Two Mosquito LRR Proteins Function as Complement Control Factors in the TEP1-Mediated Killing of Plasmodium

SummaryPlasmodium development within Anopheles mosquitoes is a vulnerable step in the parasite transmission cycle, and targeting this step represents a promising strategy for malaria control. The thioester-containing complement-like protein TEP1 and two leucine-rich repeat (LRR) proteins, LRIM1 and APL1, have been identified as major mosquito factors that regulate parasite loads. Here, we show that LRIM1 and APL1 are required for binding of TEP1 to parasites. RNAi silencing of the LRR-encoding genes results in deposition of TEP1 on Anopheles tissues, thereby depleting TEP1 from circulation in the hemolymph and impeding its binding to Plasmodium. LRIM1 and APL1 not only stabilize circulating TEP1, they also stabilize each other prior to their interaction with TEP1. Our results indicate that three major antiparasitic factors in mosquitoes jointly function as a complement-like system in parasite killing, and they reveal a role for LRR proteins as complement control factors

Role of NF-kappaB signaling cascades in the mosquito Anopheles gambiae immune responses

Le moustique Anopheles gambiae est le vecteur principal du paludisme dont l'agent Plasmodium tue chaque année un million d'enfants.L'objet de cette thèse a été d'étudier la régulation de la réponse immunitaire de ce moustique grâce aux données fournies par le séquençage du génome de l'anophèle en 2002.Nous avons pu démontrer que les cascades de type NF-kappaB, connues pour être impliquées dans la régulation de la réponse immunitaire de l'insecte modèle drosophile,sont conservées chez l'anphèle.Nous avons mis en évidence le rôle de la cascade Rel1 dans la réponse déclenchée suite à une infection fongique,et le rôle de la cascade Rel2 dans la production des peptides antimicrobiens.Nous avons démontré le rôle des facteurs de transcription de type NF-kappaB Rel1 et Rel2 dans la régulation de la transcription basale d'un certain nombre de gènes aux propriétés antiparasitaires et nous avons établi le rôle crucial de cette expression basale lors de la défense contre l'infection par Plasmodium berghei.En effet,nous avons pu bloquer la progression de P.berghei et ainsi rendre les anophèles réfractaires à ce parasite en augmentant cette immunité basale par l'invalidation du gène codant pour le répresseur de type IkappaB,Cactus.C'est la première fois qu'un tel phénotype a pu être obtenu par l'invalidation d'un gène.L'invalidation de cactus est un outil puissant pour découvrir de nouveaux effecteurs impliqués dans la réponse immunitaire contre le Plasmodium.Anopheles gambiae is the major vector for human malaria which kills one million childrenevery year.Here we studied the regulation of immune responses of Anopheles, taking advantage of the recent2002 sequencing of its genome.We could demonstrate that NF-kappaB pathways are conserved beetween Anopheles and Drosophila where they play a central role in immune responses.Moreover,we show that NF-kappaB/Rel1 is involved in the antifungal responses and that NF-kappaB/Rel2 is responsible for the antimicrobial peptides production.We demonstrated that Rel1 and Rel2 control the basal level of expression of antiparasitic genes such as TEP1 and LRIM1.Boosting this basal level by Ikappa/Cactus silencing resulted in a complete blocage of parasite transmission,thus demontrating the crucial role of basal immunity in the defense against P.gerghei.This is the first demonstration of the role of basal immunity in antipasitic defenses and dsCactus mosquitoes now consitute a new tool to study Anopheles-Plasmodium interactions and to identify genes involved in parasite killing

Role of NF-kappaB signaling cascades in the mosquito Anopheles gambiae immune responses

Le moustique Anopheles gambiae est le vecteur principal du paludisme dont l'agent Plasmodium tue chaque année un million d'enfants.L'objet de cette thèse a été d'étudier la régulation de la réponse immunitaire de ce moustique grâce aux données fournies paAnopheles gambiae is the major vector for human malaria which kills one million childrenevery year.Here we studied the regulation of immune responses of Anopheles, taking advantage of the recent2002 sequencing of its genome.We could demonstrate that NF-k

Rôle des voies de signalisation de type IkappaB/NF-kappaB dans la réponse immunitaire du moustique Anopheles gambiae

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Rôle des voies de signalisation de type IkappaB/NF-kappaB dans la réponse immunitaire du moustique Anopheles gambiae

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Streptococcus pneumoniae Choline-Binding Protein E Interaction with Plasminogen/Plasmin Stimulates Migration across the Extracellular Matrix▿

The virulence mechanisms leading Streptococcus pneumoniae to convert from nasopharyngeal colonization to a tissue-invasive phenotype are still largely unknown. Proliferation of infection requires penetration of the extracellular matrix, which occurs by recruitment of host proteases to the bacterial cell surface. We present evidence supporting the role of choline-binding protein E (CBPE) (a member of the surface-exposed choline-binding protein family) as an important receptor for human plasminogen, the precursor of plasmin. The results of ligand overlay blot analyses, solid-phase binding assays, and surface plasmon resonance experiments support the idea of an interaction between CBPE and plasminogen. We have shown that the phosphorylcholine esterase (Pce) domain of CBPE interacts with the plasminogen kringle domains. Analysis of the crystal structure of the Pce domain, followed by site-directed mutagenesis, allowed the identification of the plasminogen-binding region composed in part by lysine residues, some of which map in a linear fashion on the surface of the Pce domain. The biological relevance of the CBPE-plasminogen interaction is supported by the fact that, compared to the wild-type strain, a mutant of pneumococcus with the cbpE gene deleted (i) displays a reduced level of plasminogen binding and plasmin activation and (ii) shows reduced ability to cross the extracellular matrix in an in vitro model. These results support the idea of a physiological role for the CBPE-plasminogen interaction in pneumococcal dissemination into human tissue

New adhesin functions of surface-exposed pneumococcal proteins

Abstract Background Streptococcus pneumoniae is a widely distributed commensal Gram-positive bacteria of the upper respiratory tract. Pneumococcal colonization can progress to invasive disease, and thus become lethal, reason why antibiotics and vaccines are designed to limit the dramatic effects of the bacteria in such cases. As a consequence, pneumococcus has developed efficient antibiotic resistance, and the use of vaccines covering a limited number of serotypes such as Pneumovax® and Prevnar® results in the expansion of non-covered serotypes. Pneumococcal surface proteins represent challenging candidates for the development of new therapeutic targets against the bacteria. Despite the number of described virulence factors, we believe that the majority of them remain to be characterized. This is the reason why pneumococcus invasion processes are still largely unknown. Results Availability of genome sequences facilitated the identification of pneumococcal surface proteins bearing characteristic motifs such as choline-binding proteins (Cbp) and peptidoglycan binding (LPXTG) proteins. We designed a medium throughput approach to systematically test for interactions between these pneumococcal surface proteins and host proteins (extracellular matrix proteins, circulating proteins or immunity related proteins). We cloned, expressed and purified 28 pneumococcal surface proteins. Interactions were tested in a solid phase assay, which led to the identification of 23 protein-protein interactions among which 20 are new. Conclusions We conclude that whether peptidoglycan binding proteins do not appear to be major adhesins, most of the choline-binding proteins interact with host proteins (elastin and C reactive proteins are the major Cbp partners). These newly identified interactions open the way to a better understanding of host-pneumococcal interactions.</p