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Kuiper M.J.,University of Melbourne | Morton C.J.,St Vincents Institute Of Medical Research | Abraham S.E.,University of Melbourne | Gray-Weale A.,University of Melbourne
eLife | Year: 2015

Antifreeze proteins (AFPs) protect certain cold-adapted organisms from freezing to death by selectively adsorbing to internal ice crystals and inhibiting ice propagation. The molecular details of AFP adsorption-inhibition is uncertain but is proposed to involve the Gibbs–Thomson effect. Here we show by using unbiased molecular dynamics simulations a protein structure-function mechanism for the spruce budworm Choristoneura fumiferana AFP, including stereo-specific binding and consequential melting and freezing inhibition. The protein binds indirectly to the prism ice face through a linear array of ordered water molecules that are structurally distinct from the ice. Mutation of the ice binding surface disrupts water-ordering and abolishes activity. The adsorption is virtually irreversible, and we confirm the ice growth inhibition is consistent with the Gibbs–Thomson law. © 2015, eLife Sciences Publications Ltd. All rights reserved. Source

Heraud-Farlow J.E.,St Vincents Institute Of Medical Research | Walkley C.R.,St Vincents Institute Of Medical Research | Walkley C.R.,University of Melbourne
Journal of Molecular Medicine | Year: 2016

The innate immune system is the first line of the cellular defence against invading pathogens. A critical component of this defence is the capacity to discriminate foreign RNA molecules, which are distinct from most cellular RNAs in structure and/or modifications. However, a series of rare autoimmune/autoinflammatory diseases in humans highlight the propensity for the innate immune sensing system to be activated by endogenous cellular double-stranded RNAs (dsRNAs), underscoring the fine line between distinguishing self from non-self. The RNA editing enzyme ADAR1 has recently emerged as a key regulator that prevents innate immune pathway activation, principally the cytosolic dsRNA sensor MDA5, from inducing interferon in response to double-stranded RNA structures within endogenous RNAs. Adenosine-to-Inosine RNA editing by ADAR1 is proposed to destabilise duplexes formed from inverted repetitive elements within RNAs, which appear to prevent MDA5 from sensing these RNA as virus-like in the cytoplasm. Aberrant activation of these pathways has catastrophic effects at both a cellular and organismal level, contributing to one of the causes of the conditions collectively known as the type I interferonopathies. © 2016 Springer-Verlag Berlin Heidelberg Source

Shah M.H.,St Vincents Institute Of Medical Research | Liu G.-S.,University of Melbourne | Liu G.-S.,OBrien Institute | Thompson E.W.,St Vincents Institute Of Medical Research | And 4 more authors.
Breast Cancer Research and Treatment | Year: 2015

Reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (H2O2) have been implicated in development and progression of breast cancer. In the present study, we have evaluated the effects of the superoxide dismutase (SOD) mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 on superoxide and H2O2 formation as well as proliferation, adhesion, and migration of MCF-7 and MDA-MB-231 cells. Superoxide and H2O2 production was examined using dihydroethidium and Amplex red assays, respectively. Cell viability and adhesion were measured using a tetrazolium-based MTT assay. Cell proliferation was determined using trypan blue assay. Cell cycle progression was analyzed using flow cytometry. Clonal expansion of a single cell was performed using a colony formation assay. Cell migration was measured using transwell migration assay. Dual luciferase assay was used to determine NF-κB reporter activity. EUK 134 effectively reduced both superoxide and H2O2, whereas MnTmPyP removed superoxide but enhanced H2O2 formation. EUK 134 effectively attenuated viability, proliferation, clonal expansion, adhesion, and migration of MCF-7 and MDA-MB-231 cells. In contrast, MnTmPyP only reduced clonal expansion of MCF-7 and MDA-MB-231 cells but had no effect on adhesion and cell cycle progression. Tumor necrosis factor-alpha-induced NF-κB activity was reduced by EUK 134, whereas MnTmPyP enhanced this activity. These data indicate that the SOD mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 exert differential effects on breast cancer cell growth. Inhibition of H2O2 signaling using EUK 134-like compound might be a promising approach to breast cancer therapy. © 2015, Springer Science+Business Media New York. Source

