Structure of the specificity domain of the Dorsal homologue Gambif1 bound to DNA

Background: NF-κB/Rel transcription factors play important roles in immunity and development in mammals and insects. Their activity is regulated by their cellular localization, homo- and heterodimerization and association with other factors on their target gene promoters. Gambif1 fromAnopheles gambiae is a member of the Rel family and a close homologue of the morphogen Dorsal, which establishes dorsoventral polarity in theDrosophila embryo.Results: We present the crystal structure of the N-terminal specificity domain of Gambif1 bound to DNA. This first structure of an insect Rel protein–DNA complex shows that Gambif1 binds a GGG half-site element using a stack of three arginine sidechains. Differences in affinity to Dorsal binding sites in target gene promoters are predicted to arise from base changes in these GGG elements. An arginine that is conserved in class II Rel proteins (members of which contain a transcription activation domain) contacts the outermost guanines of the DNA site. This previously unseen specific contact contributes strongly to the DNA-binding affinity and might be responsible for differences in specificity between Rel proteins of class I and II.Conclusions: The Gambif1–DNA complex structure illustrates how differences in Dorsal affinity to binding sites in developmental gene promoters are achieved. Comparison with other Rel–DNA complex structures leads to a general model for DNA recognition by Rel proteins

Shorter Exposures to Harder X-Rays Trigger Early Apoptotic Events in Xenopus laevis Embryos

A long-standing conventional view of radiation-induced apoptosis is that increased exposure results in augmented apoptosis in a biological system, with a threshold below which radiation doses do not cause any significant increase in cell death. The consequences of this belief impact the extent to which malignant diseases and non-malignant conditions are therapeutically treated and how radiation is used in combination with other therapies. Our research challenges the current dogma of dose-dependent induction of apoptosis and establishes a new parallel paradigm to the photoelectric effect in biological systems. embryo. Three different experimental scenarios were analyzed and morphological and biochemical hallmarks of apoptosis were evaluated. Initially, we examined cell death events in embryos exposed to increasing incident energies when the exposure time was preset. Then, we evaluated the embryo's response when the exposure time was augmented while the energy value remained constant. Lastly, we studied the incidence of apoptosis in embryos exposed to an equal total dose of radiation that resulted from increasing the incoming energy while lowering the exposure time. absorbed dose of radiation, the response is significantly increased when shorter bursts of more energetic photons are used. These results suggest that biological organisms display properties similar to the photoelectric effect in physical systems and provide new insights into how radiation-mediated apoptosis should be understood and utilized for therapeutic purposes

Malaria Immunity in Man and Mosquito: Insights Into Unsolved Mysteries of a Deadly Infectious Disease

Malaria is a mosquito-borne disease caused by parasites of the obligate intracellular Apicomplexa family, the most deadly of which, Plasmodium falciparum, prevails in Africa. Malaria imposes a huge health burden on the world’s most vulnerable populations, claiming the lives of nearly a million children and pregnant women each year in Africa alone. Although there is keen interest in eradicating malaria, we do not yet have the necessary tools to meet this challenge, including an effective malaria vaccine and adequate vector control strategies. Here we review what is known about the mechanisms at play in immune resistance to malaria in both the human and mosquito hosts at each step in the parasite’s complex life cycle with a view towards developing the tools that will contribute to the prevention of disease and death and ultimately the goal of malaria eradication. In so doing we hope to inspire immunologists to participate in defeating this devastating disease

Prooxidant/Antioxidant Balance in Hypoxia: A Cross-Over Study on Normobaric vs. Hypobaric “Live High-Train Low”

“Live High-Train Low” (LHTL) training can alter oxidative status of athletes. This study compared prooxidant/antioxidant balance responses following two LHTL protocols of the same duration and at the same living altitude of 2250 m in either normobaric (NH) or hypobaric (HH) hypoxia. Twenty-four well-trained triathletes underwent the following two 18-day LHTL protocols in a cross-over and randomized manner: Living altitude (PIO2 = 111.9 ± 0.6 vs. 111.6 ± 0.6 mmHg in NH and HH, respectively); training “natural” altitude (~1000–1100 m) and training loads were precisely matched between both LHTL protocols. Plasma levels of oxidative stress [advanced oxidation protein products (AOPP) and nitrotyrosine] and antioxidant markers [ferric-reducing antioxidant power (FRAP), superoxide dismutase (SOD) and catalase], NO metabolism end-products (NOx) and uric acid (UA) were determined before (Pre) and after (Post) the LHTL. Cumulative hypoxic exposure was lower during the NH (229 ± 6 hrs.) compared to the HH (310 ± 4 hrs.; P<0.01) protocol. Following the LHTL, the concentration of AOPP decreased (-27%; P<0.01) and nitrotyrosine increased (+67%; P<0.05) in HH only. FRAP was decreased (-27%; P<0.05) after the NH while was SOD and UA were only increased following the HH (SOD: +54%; P<0.01 and UA: +15%; P<0.01). Catalase activity was increased in the NH only (+20%; P<0.05). These data suggest that 18-days of LHTL performed in either NH or HH differentially affect oxidative status of athletes. Higher oxidative stress levels following the HH LHTL might be explained by the higher overall hypoxic dose and different physiological responses between the NH and HH.The study was funded by grants from the Ministère des Sports, de la Jeunesse, de l’Education Populaire et de la Vie Associative (MSJEPVA; France; to L.S. and G.P.M.), Institut National du Sport, de l’Expertise et de la Performance (INSEP; France; to L.S. and G.P.M.) and Institut Universitaire de France (IUF; France; to V.P.)

