The AMA1-RON complex drives Plasmodium sporozoite invasion in the mosquito and mammalian hosts

Plasmodium sporozoites that are transmitted by blood-feeding female Anopheles mosquitoes invade hepatocytes for an initial round of intracellular replication, leading to the release of merozoites that invade and multiply within red blood cells. Sporozoites and merozoites share a number of proteins that are expressed by both stages, including the Apical Membrane Antigen 1 (AMA1) and the Rhoptry Neck Proteins (RONs). Although AMA1 and RONs are essential for merozoite invasion of erythrocytes during asexual blood stage replication of the parasite, their function in sporozoites was still unclear. Here we show that AMA1 interacts with RONs in mature sporozoites. By using DiCre-mediated conditional gene deletion in P. berghei, we demonstrate that loss of AMA1, RON2 or RON4 in sporozoites impairs colonization of the mosquito salivary glands and invasion of mammalian hepatocytes, without affecting transcellular parasite migration. Three-dimensional electron microscopy data showed that sporozoites enter salivary gland cells through a ring-like structure and by forming a transient vacuole. The absence of a functional AMA1-RON complex led to an altered morphology of the entry junction, associated with epithelial cell damage. Our data establish that AMA1 and RONs facilitate host cell invasion across Plasmodium invasive stages, and suggest that sporozoites use the AMA1-RON complex to efficiently and safely enter the mosquito salivary glands to ensure successful parasite transmission. These results open up the possibility of targeting the AMA1-RON complex for transmission-blocking antimalarial strategies.     

Fragile X related protein 1 isoforms differentially modulate the affinity of fragile X mental retardation protein for G-quartet RNA structure

Fragile X syndrome, the most frequent form of inherited mental retardation, is due to the absence of expression of the Fragile X Mental Retardation Protein (FMRP), an RNA binding protein with high specificity for G-quartet RNA structure. FMRP is involved in several steps of mRNA metabolism: nucleocytoplasmic trafficking, translational control and transport along dendrites in neurons. Fragile X Related Protein 1 (FXR1P), a homologue and interactor of FMRP, has been postulated to have a function similar to FMRP, leading to the hypothesis that it can compensate for the absence of FMRP in Fragile X patients. Here we analyze the ability of three isoforms of FXR1P, expressed in different tissues, to bind G-quartet RNA structure specifically. Only the longest FXR1P isoform was found to be able to bind specifically the G-quartet RNA, albeit with a lower affinity as compared to FMRP, whereas the other two isoforms negatively regulate the affinity of FMRP for G-quartet RNA. This result is important to decipher the molecular basis of fragile X syndrome, through the understanding of FMRP action in the context of its multimolecular complex in different tissues. In addition, we show that the action of FXR1P is synergistic rather than compensatory for FMRP function.     

Jelly-falls historic and recent observations: a review to drive future research directions

The biological pump describes the transport of particulate matter from the sea surface to the ocean’s interior including the seabed. The contribution by gelatinous zooplankton bodies as particulate organic matter (POM) vectors (“jelly-falls”) has been neglected owing to technical and spatiotemporal sampling limitations. Here, we assess the existing evidence on jelly-falls from early ocean observations to present times. The seasonality of jelly-falls indicates that they mostly occur after periods of strong upwelling and/or spring blooms in temperate/subpolar zones and during late spring/early summer. A conceptual model helps to define a jelly-fall based on empirical and field observations of biogeochemical and ecological processes. We then compile and discuss existing strategic and observational oceanographic techniques that could be implemented to further jelly-falls research. Seabed video- and photography-based studies deliver the best results, and the correct use of fishing techniques, such as trawling, could provide comprehensive regional datasets. We conclude by considering the possibility of increased gelatinous biomasses in the future ocean induced by upper ocean processes favouring their populations, thus increasing jelly-POM downward transport. We suggest that this could provide a “natural compensation” for predicted losses in pelagic POM with respect to fuelling benthic ecosystems.     

Pituitary stalk interruption syndrome: diagnostic delay and sensitivity of the auxological criteria of the growth hormone research society

Objectives

To study the diagnostic delay for pituitary stalk interruption syndrome (PSIS) with growth hormone deficiency (GHD) and the sensitivity of the auxological criteria of the Growth Hormone Research Society (GHRS) consensus guidelines.

