Hsp70/Hsc70 regulates the effect phosphorylation has on stabilizing ataxin-1

Spinocerebellar ataxia type 1 (SCA1) is an inherited neurodegenerative disorder. The mutation causing SCA1 is an expansion in the polyglutamine tract of the ATXN1 protein. Previous work demonstrated that phosphorylation of mutant ATXN1 at serine 776 (S776), a putative Akt phosphorylation site, is critical for pathogenesis. To examine this pathway further, we utilized a cell-transfection system that allowed the targeting of Akt to either the cytoplasm or the nucleus. In contrast to HeLa cells, we found that Akt targeted to the cytoplasm increased the degradation of ATXN1 in Chinese hamster ovary cells. However, Akt targeted to the cytoplasm failed to destabilize ATXN1 if Hsp70/Hsc70 was present. Thus, Hsp70/Hsc70 can regulate ATXN1 levels in concert with phosphorylation of ATXN1 at S776.     

Glutamate production by HIV-1 infected human macrophage is blocked by the inhibition of glutaminase

Mononuclear phagocyte (macrophages and microglia) dysfunction plays a significant role in the pathogenesis of human immunodeficiency virus (HIV) associated dementia (HAD) through the production and release of soluble neurotoxic factors including glutamate. The mechanism of glutamate regulation by HIV-1 infection remains unclear. In this report, we investigated whether the enzyme glutaminase is responsible for glutamate generation by HIV-1 infected monocyte-derived macrophages. We tested the functionality of novel small molecule inhibitors designed to specifically block the activity of glutaminase. Glutaminase inhibitors were first characterized in a kinetic assay with crude glutaminase from rat brain revealing an uncompetitive mechanism of inhibition. The inhibitors were then tested in vitro for their ability to prevent glutamate generation by HIV-infected macrophages, their effect upon macrophage viability, and HIV infection. To validate these findings, glutaminase specific siRNA was tested for its ability to prevent glutamate increase during infection. Our results show that both glutaminase specific small molecule inhibitors and glutaminase specific siRNA were effective at preventing increases in glutamate by HIV-1 infected macrophage. These findings support glutaminase as a potential component of the HAD pathogenic process and identify a possible therapeutic avenue for the treatment of neuroinflammatory states such as HAD.     

Hereditary evaluation of multiple developmental abnormalities in the Havanese dog breed

The Havanese is a toy breed that presents with a wide range of developmental abnormalities. Skeletal defects, particularly osteochondrodysplasia (OCD), are the most frequently observed anomalies. Cataracts, liver shunts, heart murmurs, and missing incisors are also common in this breed. Estimates of heritability and complex segregation analyses were carried out to evaluate modes of transmission for these abnormalities. A moderate heritability was identified and evidence for a single major locus was found. Novel statistical analysis methods were used to identify four traits that co-segregate: cataracts, hepatic abnormalities, OCD, and cardiac abnormalities. A canine-specific microarray was used to identify changes in gene expression in the liver that accompany the aforementioned developmental problems. One hundred and thirteen genes were found to be differentially regulated in the Havanese.     

Biophysical analysis of the EPEC translocated intimin receptor-binding domain

Enteropathogenic Escherichia coli (EPEC) are Gram (-) bacteria responsible for widespread illness in the form of diarrhea. EPEC cells attach to the intestinal epithelium using a Type III secretion system common to many Gram (-) bacteria. The translocated intimin receptor (TIR) is the first protein secreted through the EPEC secretion complex, and is absolutely required for pathogenesis. It inserts into the intestinal epithelium, serving as an anchor responsible for the attachment of EPEC to the host epithelial cell. Intimin is a transmembrane protein displayed on the EPEC cell surface with an extracellular domain that binds TIR. Observation of a TIR-TIR dimer in the X-ray co-crystal structure of the extracellular domains of intimin and TIR raised the question of how these protein domains interact and function in solution. Herein we report that the extracellular domain of TIR exists in a folded and active monomeric state in solution, as confirmed by analytical ultracentrifugation, analytical size-exclusion HPLC, isothermal titration calorimetry, and surface plasmon resonance.     

Cation control of dimensionality in isothiocyanate coordination polymers constructed from conformationally flexible 3,3′-bipyridine tethers

Two isothiocyanate coordination polymers constructed from the conformationally flexible tethering ligand 3,3′-bipyridine (3,3′-bpy) and divalent metal cations have been prepared and characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental analysis. [Co(NCS)₂(3,3′-bpy)₂] (1), wherein the isothiocyanate ligands are coordinated in a trans fashion, manifests stacked two-dimensional (2-D) rhomboid grid layered motifs. In contrast, [Ni(NCS)₂(3,3′-bpy)₂] (2) possesses a doubly interpenetrated adamantoid three-dimensional (3-D) network despite the presence of trans isothiocyanate ligands. Thus, a metal cation-based control of coordination polymer dimensionality has been revealed in this system, reflective of different donor dispositions allowed by the conformational flexibility of the exobidentate 3,3′-bpy ligand. The 3-D framework of 2 decomposes at a temperature ∼40 °C higher than the 2-D network of 1.     

