S100A1 acts positive inotropic and prevents Ca2+ triggered after-contractions in a model of Engineered Heart Tissue

The small calcium (Ca2+) binding protein S100A1 is as a critical regulator of cardiomyocyte Ca2+ handling thereby enhancing cardiac performance in vivo and in vitro. Our previous studies demonstrated that the positive inotropic effects of S100A1 are due to enhanced Ca2+ transients and sarcoplasmic reticulum (SR) Ca2+ load in isolated adult cardiomyocytes. These effects are independent of and in addition to cAMP-dependent positive inotropic mechanisms. However, inotropic interventions come at the risk of arrhythmogenic diastolic Ca2+ leakage when the SR Ca2+ content exceeds the threshold for spontaneous diastolic Ca2+ release. In a more recent study we could demonstrate that enhanced Ca2+ transients after S100A1 overexpression are associated with a reduced incidence of diastolic Ca2+ sparks and Ca2+ waves. These results favor the assumption that S100A1 might reduce the diastolic RyR2 leak, thereby impeding the development of pro-arrhythmogenic events. Thus, the aim of this work was to investigate the effect of S100A1 on diastolic Ca2+ handling and on the impact of Ca2+-triggered arrhythmias in a multicellular system. For this reason, the 3-dimensional tissue culture model of Engineered Heart Tissue (EHT) was chosen. Due to its syncytial architecture, EHT closely mimics functional alterations, intercellular communication and reverse remodeling of whole hearts in vivo despite eased handling and pharmacological as well as therapeutic manipulations. Pharmacological stimulation of EHT with endothelin-1 resulted in a heart failure-like phenotype with strong impairment of contractile performance. Adenoviral-mediated S100A1 overexpression was able to rescue failing EHT and resulted in superior contractility in normal EHT. Triggered contraction abnormalities, referred to as after-contractions, were induced by Ca2+ and β-AR stimulation and served as a surrogate of SOICR (store-overload-induced-Ca2+-release). S100A1 overexpression significantly protected against Ca2+ and β-adrenergic receptor (β-AR) triggered after-contractions in normal and failing EHT. Despite persistent abnormal phosphorylation-dependent changes at the RyR2 and altered complex formation with accessory proteins, S100A1 overexpression enhanced S100A1/RyR2 stoichiometry, which seems to be key for S100A1’s effects, combining inotropic and anti-arrhythmic potency

In Quest of the Good Urban Life: Socio-spatial Dynamics and Residential Building Stock Transformation in Zurich

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.This paper discusses socio-spatial dynamics and the transformation of the residential building stock in the global city of Zurich. It deals with five questions. Does Zurich exhibit the type of social polarisation outlined by the global city hypothesis? If so, how does social polarisation become visible in the context of a European city? Which actors in the real estate market are catering to the special tastes of the new urban middle class? With whom does the new middle class compete for space in the city? The paper argues that real estate developers customise the residential building stock and produce residential units for a targeted market—the new urban middle class. Furthermore, a new socio-spatial phenomenon—ennoblement—has evolved, as the new urban middle class takes residence in traditional upper-class neighbourhoods. By investing its own economic capital, this new middle class is hoping to profit from upper-class social and cultural capital

Multitasking of the RanBP2 complex - Protein SUMOylation and export complex disassembly

