Structure of S5a bound to monoubiquitin provides a model for polyubiquitin recognition

Ubiquitin is a key regulatory molecule in diverse cellular events. How cells determine the outcome of ubiquitylation remains unclear; however, a likely determinant is the specificity of ubiquitin receptor proteins for polyubiquitin chains of certain length and linkage. Proteasome subunit S5a contains two ubiquitin-interacting motifs (UIMs) through which it recruits ubiquitylated substrates to the proteasome for their degradation. Here, we report the structure of S5a (196-306) alone and complexed with two monoubiquitin molecules. This construct contains the two UIMs of S5a and we reveal their different ubiquitin-binding mechanisms and provide a rationale for their unique specificities for different ubiquitin-like domains. Furthermore, we provide direct evidence that S5a (196-306) binds either K63-linked or K48-linked polyubiquitin, and in both cases prefers longer chains. On the basis of these results we present a model for how S5a and other ubiquitin-binding proteins recognize polyubiquitin.     

A central role for Bid in granzyme B-induced apoptosis

Granzyme B, a protease released from cytotoxic lymphocytes, has been proposed to induce target cell death by cleaving and activating the pro-apoptotic Bcl-2 family member Bid. It has also been proposed that granzyme B can induce target cell death by activating caspases directly, by cleaving caspase substrates, and/or by cleaving several non-caspase substrates. The relative importance of Bid in granzyme B-induced cell death has therefore remained unclear. Here we report that cells isolated from various tissues of Bid-deficient mice were resistant to granzyme B-induced cell death. Consistent with the proposed role of Bid in regulating mitochondrial outer membrane permeabilization, cytochrome c remained in the mitochondria of Bid-deficient cells treated with granzyme B. Unlike wild type cells, Bid-deficient cells survived and were then able to proliferate normally, demonstrating the critical role for Bid in mediating granzyme B-induced apoptosis.     

ATR/TEM8 is highly expressed in epithelial cells lining Bacillus anthracis' three sites of entry: implications for the pathogenesis of anthrax infection

Anthrax is a disease caused by infection with spores from the bacteria Bacillus anthracis. These spores enter the body, where they germinate into bacteria and secrete a tripartite toxin that causes local edema and, in systemic infections, death. Recent studies identified the cellular receptor for anthrax toxin (ATR), a type I membrane protein. ATR is one of the splice variants of the tumor endothelial marker 8 (TEM8) gene. ATR and TEM8 are identical throughout their extracellular and transmembrane sequence, and both proteins function as receptors for the toxin. ATR/TEM8 function and expression have been associated with development of the vascular system and with tumor angiogenesis. TEM8 is selectively upregulated in endothelial cells during blood vessel formation and tumorigenesis. However, selective expression of TEM8 in endothelial cells contradicts the presumably ubiquitous expression of the receptor. To resolve this controversial issue, we evaluated the distribution of ATR/TEM8 in a variety of tissues. For this purpose, we generated and characterized a novel anti-ATR/TEM8 polyclonal antibody. Here, we show that this novel antibody recognizes all three ATR/TEM8 isoforms, which are widely and differentially expressed in various tissue types. We found that ATR/TEM8 expression is not only associated with tumor endothelial cells, as previously described. Indeed, ATR/TEM8 is highly and selectively expressed in the epithelial cells lining those organs that constitute the anthrax toxin's sites of entry, i.e., the lung, the skin, and the intestine. In fact, we show that ATR/TEM8 is highly expressed in the respiratory epithelium of the bronchi of the lung and is particularly abundant in the ciliated epithelial cells coating the bronchi. Furthermore, immunostaining of skin biopsies revealed that ATR/TEM8 is highly expressed in the keratinocytes of the epidermis. Finally, we show that the epithelial cells lining the small intestine strongly express ATR/TEM8 isoforms. This is the first demonstration that the ATR/TEM8 protein is highly expressed in epithelial cells, which represent the primary location for bacterial invasion. These results suggest that the ATR/TEM8 expression pattern that we describe here is highly relevant for understanding the pathogenesis of anthrax infection. anthrax; epithelia; lung; skin; intestine; toxin entry; receptor; bacterial pathogenesis     

Cloning and expression of the large zebrafish protocadherin gene, Fat

The cadherin superfamily members play an important role in mediating cell-cell contact and adhesion (Takeichi, M., 1991. Cadherin cell adhesion receptors as a morphogenetic regulator. Science 251, 1451-1455). A distinct subfamily, neither belonging to the classical or protocadherins includes Fat, the largest member of the cadherin super-family. Fat was originally identified in Drosophila. Subsequently, orthologues of Fat have been described in man (Dunne, J., Hanby, A. M., Poulsom, R., Jones, T. A., Sheer, D., Chin, W. G., Da, S. M., Zhao, Q., Beverley, P. C., Owen, M. J., 1995. Molecular cloning and tissue expression of FAT, the human homologue of the Drosophila fat gene that is located on chromosome 4q34-q35 and encodes a putative adhesion molecule. Genomics 30, 207-223), rat (Ponassi, M., Jacques, T. S., Ciani, L., ffrench, C. C., 1999. Expression of the rat homologue of the Drosophila fat tumour suppressor gene. Mech. Dev. 80, 207-212) and mouse (Cox, B., Hadjantonakis, A. K., Collins, J. E., Magee, A. I., 2000. Cloning and expression throughout mouse development of mfat1, a homologue of the Drosophila tumour suppressor gene fat [In Process Citation]. Dev. Dyn. 217, 233-240). In Drosophila, Fat has been shown to play an important role in both planar cell polarity and cell boundary formation during development. In this study we describe the characterization of zebrafish Fat, the first non-mammalian, vertebrate Fat homologue to be identified. The Fat protein has 64% amino acid identity and 80% similarity to human FAT and an identical domain structure to other vertebrate Fat proteins. During embryogenesis fat mRNA is expressed in the developing brain, specialised epithelial surfaces the notochord, ears, eyes and digestive tract, a pattern similar but distinct to that found in mammals.     

