreatment with the exocytosis inhibitor, tetanus toxin (300 ng/ml). Taken together, our data suggest that under aerobic conditions, AS toxicity is initiated via HNO/NO- but progresses via secondary excitotoxicity.     

Identifying Medical Diagnoses and Treatable Diseases by Image-Based Deep Learning

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Rejecting strictly allopatric speciation on a continental island: prolonged postdivergence gene flow between Taiwan (Leucodioptron taewanus,Passeriformes Timaliidae) and Chinese (L. canorum canorum) hwameis

Allopatry is conventionally considered the geographical mode of speciation for continental island organisms. However, strictly allopatric speciation models that assume the lack of postdivergence gene flow seem oversimplified given the recurrence of land bridges during glacial periods since the late Pliocene. Here, to evaluate whether a continental island endemic, the Taiwan hwamei (Leucodioptron taewanus, Passeriformes Timaliidae) speciated in strict allopatry, we used weighted‐regression‐based approximate Bayesian computation (ABC) to analyse the genetic polymorphism of 18 neutral nuclear loci (total length: 8500 bp) in Taiwan hwamei and its continental sister species, the Chinese hwamei (L. canorum canorum). The nonallopatry model was found to fit better with observed genetic polymorphism of the two hwamei species (posterior possibility = 0.82). We also recovered unambiguous signals of nontrivial bidirectional postdivergence gene flow (N_em » 1) between Chinese hwamei and Taiwan hwamei until 0.5 Ma. Divergence time was estimated to be 3.5 to 2 million years earlier than that estimated from mitochondrial cytochrome b sequences. Finally, using the inferred nonallopatry model to simulate genetic variation at 24 nuclear genes examined showed that the adiponectin receptor 1 gene may be under divergent adaptation. Our findings imply that the role of geographical barrier may be less prominent for the speciation of continental island endemics, and suggest a shift in speciation studies from simply correlating geographical barrier and genetic divergence to examining factors that facilitate and maintain divergence, e.g. differential selection and sexual selection, especially in the face of interpopulation gene flow.     

Identification of tumour-induced changes in endothelial cell surface protein expression: an in vitro model

The selective destruction of the supporting vasculature of tumours has been proposed as a means of therapy. Fundamental to this approach is the identification of suitable targets on tumour-endothelium. To detect proteins that may be up-regulated on the luminal (apical) surface of tumour-associated endothelium confluent endothelial cells were examined following incubation with tumour cell conditioned medium (TCM) from, or co-culture with, a range of breast carcinoma and small cell lung carcinoma (SCLC) cell lines. Exposed endothelial membrane proteins were labelled with sulpho-NHS-biotin and detected by enhanced chemiluminescence following two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and western blotting. TCM induced varying levels of proliferative activity in endothelial cells; generally breast TCM contained greater mitogenic activity than SCLC TCM. Exposure of human breast and lung microvascular, and umbilical vein endothelial cells to soluble tumour cell factors from several breast cancer and SCLC cells lines produced similar changes in luminal protein profiles: Breast cancer cells and in particular the MDA-MB-231 cell line induced the most pronounced changes. The expression of six proteins was altered consistently on endothelial cells stimulated with soluble tumour cell factors. However, similar changes were observed following incubation with ECGS suggesting that they were related to endothelial cell proliferation per se. As these proteins were altered in breast and lung microvascular, and umbilical vein endothelial cells stimulated by a variety of breast cancer and SCLC cell lines they support the potentially broad applicability of anti-vascular approaches targeted at the endothelium.     

Improved gold chloride staining method for anatomical analysis of sensory nerve endings in the shoulder capsule and labrum as examples of loose and dense fibrous tissues

Consistency in gold chloride staining is essential for anatomical analysis of sensory nerve endings. The gold chloride stain for this purpose has been modified by many investigators, but often yields inconsistent staining, which makes it difficult to differentiate structures and to determine nerve ending distribution in large tissue samples. We introduce additional steps and major changes to the modified Gairns’ protocol. We controlled the temperature and mixing rate during tissue staining to achieve consistent staining and complete solution penetration. We subjected samples to sucrose dehydration to improve cutting efficiency. We then exposed samples to a solution containing lemon juice, formic acid and paraformaldehyde to produce optimal tissue transparency with minimal tissue deformity. We extended the time for gold chloride impregnation 1.5 fold. Gold chloride was reduced in the labrum using 25% formic acid in water for 18 h and in the capsule using 25% formic acid in citrate phosphate buffer for 2 h. Citrate binds gold nanoparticles, which minimizes aggregation in the tissue. We stored samples in fresh ultrapure water at 4° C to slow reduction and to maintain color contrast in the tissue. Tissue samples were embedded in Tissue Tek and sectioned at 80 and 100 μm instead of using glycerin and teasing the tissue apart as in Gairns’ modified gold chloride method. We attached sections directly to gelatin subbed slides after sectioning with a cryostat. The slides then were processed and coverslipped with Permount. Staining consistency was demonstrated throughout the tissue sections and neural structures were clearly identifiable.     

VEGF-E activates endothelial nitric oxide synthase to induce angiogenesis via cGMP and PKG-independent pathways

Vascular endothelial growth factor-A (VEGF), which binds to both VEGF receptor-1 (Flt1) and VEGFR-2 (KDR/Flk-1), requires nitric oxide (NO) to induce angiogenesis in a cGMP-dependent manner. Here we show that VEGF-E, a VEGFR-2-selective ligand stimulates NO release and tube formation in human umbilical vein endothelial cells (HUVEC). Inhibition of phospholipase Cgamma (PLCgamma) with U73122 abrogated VEGF-E induced endothelial cell migration, tube formation and NO release. Inhibition of endothelial nitric oxide synthase (eNOS) using l-NNA blocked VEGF-E-induced NO release and angiogenesis. Pre-incubation of HUVEC with the soluble guanylate cyclase inhibitor, ODQ, or the protein kinase G (PKG) inhibitor, KT-5823, had no effect on angiogenesis suggesting that the action of VEGF-E is cGMP-independent. Our data provide the first demonstration that VEGFR-2-mediated NO signaling and subsequent angiogenesis is through a mechanism that is dependent on PLCgamma but independent of cGMP and PKG.