The essential, vertebrate-specific RanBP2/RanGAP1*SUMO1/Ubc9 complex is a fascinating macromolecular machine positioned at the nuclear pore complex during interphase. It is a unique composite SUMO E3 ligase and serves as a docking site for nuclear transport complexes. Moreover, the RanBP2 complex can stimulates Ran-GTP hydrolysis via its four Ran binding domains and the associated RanGAP activity. In the first part of this work, I wanted to obtain insight into the molecular mechanism of this composite E3 ligase. In order to unravel how it interacts with and activates its cognate E2 conjugating enzyme, I created a stable Ubc9∼SUMO thioester mimic that allowed in vitro interaction studies. I found evidence that SUMOylation via the RanBP2 complex depends on the formation of the catalytically productive, folded-back thioester conformation, similarly to ubiquitination. In collaboration with the group of Teresa Carlomagno (EMBL, Heidelberg), we mapped the interaction surfaces of the thioester mimic on the RanBP2 complex via NMR. Our analyses suggest that thioester-binding is not only achieved by the suspected interaction with RanBP2 itself, but also by a backside interaction between the SUMO1 molecule in the complex and the thioester-Ubc9. For this interaction, the complex opens up at its Ubc9/SUMO1-interface suggesting that it is not a static, but structurally dynamic entity during catalysis. In the second part of this work, I investigated possible roles of the RanBP2 complex for nuclear transport complexes, using a reconstituted version that contained RanGAP1, the SUMO E3 ligase region, two FG-repeat clusters and two Ran binding domains. I could show that the RanBP2 complex specifically binds and disassembles export complexes formed with the prototypic export receptor Crm1. The two FG-repeat clusters mediate RanBP2’s tight association with Crm1, which is followed by Ran binding domain-dependent cargo release and Ran-GTP hydrolysis. As the Crm1/RanBP2 interaction is compatible with RanBP2’s SUMO E3 ligase activity, my work also allows speculating about a possible Crm1-dependent substrate recruitment mechanism for the RanBP2 E3 ligase complex

Water Structures Reveal Local Hydrophobicity on the In2O3(111) Surface

Clean oxide surfaces are generally hydrophilic. Water molecules anchor at undercoordinated surface metal atoms that act as Lewis-acid sites, and they are stabilized by H bonds to undercoordinated surface oxygens. The large unit cell of In2O3(111) provides surface atoms in various configurations, which leads to chemical heterogeneity and a local deviation from this general rule. Experiments (TPD, XPS, ncAFM) agree quantitatively with DFT calculations and show a series of distinct phases. The first three water molecules dissociate at one specific area of the unit cell and desorb above room temperature. The next three adsorb as molecules in the adjacent region. Three more water molecules rearrange this structure and an additional nine pile up above the OH groups. Despite offering undercoordinated In and O sites, the rest of the unit cell is unfavorable for adsorption and remains water-free. The first water layer thus shows ordering into nanoscopic 3D water clusters separated by hydrophobic pockets

Who with whom: functional coordination of E2 enzymes by RING E3 ligases during poly-ubiquitylation

Protein modification with poly-ubiquitin chains is a crucial process involved in a myriad of cellular pathways. Chain synthesis requires two steps: substrate modification with ubiquitin (priming) followed by repetitive ubiquitin-to-ubiquitin attachment (elongation). RING-type E3 ligases catalyze both reactions in collaboration with specific priming and elongating E2 enzymes. We provide kinetic insight into poly-ubiquitylation during protein quality control by showing that priming is the rate-determining step in protein degradation as directed by the yeast ERAD RING E3 ligases, Hrd1 and Doa10. Doa10 cooperates with the dedicated priming E2, Ubc6, while both E3s use Ubc7 for elongation. Here, we provide direct evidence that Hrd1 uses Ubc7 also for priming. We found that Ubc6 has an unusually high basal activity that does not require strong stimulation from an E3. Doa10 exploits this property to pair with Ubc6 over Ubc7 during priming. Our work not only illuminates the mechanisms of specific E2/E3 interplay in ERAD, but also offers a basis to understand how RING E3s may have properties that are tailored to pair with their preferred E2s

