LncRNA VEAL2 regulates PRKCB2 to modulate endothelial permeability in diabetic retinopathy.

Long non-coding RNAs (lncRNAs) are emerging as key regulators of endothelial cell function. Here, we investigated the role of a novel vascular endothelial-associated lncRNA (VEAL2) in regulating endothelial permeability. Precise editing of veal2 loci in zebrafish (veal2gib005Δ8/+ ) induced cranial hemorrhage. In vitro and in vivo studies revealed that veal2 competes with diacylglycerol for interaction with protein kinase C beta-b (Prkcbb) and regulates its kinase activity. Using PRKCB2 as bait, we identified functional ortholog of veal2 in humans from HUVECs and named it as VEAL2. Overexpression and knockdown of VEAL2 affected tubulogenesis and permeability in HUVECs. VEAL2 was differentially expressed in choroid tissue in eye and blood from patients with diabetic retinopathy, a disease where PRKCB2 is known to be hyperactivated. Further, VEAL2 could rescue the effects of PRKCB2-mediated turnover of endothelial junctional proteins thus reducing hyperpermeability in hyperglycemic HUVEC model of diabetic retinopathy. Based on evidence from zebrafish and hyperglycemic HUVEC models and diabetic retinopathy patients, we report a hitherto unknown VEAL2 lncRNA-mediated regulation of PRKCB2, for modulating junctional dynamics and maintenance of endothelial permeability.

Arachidonic acid metabolism regulates the development of retinopathy of prematurity among preterm infants.

Extremely preterm infants are at risk of developing retinopathy of prematurity (ROP), characterized by neovascularization and neuroinflammation leading to blindness. Polyunsaturated fatty acid (PUFA) supplementation is recommended in preterm infants to lower the risk of ROP, however, with no significant improvement in visual acuity. Reasonably, this could be as a result of the non-consideration of PUFA metabolizing enzymes. We hypothesize that abnormal metabolism of the arachidonic acid (AA) pathway may contribute to severe stages of ROP. The present study investigated the AA-metabolizing enzymes in ROP pathogenesis by a targeted gene expression analysis of blood (severe ROP = 70, No/Mild = 56), placenta (preterm placenta = 6, full term placenta = 3), and human primary retinal cell cultures and further confirmed at the protein level by performing IHC in sections of ROP retina. The lipid metabolites were identified by LC-MS in the vitreous humor (VH; severe ROP = 15, control = 15). Prostaglandins D2 (p = 0.02), leukotrienes B5 (p = 0.0001), 11,12-epoxyeicosatrienoic acid (p = 0.01), and lipid-metabolizing enzymes of the AA pathway such as CYP1B1, CYP2C8, COX2, and ALOX15 were significantly upregulated while EPHX2 was significantly (0.04) downregulated in ROP cases. Genes involved in hypoxic stress, angiogenesis, and apoptosis showed increased expression in ROP. An increase in the metabolic intermediates generated from the AA metabolism pathway further confirmed the role of these enzymes in ROP, while metabolites for EPHX2 activity were low in abundance. Inflammatory lipid intermediates were higher compared to anti-inflammatory lipids in VH and showed an association with enzyme activity. Both the placenta of preterm infants who developed ROP and hypoxic retinal cultures showed a reduced expression of EPHX2. These findings suggested a strong involvement of EPHX2 in regulating retinal neovascularization and inflammation. The study results underscore the role of arachidonic acid metabolism in the development of ROP and as a potential target for preventing vision loss among preterm-born infants.

Identification of lncRNAs regulating seed traits in Brassica juncea and development of a comprehensive seed omics database.

Brassica juncea is a crucial oilseed crop, and its seeds possess high economic value as they are a source of edible oil. In order to understand the role of long non coding RNAs (lncRNAs) in the regulation of seed development, we carried out computational analysis using transcriptome data of developing seeds of two contrasting genotypes of B. juncea, Pusajaikisan (PJK) and Early Heera 2 (EH2). The seeds were sampled at three stages, 15, 30, and 45 days after pollination. We identified 1,539 lncRNAs, of which 809 were differentially expressed. We also carried out extensive characterization and functional analysis of seed lncRNAome. The expression patterns were analysed using k-means clustering, and the targets were analysed using pathway, transcription factor, and GO enrichment, as well as ortholog information. We shortlisted a total of 25 robust lncRNA candidates for seed size, oil content, and seed coat color. We also identified 4 lncRNAs as putative precursors of miRNAs regulating seed development. Moreover, a total of 28 miRNA-lncRNA-mRNA regulatory networks regulating seed traits were identified. We also developed a comprehensive database, (BrassIca juncea database or "BIJ" ( https://bij.cuh.ac.in/ ), which provides seed omics as well as other functional genomics and genetics data in an easily accessible form. These candidate lncRNAs are suitable for including in crop improvement programs through molecular breeding, as well as for future validations through genome editing. Together, the knowledge of these candidate lncRNAs and availability of BIJ database shall leverage the crop improvement efforts in B. juncea.

