Female differential allocation in response to extrapair offspring and social mate attractiveness

Renewed debate over what benefits females might gain from producing extra‐pair offspring emphasizes the possibility that apparent differences in quality between within‐pair and extra‐pair offspring are confounded by greater maternal investment in extra‐pair offspring. Moreover, the attractiveness of a female''s social mate can also influence contributions of both partners to a reproductive attempt. Here, we explore the complexities involved in parental investment decisions in response to extra‐pair offspring and mate attractiveness with a focus on the female point of view. Adult zebra finches paired and reproduced in a colony setting. A male''s early‐life diet quality and his extra‐pair reproductive success were used as metrics of his mating attractiveness. Females paired with males that achieved extra‐pair success laid heavier eggs than other females and spent less time attending their nests than their mates or other females. Extra‐pair nestlings were fed more protein‐rich hen''s egg than within‐pair nestlings. Females producing extra‐pair offspring had more surviving sons than females producing only within‐pair offspring. Collectively, results show that females differentially allocate resources in response to offspring extra‐pair status and their social mate''s attractiveness. Females may also obtain fitness benefits through the production of extra‐pair offspring.     

Effects of sediment loading on food perception and ingestion by freshwater copepods

Seasonal influx of suspended sediments to lakes is common in many aquatic systems, particularly during periods of high flow. Suspended particles not only affect visibility and net primary productivity, as light penetration is reduced, but may also affect the ability of herbivorous zooplankton to locate and ingest food. In Swan Lake, an oligotrophic lake in northwestern Montana, the dose association between zooplankton population development and seasonal maxima in turbidity levels suggests that the community present during peak turbidity is minimally impacted by suspended sediments. This report presents the results of laboratory investigations into the effect of suspended sediments on feeding by the copepod Diaptomus ashlandii, the dominant zoo‐plankter in Swan Lake. Ingestion rate for copepods feeding on ³²P labeled algae was significantly reduced in the presence of suspended particles at all turbidity levels tested (5 to 200 NTU's) compared to ingestion rate in the absence of suspended particles (0 NTU's).     

Calcitriol downregulates TNF-α and IL-6 expression in cultured placental cells from preeclamptic women

Placenta is an important source and target of hormones that contribute to immunological tolerance and maintenance of pregnancy. In preeclampsia (PE), placental calcitriol synthesis is low; whereas pro-inflammatory cytokines levels are increased, threatening pregnancy outcome. Previously, we showed that calcitriol inhibits Th-1 cytokines under experimental inflammatory conditions in normal trophoblasts. However, a study of the regulation of inflammatory cytokines by calcitriol in trophoblasts from a natural inflammatory condition, such as PE, is still lacking. Therefore, the aim of the present study was to investigate calcitriol effects upon TNF-α, IFN-γ, IL-6 and IL-1β in cultured placental cells from preeclamptic women by using qPCR and ELISA. Placentas were collected after cesarean section from preeclamptic women and enriched trophoblastic preparations were cultured in the absence or presence of different calcitriol concentrations during 24 h. In these cell cultures, pro-inflammatory cytokines TNF-α and IL-6 secretion and mRNA expression were downregulated by calcitriol (P < 0.05). No significant effects of calcitriol upon IFN-γ and IL-1β were observed. In addition, basal expression of TNF-α, IL-6 and IL-1β decreased as the cells formed syncytia. Our study supports an important autocrine/paracrine role of placental calcitriol in controlling adverse immunological responses at the feto–maternal interface, particularly in gestational pathologies associated with exacerbated inflammatory responses such as preeclampsia.     

The phosphatidylinositol‐transfer protein Nir2 binds phosphatidic acid and positively regulates phosphoinositide signalling

Phosphatidic acid (PA) and phosphoinositides are metabolically interconverted lipid second messengers that have central roles in many growth factor (GF)‐stimulated signalling pathways. Yet, little is known about the mechanisms that coordinate their production and downstream signalling. Here we show that the phosphatidylinositol (PI)‐transfer protein Nir2 translocates from the Golgi complex to the plasma membrane in response to GF stimulation. This translocation is triggered by PA formation and is mediated by its C‐terminal region that binds PA in vitro. We further show that depletion of Nir2 substantially reduces the PI(4,5)P2 levels at the plasma membrane and concomitantly GF‐stimulated PI(3,4,5)P3 production. Finally, we show that Nir2 positively regulates the MAPK and PI3K/AKT pathways. We propose that Nir2 through its PA‐binding capability and PI‐transfer activity can couple PA to phosphoinositide signalling, and possibly coordinates their local lipid metabolism and downstream signalling.     

