The specialization and structure of antagonistic and mutualistic networks of beetles on rainforest canopy trees

Different kinds of species interactions can lead to different structures within ecological networks. Antagonistic interactions (such as between herbivores and host plants) often promote increasing host specificity within a compartmentalized network structure, whereas mutualistic networks (such as pollination networks) are associated with higher levels of generalization and form nested network structures. However, we recently showed that the host specificity of flower‐visiting beetles from three different feeding guilds (herbivores, fungivores, and predators) in an Australian rainforest canopy was equal to that of herbivores on leaves, suggesting that antagonistic herbivores on leaves are no more specialized than flower‐visitors. We therefore set out to test whether similarities in the host specificity of these different assemblages reflect similarities in underlying network structures. As shown before at the species level, mutualistic communities on flowers showed levels of specialization at the network scale similar to those of the antagonistic herbivore community on leaves. However, the network structure differed, with flower‐visiting assemblages displaying a significantly more nested structure than folivores, and folivores displaying a significantly more compartmentalized structure than flower‐visitors. These results, which need further testing in other forest systems, demonstrate that both antagonistic and mutualistic interactions can result in equally high levels of host specialization among beetle assemblages in tropical rainforests. If this is a widespread phenomenon, it may alter our current perceptions of food web dynamics, species diversity patterns, and co‐evolution in tropical rainforests. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 287–295.     

Lrig1 is an estrogen-regulated growth suppressor and correlates with longer relapse-free survival in ERα-positive breast cancer

Lrig1 is the founding member of the Lrig family and has been implicated in the negative regulation of several oncogenic receptor tyrosine kinases including ErbB2. Lrig1 is expressed at low levels in several cancer types but is overexpressed in some prostate and colorectal tumors. Given this heterogeneity, whether Lrig1 functions to suppress or promote tumor growth remains a critical question. Previously, we found that Lrig1 was poorly expressed in ErbB2-positive breast cancer, suggesting that Lrig1 has a growth-inhibitory role in this tumor type. However, breast cancer is a complex disease, with ErbB2-positive tumors accounting for just 25% of all breast cancers. To gain a better understanding of the role of Lrig1 in breast cancer, we examined its expression in estrogen receptor α (ERα)-positive disease which accounts for the majority of breast cancers. We find that Lrig1 is expressed at significantly higher levels in ERα-positive disease than in ERα-negative disease. Our study provides a molecular rationale for Lrig1 enrichment in ERα-positive disease by showing that Lrig1 is a target of ERα. Estrogen stimulates Lrig1 accumulation and disruption of this induction enhances estrogen-dependent tumor cell growth, suggesting that Lrig1 functions as an estrogen-regulated growth suppressor. In addition, we find that Lrig1 expression correlates with prolonged relapse-free survival in ERα-positive breast cancer, identifying Lrig1 as a new prognostic marker in this setting. Finally, we show that ErbB2 activation antagonizes ERα-driven Lrig1 expression, providing a mechanistic explanation for Lrig1 loss in ErbB2-positive breast cancer. This work provides strong evidence for a growth-inhibitory role for Lrig1 in breast cancer.     

Mosquito and biting fly surveillance on Camp Zama Army Base,Kanagawa Prefecture,Japan

Camp Zama, Japan, and the associated military housing and depot storage areas have been occupied by the US military for over 50 years. The military base has experienced less urbanization and development during those 50 years when compared to the surrounding cities of Zama and Sagamihara. We present an annotated comparative checklist of historical records of biting flies (mosquitoes, black flies, biting midges, stable flies, and horse flies) with recent collections. Overall 24 species of biting flies have been reported from Camp Zama, with 17 of these species collected during the last 5 years. Vectors of human and veterinary pathogens were collected including Anopheles sinensis, Aedes albopictus, Culex tritaeniorhynchus, and Simulium bidentatum.     

Blood profile of proteins and steroid hormones predicts weight change after weight loss with interactions of dietary protein level and glycemic index

Background

Weight regain after weight loss is common. In the Diogenes dietary intervention study, high protein and low glycemic index (GI) diet improved weight maintenance.

Objective

To identify blood predictors for weight change after weight loss following the dietary intervention within the Diogenes study.

Design

Blood samples were collected at baseline and after 8-week low caloric diet-induced weight loss from 48 women who continued to lose weight and 48 women who regained weight during subsequent 6-month dietary intervention period with 4 diets varying in protein and GI levels. Thirty-one proteins and 3 steroid hormones were measured.