Plasmodium falciparum cysteine protease Falcipain 3: A potential enzyme for proteolytic processing of histone acetyltransferase PfGCN5.

In spite of 150 years of studying malaria, the unique features of the malarial parasite, Plasmodium, still perplex researchers. One of the methods by which the parasite manages its gene expression is epigenetic regulation, the champion of which is PfGCN5, an essential enzyme responsible for acetylating histone proteins. PfGCN5 is a ∼170 kDa chromatin-remodeling enzyme that harbors the conserved bromodomain and acetyltransferase domain situated in its C-terminus domain. Although the PfGCN5 proteolytic processing is essential for its activity, the specific protease involved in this process still remains elusive. Identification of PfGCN5 interacting proteins through immunoprecipitation (IP) followed by LC-tandem mass spectrometry analysis revealed the presence of food vacuolar proteins, such as the cysteine protease Falcipain 3 (FP3), in addition to the typical members of the PfGCN5 complex. The direct interaction between FP3 and PfGCN5 was further validated by in vitro pull-down assay as well as IP assay. Subsequently, use of cysteine protease inhibitor E64d led to the inhibition of protease-specific processing of PfGCN5 with concomitant enrichment and co-localization of PfGCN5 and FP3 around the food vacuole as evidenced by confocal microscopy as well as electron microscopy. Remarkably, the proteolytic cleavage of the nuclear protein PfGCN5 by food vacuolar protease FP3 is exceptional and atypical in eukaryotic organisms. Targeting the proteolytic processing of GCN5 and the associated protease FP3 could provide a novel approach for drug development aimed at addressing the growing resistance of parasites to current antimalarial drugs.

Potential Involvements of Cilia-Centrosomal Genes in Primary Congenital Glaucoma.

Primary congenital glaucoma (PCG) occurs in children due to developmental abnormalities in the trabecular meshwork and anterior chamber angle. Previous studies have implicated rare variants in CYP1B1, LTBP2, and TEK and their interactions with MYOC, FOXC1, and PRSS56 in the genetic complexity and clinical heterogeneity of PCG. Given that some of the gene-encoded proteins are localized in the centrosomes (MYOC) and perform ciliary functions (TEK), we explored the involvement of a core centrosomal protein, CEP164, which is responsible for ocular development and regulation of intraocular pressure. Deep sequencing of CEP164 in a PCG cohort devoid of homozygous mutations in candidate genes (n = 298) and controls (n = 1757) revealed CEP164 rare pathogenic variants in 16 cases (5.36%). Co-occurrences of heterozygous alleles of CEP164 with other genes were seen in four cases (1.34%), and a physical interaction was noted for CEP164 and CYP1B1 in HEK293 cells. Cases of co-harboring alleles of the CEP164 and other genes had a poor prognosis compared with those with a single copy of the CEP164 allele. We also screened INPP5E, which synergistically interacts with CEP164, and observed a lower frequency of pathogenic variants (0.67%). Our data suggest the potential involvements of CEP164 and INPP5E and the yet unexplored cilia-centrosomal functions in PCG pathogenesis.

Plasmodium falciparum PhIL1-associated complex plays an essential role in merozoite reorientation and invasion of host erythrocytes.