Aging aggravates ischemic stroke‐induced brain damage in mice with chronic peripheral infection

Ischemic stroke is confounded by conditions such as atherosclerosis, diabetes, and infection, all of which alter peripheral inflammatory processes with concomitant impact on stroke outcome. The majority of the stroke patients are elderly, but the impact of interactions between aging and inflammation on stroke remains unknown. We thus investigated the influence of age on the outcome of stroke in animals predisposed to systemic chronic infection. Th1‐polarized chronic systemic infection was induced in 18–22 month and 4‐month‐old C57BL/6j mice by administration of Trichuris muris (gut parasite). One month after infection, mice underwent permanent middle cerebral artery occlusion and infarct size, brain gliosis, and brain and plasma cytokine profiles were analyzed. Chronic infection increased the infarct size in aged but not in young mice at 24 h. Aged, ischemic mice showed altered plasma and brain cytokine responses, while the lesion size correlated with plasma prestroke levels of RANTES. Moreover, the old, infected mice exhibited significantly increased neutrophil recruitment and upregulation of both plasma interleukin‐17α and tumor necrosis factor‐α levels. Neither age nor infection status alone or in combination altered the ischemia‐induced brain microgliosis. Our results show that chronic peripheral infection in aged animals renders the brain more vulnerable to ischemic insults, possibly by increasing the invasion of neutrophils and altering the inflammation status in the blood and brain. Understanding the interactions between age and infections is crucial for developing a better therapeutic regimen for ischemic stroke and when modeling it as a disease of the elderly.     

The Design and Synthesis of N 4-Anthraniloyl-2′-dC,the Improved Syntheses of N 4-Carbamoyl-and N4- Ureidocarbamoyl-2′-dC,Incorporation into Oligonucleotides and Triplex Formation Testing

Abstract

Three modified nucleosides were designed with the aim of achieving triplet formation with the CG base pair of duplex DNA. Direct anthraniloylation of 2′-deoxycytidine, using isatoic anhydride, afforded the novel N ⁴-anthraniloyl-2′-deoxycytidine. Much improved preparations of N ⁴-carbamoyl-2′-deoxycytidine and of N ⁴-ureidocarbonyl-2′-deoxycytidine were accomplished. The modified nucleosides were incorporated into oligonucleotides. Thermal denaturation studies and gel mobility shift analysis suggest that these nucleosides do not form base triplets with any of the four base pairs of DNA.     

System-wide Analysis Reveals Intrinsically Disordered Proteins Are Prone to Ubiquitylation after Misfolding Stress