Host Plant Acceptance by Redlegged Earth Mite, Halotydeus destructor (Tucker) (Acarina: Penthaleidae)

Host plant acceptance behavior of redlegged earth mites (Halotydeus destructor) on cotyledons of subterranean clover (subclover) lines was investigated in the laboratory. Sustained feeding consisted of a series of short bouts of feeding; rather than one long period of feeding. H. destructor preferred to feed at mite-damaged rather than undamaged sites on cotyledons. With time the numbers of mites feeding in aggregations increased, as mites were attracted to damaged patches. Most feeding occurred in aggregations, and mites in such groups benefited by greater weight gain. The sequence of foraging leading to feeding was similar between subclover lines, however, feeding and aggregation activities were markedly reduced on a resistant line. Host plant acceptance occurred during probing but only after some feeding had occurred.     

Time to flowering of temperate pulses in vivo and generation turnover in vivo–in vitro of narrow-leaf lupin accelerated by low red to far-red ratio and high intensity in the far-red region

Understanding the role light quality plays on floral initiation is key to a range of pre-breeding tools, such as accelerated single-seed-descent. We have elucidated the effect of light quality on early flowering onset in cool-season grain legumes and developed predictive models for time to flowering under the optimised light conditions. Early and late flowering genotypes of pea, chickpea, faba bean, lentil and lupin were grown in controlled environments under different light spectra (blue and far red-enriched LED lights and metal halide). All species and genotypes showed a positive response to a decreasing red to far-red ratio (R:FR). In general, ratios above 3.5 resulted in the longest time to flowering. In environments with R:FR below 3.5, light with the highest intensity in the FR region was the most inductive. We demonstrate the importance of considering both relative (R:FR) and absolute (FR photons) light values for flower induction in grain legumes. Greater response to light spectra was observed in the later flowering genotypes, enabling a drastic compression of time to flowering between phenologically diverse genotypes. A novel protocol for robust in vitro germination of immature seeds was developed for lupin, a species known for its recalcitrance to in vitro manipulation. We show how combining this protocol with growth under conditions optimized for early flowering drastically speeds generation turnover. The improved understanding of the effect of light on flowering regulation and the development of robust in vitro culture protocols will assist the development and exploitation of biotechnological tools for legume breeding.     

Effects of heated hydrotherapy on muscle HSP70 and glucose metabolism in old and young vervet monkeys

Increasing heat shock protein 70 (HSP70) in aged and/or insulin-resistant animal models confers benefits to healthspan and lifespan. Heat application to increase core temperature induces HSPs in metabolically important tissues, and preliminary human and animal data suggest that heated hydrotherapy is an effective method to achieve increased HSPs. However, safety concerns exist, particularly in geriatric medicine where organ and cardiovascular disease commonly will preexist. We evaluated young vervet monkeys compared to old, insulin-resistant vervet monkeys (Chlorocebus aethiops sabaeus) in their core temperatures, glucose tolerance, muscle HSP70 level, and selected safety biomarkers after 10 sessions of hot water immersions administered twice weekly. Hot water immersion robustly induced the heat shock response in muscles. We observed that heat-treated old and young monkeys have significantly higher muscle HSP70 than control monkeys and treatment was without significant adverse effects on organ or cardiovascular health. Heat therapy improved pancreatic responses to glucose challenge and tended to normalize glucose excursions. A trend for worsened blood pressure and glucose values in the control monkeys and improved values in heat-treated monkeys were seen to support further investigation into the safety and efficacy of this intervention for metabolic syndrome or diabetes in young or old persons unable to exercise.     

Flawed citation practices facilitate the unsubstantiated perception of a global trend toward increased jellyfish blooms

Speculation over a global rise in jellyfish populations has become widespread in the scientific literature, but until recently the purported ‘global increase’ had not been tested. Here we present a citation analysis of peer‐reviewed literature to track the evolution of the current perception of increases in jellyfish and identify key papers involved in its establishment. Trend statements and citation threads were reviewed and arranged in a citation network. Trend statements were assessed according their degree of affirmation and spatial scale, and the appropriateness of the citations used to support statements was assessed. Analyses showed that 48.9% of publications misinterpreted the conclusions of cited sources, with a bias towards claiming jellyfish populations are increasing, with a single review having the most influence on the network. Collectively, these disparities resulted in a network based on unsubstantiated statements and citation threads. As a community, we must ensure our statements about scientific findings in general are accurately substantiated and carefully communicated such that incorrect perceptions, as in the case of jellyfish blooms, do not develop in the absence of rigorous testing.