The human malaria parasite, Plasmodium falciparum possesses unique gliding machinery referred to as the glideosome that powers its entry into the insect and vertebrate hosts. Several parasite proteins including Photosensitized INA-labelled protein 1 (PhIL1) have been shown to associate with glideosome machinery. Here we describe a novel PhIL1 associated protein complex that co-exists with the glideosome motor complex in the inner membrane complex of the merozoite. Using an experimental genetics approach, we characterized the role(s) of three proteins associated with PhIL1: a glideosome associated protein- PfGAPM2, an IMC structural protein- PfALV5, and an uncharacterized protein-referred here as PfPhIP (PhIL1 Interacting Protein). Parasites lacking PfPhIP or PfGAPM2 were unable to invade host RBCs. Additionally, the downregulation of PfPhIP resulted in significant defects in merozoite segmentation. Furthermore, the PfPhIP and PfGAPM2 depleted parasites showed abrogation of reorientation/gliding. However, initial attachment with host RBCs was not affected in these parasites. Together, the data presented here show that proteins of the PhIL1-associated complex play an important role in the orientation of P. falciparum merozoites following initial attachment, which is crucial for the formation of a tight junction and hence invasion of host erythrocytes.

Combining in silico and in vitro approaches to understand the involvement of methylerythritol 4-phosphate and shikimate pathways in Agrobacterium tumefaciens for enhanced coenzyme Q10 production.

AIMS: To perform an integrated comparative analysis of metabolic pathway to understand coenzyme Q10 (CoQ10) production in Agrobacterium tumefaciens. METHODS AND RESULTS: Comparative analysis of the CoQ10 metabolic pathway in 10 organisms using a genome to KEGG orthology program (G2KO) and the KEGG database elucidated the completeness of the production pathway in A. tumefaciens. The specific roles of the key precursors and the enzymes in the metabolic network were subsequently confirmed using pathway inhibitors and enhancers. While the use of fosmidomycin and glyphosate was found to inhibit CoQ10 production by 54.54% to 99%, the supplementation of polyprenyl pyrophosphate of the methylerythritol 4-phosphate pathway and 4-hydroxybenzoate precursor of the shikimate pathway did increse the production of CoQ10 by 2.3-fold. CONCLUSIONS: The present study provides a comprehensive understanding of the CoQ10 biosynthetic pathway in A. tumefaciens, which would assist rational metabolic engineering strategies for augmenting CoQ10 biosynthesis.

Genotoxic and mutagenic potential of 7-methylxanthine: an investigational drug molecule for the treatment of myopia.

7-Methylxanthine (7-MX, CAS No. 552-62-5, purity 99.46%) is the first orally administered drug candidate, which showed anti-myopic activity in different pre-clinical studies. In the present study, we investigated the in-vivo genotoxic and mutagenic toxicity of 7-MX in Wistar rats using comet/single-cell gel electrophoresis, chromosomal aberration and micronucleus assays after oral administration. For the single-dose study (72 h), two doses of 7-MX 300 and 2000 mg/kg body weight were selected. For a repeated dose 28 d study, three doses (250, 500, and 1000 mg/kg) of 7-MX were selected. The doses were administered via oral gavage in the suspension form. Blood and major vital organs such as bone marrow, lung and liver were used to perform comet/single cell gel electrophoresis, chromosomal aberration, and micronucleus assays. The in-vitro Ames test was performed on TA98 and TA100 strains. In the chromosomal aberration study, a non-significant increase in deformities such as stickiness, ring chromosome, and endoreduplication was observed in bone marrow cells of 7-MX treated groups. These chromosomal alterations were observed upon treatment with doses of 2000 mg/kg single dose for 72 h and 1000 mg/kg repeated dose for 28 d. At a dose of 500 mg/kg, DNA damage in terms of tail length, tail moment, % tail DNA and the olive tail moment was also found to be non-significant in 7-MX treated groups. The Ames test showed the non-mutagenic nature of 7-MX in both strains of TA98 and TA100 of Salmonella typhimurium with or without metabolic activation. Thus, the present work is interesting in view of the non- genotoxicity and non-mutagenicity of repeated doses of 7-MX.

Binding of Gtf2i-ß/δ transcription factors to the ARMS2 gene leads to increased circulating HTRA1 in AMD patients and in vitro.