Methods

A single-center retrospective case-cohort study covering records from January 2000 through December 2007 evaluated the performance of each GHRS auxological criterion for patients with GHD and PSIS. Diagnostic delay was calculated as the difference between the age at which the earliest GHRS criterion could have been observed and the age at diagnosis of PSIS with GHD. A diagnostic delay exceeding one year was defined as late diagnosis.

Results

The study included 21 patients, 16 (76%) of whom had isolated GHD and 5 (24%) multiple pituitary hormone deficiencies. The median age at diagnosis was 3.6 years (interquartile range, IQR, 2.6–5.5). The median diagnostic delay was 2.3 years (range 0–12.6; IQR 1.5–3.6), with late diagnosis for 17 patients (81%). Height more than 1.5 SDS below target height was the most effective criterion: 90% of the patients met the criterion before diagnosis at a median age of 1 year, and it was the first criterion to be fulfilled for 84%.

Conclusion

In our cohort, the delay for diagnosis of PSIS with GHD was long and could have been reduced by using the GHRS criteria, in particular, height more than 1.5 SDS below the target height. The specificity of such a strategy needs to be tested in healthy populations.     

Cyclooxygenases and lipoxygenases are used by the fungus Podospora anserina to repel nematodes

Oxylipins are secondary messengers used universally in the living world for communication and defense. The paradigm is that they are produced enzymatically for the eicosanoids and non-enzymatically for the isoprostanoids. They are supposed to be degraded into volatile organic compounds (VOCs) and to participate in aroma production. Some such chemicals composed of eight carbons are also envisoned as alternatives to fossil fuels. In fungi, oxylipins have been mostly studied in Aspergilli and shown to be involved in signalling asexual versus sexual development, mycotoxin production and interaction with the host for pathogenic species. Through targeted gene deletions of genes encoding oxylipin-producing enzymes and chemical analysis of oxylipins and volatile organic compounds, we show that in the distantly-related ascomycete Podospora anserina, isoprostanoids are likely produced enzymatically. We show the disappearance in the mutants lacking lipoxygenases and cyclooxygenases of the production of 10-hydroxy-octadecadienoic acid and that of 1-octen-3-ol, a common volatile compound. Importantly, this was correlated with the inability of the mutants to repel nematodes as efficiently as the wild type. Overall, our data show that in this fungus, oxylipins are not involved in signalling development but may rather be used directly or as precursors in the production of odors against potential agressors.

Maurer's clefts: a novel multi-functional organelle in the cytoplasm of Plasmodium falciparum-infected erythrocytes

Discovered in 1902 by Georg Maurer as a peculiar dotted staining pattern observable by light microscopy in the cytoplasm of erythrocytes infected with the human malarial parasite Plasmodium falciparum, the function of Maurer's clefts have remained obscure for more than a century. The growing interest in protein sorting and trafficking processes in malarial parasites has recently aroused the Maurer's clefts from their deep slumber. Mounting evidence suggests that Maurer's clefts are a secretory organelle, which the parasite establishes within its host erythrocyte, but outside its own confines, to route parasite proteins across the host cell cytoplasm to the erythrocyte surface where they play a role in nutrient uptake and immune evasion processes. Moreover, Maurer's clefts seem to play a role in cell signaling, merozoite egress, phospholipid biosynthesis and, possibly, other biochemical pathways. Here, we review our current knowledge of the ultrastructure of Maurer's clefts, their proteinaceous composition and their function in protein trafficking.     

SMC is recruited to oriC by ParB and promotes chromosome segregation in Streptococcus pneumoniae

Segregation of replicated chromosomes is an essential process in all organisms. How bacteria, such as the oval-shaped human pathogen Streptococcus pneumoniae, efficiently segregate their chromosomes is poorly understood. Here we show that the pneumococcal homologue of the DNA-binding protein ParB recruits S. pneumoniae condensin (SMC) to centromere-like DNA sequences (parS) that are located near the origin of replication, in a similar fashion as was shown for the rod-shaped model bacterium Bacillus subtilis. In contrast to B. subtilis, smc is not essential in S. pneumoniae, and Δsmc cells do not show an increased sensitivity to gyrase inhibitors or high temperatures. However, deletion of smc and/or parB results in a mild chromosome segregation defect. Our results show that S. pneumoniae contains a functional chromosome segregation machine that promotes efficient chromosome segregation by recruitment of SMC via ParB. Intriguingly, the data indicate that other, as of yet unknown mechanisms, are at play to ensure proper chromosome segregation in this organism.     