FuLeeca: A Lee-based Signature Scheme

In this work we introduce a new code-based signature scheme, called \textsf{FuLeeca}, based on the NP-hard problem of finding codewords of given Lee-weight. The scheme follows the Hash-and-Sign approach applied to quasi-cyclic codes. Similar approaches in the Hamming metric have suffered statistical attacks, which revealed the small support of the secret basis. Using the Lee metric, we are able to thwart such attacks. We use existing hardness results on the underlying problem and study adapted statistical attacks. We propose parameters for \textsf{FuLeeca}~and compare them to an extensive list of proposed post-quantum secure signature schemes including the ones already standardized by NIST. This comparison reveals that \textsf{FuLeeca}~is competitive. For example, for NIST category I, i.e., 160 bit of classical security, we obtain an average signature size of 1100 bytes and public key sizes of 1318 bytes. Comparing the total communication cost, i.e., the sum of the signature and public key size, we see that \textsf{FuLeeca} is only outperformed by Falcon while the other standardized schemes Dilithium and SPHINCS+ show larger communication costs than \textsf{FuLeeca}

Pore timing:the evolutionary origins of the nucleus and nuclear pore complex

The name “eukaryote” is derived from Greek, meaning “true kernel”, and describes the domain of organisms whose cells have a nucleus. The nucleus is thus the defining feature of eukaryotes and distinguishes them from prokaryotes (Archaea and Bacteria), whose cells lack nuclei. Despite this, we discuss the intriguing possibility that organisms on the path from the first eukaryotic common ancestor to the last common ancestor of all eukaryotes did not possess a nucleus at all—at least not in a form we would recognize today—and that the nucleus in fact arrived relatively late in the evolution of eukaryotes. The clues to this alternative evolutionary path lie, most of all, in recent discoveries concerning the structure of the nuclear pore complex. We discuss the evidence for such a possibility and how this impacts our views of eukaryote origins and how eukaryotes have diversified subsequent to their last common ancestor

Targeting Primitive Chronic Myeloid Leukemia Cells by Effective Inhibition of a New AHI-1BCR-ABL-JAK2 Complex

This is a pre-copyedited, author-produced version of an article accepted for publication in JNCI: Journal of the National Cancer Institute following peer review. The version of record Chen, M., et al. (2013). "Targeting Primitive Chronic Myeloid Leukemia Cells by Effective Inhibition of a New AHI-1–BCR-ABL–JAK2 Complex." JNCI: Journal of the National Cancer Institute 105(6): 405-423. is available online at: https://doi.org/10.1093/jnci/djt006This work was funded by the Canadian Cancer Society (grant 700289), in part by the Canadian Institutes of Health Research, the Leukemia & Lymphoma Society of Canada, and the Cancer Research Society (XJ), the Canadian Cancer Society Research Institute (AE, XJ, CE), Cancer Research UK Programme grant C11074/A11008 (TLH), the Glasgow Experimental Cancer Medicine Centre, which is funded by Cancer Research UK and by the Chief Scientist’s Office (Scotland), and Cancer Research UK grant C973/A9894 (JP, JS). M. Chen was supported by a fellowship from Lymphoma Foundation Canada, and P. Gallipoli was supported by Medical Research Council grant G1000288. X. Jiang was a Michael Smith Foundation for Health Research Scholar

Mitochondrial Function and Dysfunction in Dilated Cardiomyopathy

Cardiac tissue requires a persistent production of energy in order to exert its pumping function. Therefore, the maintenance of this function relies on mitochondria that represent the "powerhouse" of all cardiac activities. Mitochondria being one of the key players for the proper functioning of the mammalian heart suggests continual regulation and organization. Mitochondria adapt to cellular energy demands via fusion-fission events and, as a proof-reading ability, undergo mitophagy in cases of abnormalities. Ca2+ fluxes play a pivotal role in regulating all mitochondrial functions, including ATP production, metabolism, oxidative stress balance and apoptosis. Communication between mitochondria and others organelles, especially the sarcoplasmic reticulum is required for optimal function. Consequently, abnormal mitochondrial activity results in decreased energy production leading to pathological conditions. In this review, we will describe how mitochondrial function or dysfunction impacts cardiac activities and the development of dilated cardiomyopathy