Results

Angiotensin I converting enzyme (ACE) was the most important predictor. Its greater reduction during the 8-week weight loss was related to continued weight loss during the subsequent 6 months, identified by both Logistic Regression and Random Forests analyses. The prediction power of ACE was influenced by immunoproteins, particularly fibrinogen. Leptin, luteinizing hormone and some immunoproteins showed interactions with dietary protein level, while interleukin 8 showed interaction with GI level on the prediction of weight maintenance. A predictor panel of 15 variables enabled an optimal classification by Random Forests with an error rate of 24±1%. A logistic regression model with independent variables from 9 blood analytes had a prediction accuracy of 92%.

Conclusions

A selected panel of blood proteins/steroids can predict the weight change after weight loss. ACE may play an important role in weight maintenance. The interactions of blood factors with dietary components are important for personalized dietary advice after weight loss.

Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00390637","term_id":"NCT00390637"}}NCT00390637     

The U11/U12 snRNP 65K protein acts as a molecular bridge, binding the U12 snRNA and U11-59K protein

U11 and U12 interact cooperatively with the 5' splice site and branch site of pre-mRNA as a stable preformed di-snRNP complex, thereby bridging the 5' and 3' ends of the intron within the U12-dependent prespliceosome. To identify proteins contributing to di-snRNP formation and intron bridging, we investigated protein-protein and protein-RNA interactions between components of the U11/U12 snRNP. We demonstrate that the U11/U12-65K protein possesses dual binding activity, interacting directly with U12 snRNA via its C-terminal RRM and the U11-associated 59K protein via its N-terminal half. We provide evidence that, in contrast to the previously published U12 snRNA secondary structure model, the 3' half of U12 forms an extended stem-loop with a highly conserved seven-nucleotide loop and that the latter serves as the 65K binding site. Addition of an oligonucleotide comprising the 65K binding site to an in vitro splicing reaction inhibited U12-dependent, but not U2-dependent, pre-mRNA splicing. Taken together, these data suggest that U11/U12-65K and U11-59K contribute to di-snRNP formation and intron bridging in the minor prespliceosome.     

Association of ebola virus matrix protein VP40 with microtubules

Viruses exploit a variety of cellular components to complete their life cycles, and it has become increasingly clear that use of host cell microtubules is a vital part of the infection process for many viruses. A variety of viral proteins have been identified that interact with microtubules, either directly or via a microtubule-associated motor protein. Here, we report that Ebola virus associates with microtubules via the matrix protein VP40. When transfected into mammalian cells, a fraction of VP40 colocalized with microtubule bundles and VP40 coimmunoprecipitated with tubulin. The degree of colocalization and microtubule bundling in cells was markedly intensified by truncation of the C terminus to a length of 317 amino acids. Further truncation to 308 or fewer amino acids abolished the association with microtubules. Both the full-length and the 317-amino-acid truncation mutant stabilized microtubules against depolymerization with nocodazole. Direct physical interaction between purified VP40 and tubulin proteins was demonstrated in vitro. A region of moderate homology to the tubulin binding motif of the microtubule-associated protein MAP2 was identified in VP40. Deleting this region resulted in loss of microtubule stabilization against drug-induced depolymerization. The presence of VP40-associated microtubules in cells continuously treated with nocodazole suggested that VP40 promotes tubulin polymerization. Using an in vitro polymerization assay, we demonstrated that VP40 directly enhances tubulin polymerization without any cellular mediators. These results suggest that microtubules may play an important role in the Ebola virus life cycle and potentially provide a novel target for therapeutic intervention against this highly pathogenic virus.     

A -1 frameshift in the HIV-1 env gene is enhanced by arginine deficiency via a hungry codon mechanism

Ribosomal frameshifting is used by various organisms to maximize protein coding potential of genomic sequences. It is commonly exploited by RNA viruses to overcome the constraint of their limited genome size. Frameshifting requires specific RNA structural features, such as a suitable heptanucleotide “slippery” sequence and an RNA pseudoknot. Previous genomic analysis of HIV-1 indicated the potential for several hidden genes encoded through frameshifting; one of these, overlapping the envelope gene, has an RNA pseudoknot just downstream from a slippery sequence, AAAAAGA that features an adenine quadruplet prior to a potential hungry arginine codon (AGA). This env-frameshift (env-fs) gene has been shown to encode a truncated glutathione peroxidase homologue, with both antioxidant and anti-apoptotic activities in transfected cells. Using a dual reporter cell-based frameshift assay, we demonstrate that the env-fs frameshift sequence is active in vitro. Furthermore, in arginine deficient media, env-fs frameshifting increased over 100% (p < 0.005), consistent with the hypothesized hungry codon mechanism. As a response to arginine deficiency, increased expression of the antioxidant viral GPx gene (env-fs) by upregulation of frameshifting could be protective to HIV-infected cells, as a countermeasure to the increased oxidative stress induced by arginine deficiency (because NO is a known scavenger of hydroxyl radical).