Bouter Y.,University of Gottingen | Noguerola J.S.L.,University of Gottingen | Tucholla P.,University of Gottingen | Crespi G.A.N.,St Vincents Institute Of Medical Research | And 6 more authors.
Acta Neuropathologica | Year: 2015

Solanezumab and Crenezumab are two humanized antibodies targeting Amyloid-β (Aβ) which are currently tested in multiple clinical trials for the prevention of Alzheimer’s disease. However, there is a scientific discussion ongoing about the target engagement of these antibodies. Here, we report the immunohistochemical staining profiles of biosimilar antibodies of Solanezumab, Crenezumab and Bapineuzumab in human formalin-fixed, paraffin-embedded tissue and human fresh frozen tissue. Furthermore, we performed a direct comparative immunohistochemistry analysis of the biosimilar versions of the humanized antibodies in different mouse models including 5XFAD, Tg4-42, TBA42, APP/PS1KI, 3xTg. The staining pattern with these humanized antibodies revealed a surprisingly similar profile. All three antibodies detected plaques, cerebral amyloid angiopathy and intraneuronal Aβ in a similar fashion. Remarkably, Solanezumab showed a strong binding affinity to plaques. We also reaffirmed that Bapineuzumab does not recognize N-truncated or modified Aβ, while Solanezumab and Crenezumab do detect N-terminally modified Aβ peptides Aβ4–42 and pyroglutamate Aβ3–42. In addition, we compared the results with the staining pattern of the mouse NT4X antibody that recognizes specifically Aβ4–42 and pyroglutamate Aβ3–42, but not full-length Aβ1–42. In contrast to the biosimilar antibodies of Solanezumab, Crenezumab and Bapineuzumab, the murine NT4X antibody shows a unique target engagement. NT4X does barely cross-react with amyloid plaques in human tissue. It does, however, detect cerebral amyloid angiopathy in human tissue. In Alzheimer mouse models, NT4X detects intraneuronal Aβ and plaques comparable to the humanized antibodies. In conclusion, the biosimilar antibodies Solanezumab, Crenezumab and Bapineuzumab strongly react with amyloid plaques, which are in contrast to the NT4X antibody that hardly recognizes plaques in human tissue. Therefore, NT4X is the first of a new class of therapeutic antibodies. © 2015, Springer-Verlag Berlin Heidelberg. Source

Joglekar M.V.,University of Sydney | Trivedi P.M.,St Vincents Institute Of Medical Research | Trivedi P.M.,University of Melbourne | Kay T.W.,St Vincents Institute Of Medical Research | And 8 more authors.
Apoptosis | Year: 2016

Cell death via FAS/CD95 can occur either by activation of caspases alone (extrinsic) or by activation of mitochondrial death signalling (intrinsic) depending on the cell type. The BH3-only protein BID is activated in the BCL-2-regulated or mitochondrial apoptosis pathway and acts as a switch between the extrinsic and intrinsic cell death pathways. We have previously demonstrated that islets from BID-deficient mice are protected from FAS ligand-mediated apoptosis in vitro. However, it is not yet known if BID plays a similar role in human beta cell death. We therefore aimed to test the role of BID in human islet cell apoptosis immediately after isolation from human cadaver donors, as well as after de-differentiation in vitro. Freshly isolated human islets or 10–12 day cultured human islet cells exhibited BID transcript knockdown after BID siRNA transfection, however they were not protected from FAS ligand-mediated cell death in vitro as determined by DNA fragmentation analysis using flow cytometry. On the other hand, the same cells transfected with siRNA for FAS-associated via death domain (FADD), a molecule in the extrinsic cell death pathway upstream of BID, showed significant reduction in cell death. De-differentiated islets (human islet-derived progenitor cells) also demonstrated similar results with no difference in cell death after BID knockdown as compared to scramble siRNA transfections. Our results indicate that BID-independent pathways are responsible for FAS-dependent human islet cell death. These results are different from those observed in mouse islets and therefore demonstrate potentially alternate pathways of FAS ligand-induced cell death in human and mouse islet cells. © 2016 Springer Science+Business Media New York Source

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