Colour vision and visual ecology of the blue-spotted maskray, <Emphasis Type="Italic">Dasyatis kuhlii</Emphasis> Müller &; Henle, 1814

Relatively little is known about the physical structure and ecological adaptations of elasmobranch sensory systems. In particular, elasmobranch vision has been poorly studied compared to the other senses. Virtually nothing is known about whether elasmobranchs possess multiple cone types, and therefore the potential for colour vision, or how the spectral tuning of their visual pigments is adapted to their different lifestyles. In this study, we measured the spectral absorption of the rod and cone visual pigments of the blue-spotted maskray, Dasyatis kuhlii, using microspectrophotometry. D. kuhlii possesses a rod visual pigment with a wavelength of maximum absorbance (λ_max) at 497 nm and three spectrally distinct cone types with λ_max values at 476, 498 and 552 nm. Measurements of the spectral transmittance of the ocular media reveal that wavelengths below 380 nm do not reach the retina, indicating that D. kuhlii is relatively insensitive to ultraviolet radiation. Topographic analysis of retinal ganglion cell distribution reveals an area of increased neuronal density in the dorsal retina. Based on peak cell densities and using measurements of lens focal length made using laser ray tracing and sections of frozen eyes, the estimated spatial resolving power of D. kuhlii is 4.10 cycles per degree.     

Postconflict third-party affiliation in rooks, Corvus frugilegus

Conflict features in the lives of many animal species and induces social stress mediated by glucocorticoid hormones [1]. Postconflict affiliation, between former opponents (reconciliation) or between former opponents and a bystander (third-party affiliation), has been suggested as a behavioral mechanism for reducing such stress [2], but has been studied almost exclusively in primates [3]. As with many primates, several bird species live in social groups and form affiliative relationships [4]. Do these distantly related animals also use affiliative behavior to offset the costs of conflict? We studied postconflict affiliation in a captive group of rooks. Unlike polygamous primates, monogamous rooks did not reconcile with former opponents. However, we found clear evidence of third-party affiliation after conflicts. Both initiators and targets of aggression engaged in third-party affiliation with a social partner and employed a specific behavior, bill twining, during the postconflict period. Both former aggressors and uninvolved third parties initiated affiliative contacts. Despite the long history of evolutionary divergence, the pattern of third-party affiliation in rooks is strikingly similar to that observed in tolerant primate species. Furthermore, the absence of reconciliation in rooks makes sense in light of the species differences in social systems.     

Characterization of the binding surface of the translocated intimin receptor, an essential protein for EPEC and EHEC cell adhesion

The translocated intimin receptor (TIR) of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) is required for EPEC and EHEC infections, which cause widespread illness across the globe. TIR is translocated via a type-III secretion system into the intestinal epithelial cell membrane, where it serves as an anchor for E. coli attachment via its binding partner intimin. While many aspects of EPEC and EHEC infection are now well understood, the importance of the intermolecular contacts made between intimin and TIR have not been thoroughly investigated. Herein we report site-directed mutagenesis studies on the intimin-binding domain of EPEC TIR, and how these mutations affect TIR-intimin association, as analyzed by isothermal titration calorimetry and circular dichroism. These results show how two factors govern TIR's binding to intimin: A three-residue TIR hot spot is identified that largely mediates the interaction, and mutants that alter the beta-hairpin structure of TIR severely diminish binding affinity. In addition, peptides incorporating key TIR residues identified by mutagenesis are incapable of binding intimin. These results indicate that hot spot residues and structural orientation/preorganization are required for EPEC, and likely EHEC, TIR-intimin binding.     

Cognitive adaptations of social bonding in birds

The 'social intelligence hypothesis' was originally conceived to explain how primates may have evolved their superior intellect and large brains when compared with other animals. Although some birds such as corvids may be intellectually comparable to apes, the same relationship between sociality and brain size seen in primates has not been found for birds, possibly suggesting a role for other non-social factors. But bird sociality is different from primate sociality. Most monkeys and apes form stable groups, whereas most birds are monogamous, and only form large flocks outside of the breeding season. Some birds form lifelong pair bonds and these species tend to have the largest brains relative to body size. Some of these species are known for their intellectual abilities (e.g. corvids and parrots), while others are not (e.g. geese and albatrosses). Although socio-ecological factors may explain some of the differences in brain size and intelligence between corvids/parrots and geese/albatrosses, we predict that the type and quality of the bonded relationship is also critical. Indeed, we present empirical evidence that rook and jackdaw partnerships resemble primate and dolphin alliances. Although social interactions within a pair may seem simple on the surface, we argue that cognition may play an important role in the maintenance of long-term relationships, something we name as 'relationship intelligence'.