The disease-initiating molecular events for age-related macular degeneration (AMD), a multifactorial retinal disease affecting many millions of elderly individuals worldwide, are still unknown. Of the over 30 risk and protective loci so far associated with AMD through whole genome-wide association studies (GWAS), the Age-Related Maculopathy Susceptibility 2 (ARMS2) gene locus represents one of the most highly associated risk regions for AMD. A unique insertion/deletion (in/del) sequence located immediately upstream of the High Temperature Requirement A1 (HTRA1) gene in this region confers high risk for AMD. Using electrophoretic mobility shift assay (EMSA), we identified that two Gtf2i-ß/δ transcription factor isoforms bind to the cis-element 5'- ATTAATAACC-3' contained in this in/del sequence. The binding of these transcription factors leads to enhanced upregulation of transcription of the secretory serine protease HTRA1 in transfected cells and AMD patient-derived induced pluripotent stem cells (iPSCs). Overexpression of Htra1 in mice using a CAG-promoter demonstrated increased blood concentration of Htra1 protein, caused upregulation of vascular endothelial growth factor (VEGF), and produced a choroidal neovascularization (CNV)-like phenotype. Finally, a comparison of 478 AMD patients to 481 healthy, age-matched controls from Japan, India, Australia, and the USA showed a statistically increased level of secreted HTRA1 blood concentration in AMD patients compared with age-matched controls. Taken together, these results suggest a common mechanism across ethnicities whereby increased systemic blood circulation of secreted serine protease HTRA1 leads to subsequent degradation of Bruch's membrane and eventual CNV in AMD.

Plasmodium falciparum GCN5 acetyltransferase follows a novel proteolytic processing pathway that is essential for its function.

The pathogenesis of human malarial parasite Plasmodium falciparum is interlinked with its timely control of gene expression during its complex life cycle. In this organism, gene expression is partially controlled through epigenetic mechanisms, the regulation of which is, hence, of paramount importance to the parasite. The P. falciparum (Pf)-GCN5 histone acetyltransferase (HAT), an essential enzyme, acetylates histone 3 and regulates global gene expression in the parasite. Here, we show the existence of a novel proteolytic processing for PfGCN5 that is crucial for its activity in vivo We find that a cysteine protease-like enzyme is required for the processing of PfGCN5 protein. Immunofluorescence and immuno-electron microscopy analysis suggest that the processing event occurs in the vicinity of the digestive vacuole of the parasite following its trafficking through the classical ER-Golgi secretory pathway, before it subsequently reaches the nucleus. Furthermore, blocking of PfGCN5 processing leads to the concomitant reduction of its occupancy at the gene promoters and a reduced H3K9 acetylation level at these promoters, highlighting the important correlation between the processing event and PfGCN5 activity. Altogether, our study reveals a unique processing event for a nuclear protein PfGCN5 with unforeseen role of a food vacuolar cysteine protease. This leads to a possibility of the development of new antimalarials against these targets.This article has an associated First Person interview with the first author of the paper.

Molecular changes associated with migratory departure from wintering areas in obligate songbird migrants.

Day length regulates the development of spring migratory and subsequent reproductive phenotypes in avian migrants. This study used molecular approaches, and compared mRNA and proteome-wide expression in captive redheaded buntings that were photostimulated under long-day (LD) conditions for 4 days (early stimulated, LD-eS) or for ∼3 weeks until each bird had shown 4 successive nights of Zugunruhe (stimulated, LD-S); controls were maintained under short days. After ∼3 weeks of LD, photostimulated indices of the migratory preparedness (fattening, weight gain and Zugunruhe) were paralleled with upregulated expression of acc, dgat2 and apoa1 genes in the liver, and of cd36, fabp3 and cpt1 genes in the flight muscle, suggesting enhanced fatty acid (FA) synthesis and transport in the LD-S state. Concurrently, elevated expression of genes involved in the calcium ion signalling and transport (camk1 and atp2a2; camk2a in LD-eS), cellular stress (hspa8 and sod1, not nos2) and metabolic pathways (apoa1 and sirt1), but not of genes associated with migratory behaviour (adcyap1 and vps13a), were found in the mediobasal hypothalamus (MBH). Further, MBH-specific quantitative proteomics revealed that out of 503 annotated proteins, 28 were differentially expressed (LD-eS versus LD-S: 21 up-regulated and 7 down-regulated) and they enriched five physiological pathways that are associated with FA transport and metabolism. These first comprehensive results on gene and protein expression suggest that changes in molecular correlates of FA transport and metabolism may aid the decision for migratory departure from wintering areas in obligate songbird migrants.

Plasmodium falciparum Clag9-Associated PfRhopH Complex Is Involved in Merozoite Binding to Human Erythrocytes.