Fluctuations of Serum Neuron Specific Enolase and Protein S-100B Concentrations in Relation to the Use of Shunt during Carotid Endarterectomy

Objective

To evaluate the changes in serum neuron specific enolase and protein S-100B, after carotid endarterectomy performed using the conventional technique with routine shunting and patch closure, or eversion technique without the use of shunt.

Materials and Methods

Prospective non-randomized study included 43 patients with severe (>80%) carotid stenosis undergoing carotid endarterectomy in regional anesthesia. Patients were divided into two groups: conventional endarterectomy with routine use of shunt and Dacron patch (csCEA group) and eversion endarterectomy without the use of shunt (eCEA group). Protein S-100B and NSE concentrations were measured from peripheral blood before carotid clamping, after declamping and 24 hours after surgery.

Results

Neurologic examination and brain CT findings on the first postoperative day did not differ from preoperative controls in any patients. In csCEA group, NSE concentrations decreased after declamping (P<0.01), and 24 hours after surgery (P<0.01), while in the eCEA group NSE values slightly increased (P=ns), accounting for a significant difference between groups on the first postoperative day (P=0.006). In both groups S-100B concentrations significantly increased after declamping (P<0.05), returning to near pre-clamp values 24 hours after surgery (P=ns). Sub-group analysis revealed significant decline of serum NSE concentrations in asymptomatic patients shunted during surgery after declamping (P<0.05) and 24 hours after surgery (P<0.01), while no significant changes were noted in non-shunted patients (P=ns). Decrease of NSE serum levels was also found in symptomatic patients operated with the use of shunt on the first postoperative day (P<0.05). Significant increase in NSE serum levels was recorded in non-shunted symptomatic patients 24 hours after surgery (P<0.05).

Conclusion

Variations of NSE concentrations seemed to be influenced by cerebral perfusion alterations, while protein S-100B values were unaffected by shunting strategy. Routine shunting during surgery for symptomatic carotid stenosis may have the potential to prevent postoperative increase of serum NSE levels, a potential marker of brain injury.     

Expression and subcellular localization of a 35-kDa carbonic anhydrase IV in a human pancreatic ductal cell line (Capan-1).

The high intraluminal concentrations of HCO(3)(-) in the human pancreatic ducts have suggested the existence of a membrane protein supplying the Cl(-)/HCO(3)(-) exchanger. Membrane-bound carbonic anhydrase IV (CA IV) is one of the potential candidates for this protein. The difficulties in isolating human pancreatic ducts have led the authors to study the molecular mechanisms of HCO(3)(-) secretion in cancerous cell lines. In this work, we have characterized the CA IV expressed in Capan-1 cells. A 35-kDa CA IV was detected in cell homogenates and purified plasma membranes. Treatment of purified plasma membranes with phosphatidylinositol-phospholipase-C indicated that this CA IV was not anchored by a glycosylphosphatidylinositol (GPI). In contrast, its detection on purified plasma membranes by an antibody specifically directed against the carboxyl terminus of human immature GPI-anchored CA IV indicated that it was anchored by a C-terminal hydrophobic segment. Immunoelectron microscopy and double-labeling immunofluorescence revealed that this CA IV was present on apical plasma membranes, and in the rough endoplasmic reticulum, the endoplasmic reticulum-Golgi intermediate compartment, the Golgi complex, and secretory granules, suggesting its transport via the classical biosynthesis/secretory pathway. The expression in Capan-1 cells of a 35-kDa CA IV anchored in the apical plasma membrane through a hydrophobic segment, as is the case in the healthy human pancreas, should make the study of its role in pancreatic HCO(3)(-) secretion easier.