Damaged and misfolded proteins that are no longer functional in the cell need to be eliminated. Failure to do so might lead to their accumulation and aggregation, a hallmark of many neurodegenerative diseases. Protein quality control pathways play a major role in the degradation of these proteins, which is mediated mainly by the ubiquitin proteasome system. Despite significant focus on identifying ubiquitin ligases involved in these pathways, along with their substrates, a systems-level understanding of these pathways has been lacking. For instance, as misfolded proteins are rapidly ubiquitylated, unconjugated ubiquitin is rapidly depleted from the cell upon misfolding stress; yet it is unknown whether certain targets compete more efficiently to be ubiquitylated. Using a system-wide approach, we applied statistical and computational methods to identify characteristics enriched among proteins that are further ubiquitylated after heat shock. We discovered that distinct populations of structured and, surprisingly, intrinsically disordered proteins are prone to ubiquitylation. Proteomic analysis revealed that abundant and highly structured proteins constitute the bulk of proteins in the low-solubility fraction after heat shock, but only a portion is ubiquitylated. In contrast, ubiquitylated, intrinsically disordered proteins are enriched in the low-solubility fraction after heat shock. These proteins have a very low abundance in the cell, are rarely encoded by essential genes, and are enriched in binding motifs. In additional experiments, we confirmed that several of the identified intrinsically disordered proteins were ubiquitylated after heat shock and demonstrated for two of them that their disordered regions are important for ubiquitylation after heat shock. We propose that intrinsically disordered regions may be recognized by the protein quality control machinery and thereby facilitate the ubiquitylation of proteins after heat shock.Cells face the constant threat of protein misfolding and aggregation, and thus protein quality control pathways are important in selectively targeting damaged and misfolded proteins for degradation (1, 2). The ubiquitin proteasome system serves as a major mediator of this pathway by conjugating the small protein ubiquitin onto substrates through the E1-E2-E3 (ubiquitin-activating enzyme, ubiquitin-conjugating enzyme, and ubiquitin ligase, respectively) cascade for their recognition and degradation by the proteasome (3, 4). It is known that the activity of the ubiquitin-proteasome system is associated with many neurodegenerative diseases. For instance, ubiquitin is found enriched in protein inclusions associated with these diseases (5). Furthermore, proteasome activity has been shown to decrease with age in a large variety of organisms (6), leading to increased proteotoxicity in the cell.Because of the importance of maintaining protein homeostasis, numerous ubiquitin ligases in different cellular compartments function in protein quality control pathways to target misfolded or damaged proteins for degradation via the proteasome. For instance, the conserved Hrd1 ubiquitin ligase is involved in the endoplasmic-reticulum-associated degradation pathway that targets endoplasmic reticulum proteins for retro-translocation to the cytoplasm and proteasome degradation (7). A major question is what features are recognized by ubiquitin ligases that allow them to selectively target terminally misfolded proteins for degradation, given that the folding rates and physicochemical properties vary largely from protein to protein. Several E3 ubiquitin ligases involved in cytosolic protein quality control target their substrates via their interactions with chaperone proteins. For instance, the CHIP ubiquitin ligase can directly bind to Hsp70 and Hsp90 proteins (8), which may hand over client proteins that are not successfully folded. Understanding which features are recognized by these degradation quality-control pathways might help us understand how certain misfolded proteins evade this system, leading to their accumulation and aggregation in the cell.Many studies investigating degradation protein quality control have employed model substrates (e.g. mutated proteins that misfold) to reveal which components are involved in a given quality control machinery. However, these approaches do not typically reveal the whole spectrum of substrates for these pathways. Thus, alternative system-wide approaches are also needed to provide a bigger picture. Heat shock (HS)¹ induces general misfolding at the proteome level by increasing thermal energy and was shown to cause an increase in ubiquitylation levels in the cell over 25 years ago (9, 10). However, the exact mechanism and pathways that target misfolded proteins have remained uncharacterized for a long time. We recently showed that the Hul5 ubiquitin ligase plays a major role in this heat stress response that mainly affects cytosolic proteins (11). Absence of Hul5 averts the ubiquitylation in the cytoplasm of several misfolded targets after HS, as well as low-solubility proteins in unstressed cells. Other E3 ubiquitin ligases are likely involved in this pathway (12). Interestingly, as ubiquitin constitutes about only 1% of the proteome, free unconjugated ubiquitin is rapidly depleted under stress conditions (13, 14). Given the limited amount of this protein, how does the cell triage ubiquitin among an excess of misfolded proteins? In order to gain systems-level insight, we sought to identify characteristics enriched among proteins ubiquitylated after HS using a combination of statistical and computational analysis, and we conducted additional proteomics and biochemical experiments to support our hypotheses. We discovered an unexpected susceptibility of intrinsically disordered proteins for ubiquitylation after misfolding stress.     

Multiparasitism of Piezodorus guildinii eggs by Telenomus podisi and Trissolcus urichi

Multiparasitism involves competition between larvae inside the host. Telenomus podisi (Ashmead) and Trissolcus urichi (Crawford) (Hymenoptera: Platygastridae) are solitary egg parasitoids of Piezodorus guildinii Westwood (Hemiptera: Pentatomidae), an important soybean pest. Egg masses partially parasitized by one species were offered to females of the other species. Both species attacked randomly unparasitized and parasitized hosts. Emergence from multiparasitized eggs was greater for T. urichi than for T. podisi, although it was lower than emergence from eggs parasitized by T. urichi alone. Emergence of each species was independent of the order in which they parasitized and of time elapsed between ovipositions. Progeny sex ratio obtained from multiparasitized and from parasitized eggs were similar for both parasitoids. Our results suggest that T. urichi is a better intrinsic competitor than T. podisi for P. guildinii eggs. In the field, however, T. podisi was the dominant species, and T. urichi could be using other pentatomid eggs as resource.