Cytoadherence-linked asexual gene 9 (Clag9), a conserved Plasmodium protein expressed during the asexual blood stages, is involved in the cytoadherence of infected red blood cells (RBCs) to the endothelial lining of blood vessels. Here, we show that Plasmodium falciparum Clag9 (PfClag9) is a component of the PfClag9-RhopH complex that is involved in merozoite binding to human erythrocytes. To characterize PfClag9, we expressed four fragments of PfClag9, encompassing the entire protein. Immunostaining analysis using anti-PfClag9 antibodies showed expression and localization of PfClag9 at the apical end of the merozoites. Mass spectrometric analysis of merozoite extracts after immunoprecipitation using anti-PfClag9 antibody identified P. falciparum rhoptry-associated protein 1 (PfRAP1), PfRAP2, PfRAP3, PfRhopH2, and PfRhopH3 as associated proteins. The identified rhoptry proteins were expressed, and their association with PfClag9 domains was assessed by using protein-protein interaction tools. We further showed that PfClag9 binds human RBCs by interacting with the glycophorin A-band 3 receptor-coreceptor complex. In agreement with its cellular localization, PfClag9 was strongly recognized by antibodies generated during natural infection. Mice immunized with the C-terminal domain of PfClag9 were partially protected against a subsequent challenge infection with Plasmodium berghei, further supporting a biological role of PfClag9 during natural infection. Taken together, these results provide direct evidence for the existence of a PfRhopH-Clag9 complex on the Plasmodium merozoite surface that binds to human RBCs.

Maternal and perinatal mortality and complications associated with caesarean section in low-income and middle-income countries: a systematic review and meta-analysis.

BACKGROUND: Universal and timely access to a caesarean section is a key requirement for safe childbirth. We identified the burden of maternal and perinatal mortality and morbidity, and the risk factors following caesarean sections in low-income and middle-income countries (LMICs). METHODS: For this systematic review and meta-analysis, we searched electronic databases including MEDLINE and Embase (from Jan 1, 1990, to Nov 20, 2017), without language restrictions, for studies on maternal or perinatal outcomes following caesarean sections in LMICs. We excluded studies in high-income countries, those involving non-pregnant women, case reports, and studies published before 1990. Two reviewers undertook the study selection, quality assessment, and data extraction independently. The main outcome being assessed was prevalence of maternal mortality in women undergoing caesarean sections in LMICs. We used a random effects model to synthesise the rate data, and reported the association between risk factors and outcomes using odds ratios with 95% CIs. The study protocol has been registered with PROSPERO, number CRD42015029191. FINDINGS: We included 196 studies from 67 LMICs. The risk of maternal death in women who had a caesarean section (116 studies, 2 933 457 caesarean sections) was 7·6 per 1000 procedures (95% CI 6·6-8·6, τ2=0·81); the highest burden was in sub-Saharan Africa (10·9 per 1000; 9·5-12·5, τ2=0·81). A quarter of all women who died in LMICs (72 studies, 27 651 deaths) had undergone a caesarean section (23·8%, 95% CI 21·0-26·7; τ2=0·62). INTERPRETATION: Maternal deaths and perinatal deaths following caesarean sections are disproportionately high in LMICs. The timing and urgency of caesarean section pose major risks. FUNDING: Ammalife Charity and ELLY Appeal, Barts Charity, and the UK National Institute for Health Research.

Calcium-dependent phosphorylation of Plasmodium falciparum serine repeat antigen 5 triggers merozoite egress.

The human malaria parasite Plasmodium falciparum proliferates in red blood cells following repeated cycles of invasion, multiplication, and egress. P. falciparum serine repeat antigen 5 (PfSERA5), a putative serine protease, plays an important role in merozoite egress. However, regulation of its activity leading to merozoite egress is poorly understood. In this study, we show that PfSERA5 undergoes phosphorylation prior to merozoite egress. Immunoprecipitation of parasite lysates using anti-PfSERA5 serum followed by MS analysis identified calcium-dependent protein kinase 1 (PfCDPK1) as an interacting kinase. Association of PfSERA5 with PfCDPK1 was corroborated by co-sedimentation, co-immunoprecipitation, and co-immunolocalization analyses. Interestingly, PfCDPK1 phosphorylated PfSERA5 in vitro in the presence of Ca2+ and enhanced its proteolytic activity. A PfCDPK1 inhibitor, purfalcamine, blocked the phosphorylation and activation of PfSERA5 both in vitroas well as in schizonts, which, in turn, blocked merozoite egress. Together, these results suggest that phosphorylation of PfSERA5 by PfCDPK1 following a rise in cytosolic Ca2+ levels activates its proteolytic activity to trigger merozoite egress.