The JAK-STAT Pathway Controls Plasmodium vivax Load in Early Stages of Anopheles aquasalis Infection

Malaria affects 300 million people worldwide every year and 450,000 in Brazil. In coastal areas of Brazil, the main malaria vector is Anopheles aquasalis, and Plasmodium vivax is responsible for the majority of malaria cases in the Americas. Insects possess a powerful immune system to combat infections. Three pathways control the insect immune response: Toll, IMD, and JAK-STAT. Here we analyze the immune role of the A. aquasalis JAK-STAT pathway after P. vivax infection. Three genes, the transcription factor Signal Transducers and Activators of Transcription (STAT), the regulatory Protein Inhibitors of Activated STAT (PIAS) and the Nitric Oxide Synthase enzyme (NOS) were characterized. Expression of STAT and PIAS was higher in males than females and in eggs and first instar larvae when compared to larvae and pupae. RNA levels for STAT and PIAS increased 24 and 36 hours (h) after P. vivax challenge. NOS transcription increased 36 h post infection (hpi) while this protein was already detected in some midgut epithelial cells 24 hpi. Imunocytochemistry experiments using specific antibodies showed that in non-infected insects STAT and PIAS were found mostly in the fat body, while in infected mosquitoes the proteins were found in other body tissues. The knockdown of STAT by RNAi increased the number of oocysts in the midgut of A. aquasalis. This is the first clear evidence for the involvement of a specific immune pathway in the interaction of the Brazilian malaria vector A. aquasalis with P. vivax, delineating a potential target for the future development of disease controlling strategies

An Epithelial Serine Protease, AgESP, Is Required for Plasmodium Invasion in the Mosquito Anopheles gambiae

Background: Plasmodium parasites need to cross the midgut and salivary gland epithelia to complete their life cycle in the mosquito. However, our understanding of the molecular mechanism and the mosquito genes that participate in this process is still very limited. Methodology/Principal Findings: We identified an Anopheles gambiae epithelial serine protease (AgESP) that is constitutively expressed in the submicrovillar region of mosquito midgut epithelial cells and in the basal side of the salivary glands that is critical for Plasmodium parasites to cross these two epithelial barriers. AgESP silencing greatly reduces Plasmodium berghei and Plasmodium falciparum midgut invasion and prevents the transcriptional activation of gelsolin, a key regulator of actin remodeling and a reported Plasmodium agonist. AgESP expression is highly induced in midgut cells invaded by Plasmodium, suggesting that this protease also participates in the apoptotic response to invasion. In salivary gland epithelial cells, AgESP is localized on the basal side–the surface with which sporozoites interact. AgESP expression in the salivary gland is also induced in response to P. berghei and P. falciparum sporozoite invasion, and AgESP silencing significantly reduces the number of sporozoites that invade this organ. Conclusion: Our findings indicate that AgESP is required for Plasmodium parasites to effectively traverse the midgut and salivary gland epithelial barriers. Plasmodium parasites need to modify the actin cytoskeleton of mosquito epithelial cells t

Proteases of haematophagous arthropod vectors are involved in blood-feeding, yolk formation and immunity : a review

Ticks, triatomines, mosquitoes and sand flies comprise a large number of haematophagous arthropods considered vectors of human infectious diseases. While consuming blood to obtain the nutrients necessary to carry on life functions, these insects can transmit pathogenic microorganisms to the vertebrate host. Among the molecules related to the blood-feeding habit, proteases play an essential role. In this review, we provide a panorama of proteases from arthropod vectors involved in haematophagy, in digestion, in egg development and in immunity. As these molecules act in central biological processes, proteases from haematophagous vectors of infectious diseases may influence vector competence to transmit pathogens to their prey, and thus could be valuable targets for vectorial control

Gene expression patterns associated with blood-feeding in the malaria mosquito Anopheles gambiae

BACKGROUND: Blood feeding, or hematophagy, is a behavior exhibited by female mosquitoes required both for reproduction and for transmission of pathogens. We determined the expression patterns of 3,068 ESTs, representing ~2,000 unique gene transcripts using cDNA microarrays in adult female Anopheles gambiae at selected times during the first two days following blood ingestion, at 5 and 30 min during a 40 minute blood meal and at 0, 1, 3, 5, 12, 16, 24 and 48 hours after completion of the blood meal and compared their expression to transcript levels in mosquitoes with access only to a sugar solution. RESULTS: In blood-fed mosquitoes, 413 unique transcripts, approximately 25% of the total, were expressed at least two-fold above or below their levels in the sugar-fed mosquitoes, at one or more time points. These differentially expressed gene products were clustered using k-means clustering into Early Genes, Middle Genes, and Late Genes, containing 144, 130, and 139 unique transcripts, respectively. Several genes from each group were analyzed by quantitative real-time PCR in order to validate the microarray results. CONCLUSION: The expression patterns and annotation of the genes in these three groups (Early, Middle, and Late genes) are discussed in the context of female mosquitoes' physiological responses to blood feeding, including blood digestion, peritrophic matrix formation, egg development, and immunity