The N-terminal domain of unknown function (DUF959) in collagen XVIII is intrinsically disordered and highly O-glycosylated.

Collagen XVIII (ColXVIII) is a non-fibrillar collagen and proteoglycan that exists in three isoforms: short, medium and long. The medium and long isoforms contain a unique N-terminal domain of unknown function, DUF959, and our sequence-based secondary structure predictions indicated that DUF959 could be an intrinsically disordered domain. Recombinant DUF959 produced in mammalian cells consisted of ∼50% glycans and had a molecular mass of 63 kDa. Circular dichroism spectroscopy confirmed the disordered character of DUF959, and static light scattering indicated a monomeric state for glycosylated DUF959 in solution. Small-angle X-ray scattering showed DUF959 to be a highly extended, flexible molecule with a maximum dimension of ∼23 nm. Glycosidase treatment demonstrated considerable amounts of O-glycosylation, and expression of DUF959 in HEK293 SimpleCells capable of synthesizing only truncated O-glycans confirmed the presence of N-acetylgalactosamine-type O-glycans. The DUF959 sequence is characterized by numerous Ser and Thr residues, and this accounts for the finding that half of the recombinant protein consists of glycans. Thus, the medium and long ColXVIII isoforms contain at their extreme N-terminus a disordered, elongated and highly O-glycosylated mucin-like domain that is not found in other collagens, and we suggest naming it the Mucin-like domain in ColXVIII (MUCL-C18). As intrinsically disordered regions and their post-translational modifications are often involved in protein interactions, our findings may point towards a role of the flexible mucin-like domain of ColXVIII as an interaction hub affecting cell signaling. Moreover, the MUCL-C18 may also serve as a lubricant at cell-extracellular matrix interfaces.

Comparative evaluation of the aqueous humor proteome of primary angle closure and primary open angle glaucomas and age-related cataract eyes.

PURPOSE: To analyze and compare the total proteome of aqueous humor (AH) from patients having primary angle closure glaucoma (PACG), primary open angle glaucoma (POAG) and age-related cataract. MATERIALS AND METHODOLOGY: Aqueous humor was collected from age-matched PACG, POAG and cataract patients who underwent surgery, and it was immediately stored at - 80 °C until analysis. From each sample, 25 µg of total protein was subjected to trypsin digestion and subsequently LC-MS/MS analysis was performed for the deep proteome analysis. The data acquired after the LC-MS/MS analysis were analyzed using Proteome Discoverer 1.4. The identified peptide matches were validated using percolator, at less than 1% false discovery rates. RESULTS: A total of 625, 594 and 636 proteins were identified in PACG, POAG and cataract groups, respectively (n = 9 in each group). The inter-group comparison among all these groups showed that 246 proteins were identified in all the three groups. An average of 236 ± 42, 218 ± 40 and 214 ± 62 proteins from each AH sample of PACG, POAG and cataract, respectively, was identified. There were 53 proteins commonly found in all 9 PACG AH, 59 proteins in POAG AH and 42 proteins in 9 cataracts AH samples. In the individual analysis, there were 28 proteins found in all the samples analyzed representing the "constitutive AH proteome." Spectral counting analysis of 246 proteins identified in all three group types showed significant differences in protein abundance. In proteins unique to PACG AH, 7 proteins viz. ARHGEF12, APC2, WAS, PIK3CG, ITGB1, MSN and PFN1 out of 226 were found in "Regulation of Actin Cytoskeleton" pathway, whereas in POAG 5 out of 206 proteins viz. ADCY2, ITPR1, MAPK3, MAP3K2 and TUBB1 were found in "Gap Junction" pathway. CONCLUSIONS: A qualitative as well as a quantitative comparison of proteomes of AH from PACG, POAG and age-related cataract eyes showed significant differences, thus providing clues to the disease pathophysiology.

Basigin Interacts with Plasmodium vivax Tryptophan-rich Antigen PvTRAg38 as a Second Erythrocyte Receptor to Promote Parasite Growth.

Elucidating the molecular mechanisms of the host-parasite interaction during red cell invasion by Plasmodium is important for developing newer antimalarial therapeutics. Recently, we have characterized a Plasmodium vivax tryptophan-rich antigen PvTRAg38, which is expressed by its merozoites, binds to host erythrocytes, and interferes with parasite growth. Interaction of this parasite ligand with the host erythrocyte occurs through its two regions present at amino acid positions 167-178 (P2) and 197-208 (P4). Each region recognizes its own erythrocyte receptor. Previously, we identified band 3 as the chymotrypsin-sensitive erythrocyte receptor for the P4 region, but the other receptor, binding to P2 region, remained unknown. Here, we have identified basigin as the second erythrocyte receptor for PvTRAg38, which is resistant to chymotrypsin. The specificity of interaction between PvTRAg38 and basigin was confirmed by direct interaction where basigin was specifically recognized by P2 and not by the P4 region of this parasite ligand. Interaction between P2 and basigin is stabilized through multiple amino acid residues, but Gly-171 and Leu-175 of P2 were more critical. These two amino acids were also critical for parasite growth. Synthetic peptides P2 and P4 of PvTRAg38 interfered with the parasite growth independently but had an additive effect if combined together indicating involvement of both the receptors during red cell invasion. In conclusion, PvTRAg38 binds to two erythrocyte receptors basigin and band 3 through P2 and P4 regions, respectively, to facilitate parasite growth. This advancement in our knowledge on molecular mechanisms of host-parasite interaction can be exploited to develop therapeutics against P. vivax malaria.

Plasmodium falciparum MSP3 Exists in a Complex on the Merozoite Surface and Generates Antibody Response during Natural Infection.

Plasmodium falciparum merozoite surface protein 3 (MSP3) is an abundantly expressed secreted merozoite surface protein and a leading malaria vaccine candidate antigen. However, it is unclear how MSP3 is retained on the surface of merozoites without a glycosylphosphatidylinositol (GPI) anchor or a transmembrane domain. In the present study, we identified an MSP3-associated network on the Plasmodium merozoite surface by immunoprecipitation of Plasmodium merozoite lysate using antibody to the N terminus of MSP3 (anti-MSP3N) followed by mass spectrometry analysis. The results suggested the association of MSP3 with other merozoite surface proteins: MSP1, MSP6, MSP7, RAP2, and SERA5. Protein-protein interaction studies by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) analysis showed that MSP3 complex consists of MSP1, MSP6, and MSP7 proteins. Immunological characterization of MSP3 revealed that MSP3N is strongly recognized by hyperimmune serum from African and Asian populations. Furthermore, we demonstrate that human antibodies, affinity purified against recombinant MSP3N (rMSP3N), promote opsonic phagocytosis of merozoites in cooperation with monocytes. At nonphysiological concentrations, anti-MSP3N antibodies inhibited the growth of P. falciparum in vitro Together, the data suggest that MSP3 and especially its N-terminal region containing known B/T cell epitopes are targets of naturally acquired immunity against malaria and also comprise an important candidate for a multisubunit malaria vaccine.

Proteomic Identification and Analysis of Arginine-Methylated Proteins of Plasmodium falciparum at Asexual Blood Stages.

Plasmodium falciparum undergoes a tightly regulated developmental process in human erythrocytes, and recent studies suggest an important regulatory role of post-translational modifications (PTMs). As compared with Plasmodium phosphoproteome, little is known about other PTMs in the parasite. In the present study, we performed a global analysis of asexual blood stages of Plasmodium falciparum to identify arginine-methylated proteins. Using two different methyl arginine-specific antibodies, we immunoprecipitated the arginine-methylated proteins from the stage-specific parasite lysates and identified 843 putative arginine-methylated proteins by LC-MS/MS. Motif analysis of the protein sequences unveiled that the methylation sites are associated with the previously known methylation motifs such as GRx/RGx, RxG, GxxR, or WxxxR. We identified Plasmodium homologues of known arginine-methylated proteins in trypanosomes, yeast, and human. Hydrophilic interaction liquid chromatography (HILIC) was performed on the immunoprecipitates from the trophozoite stage to enrich arginine-methylated peptides. Mass spectrometry analysis of immunoprecipitated and HILIC fractions identified 55 arginine-methylated peptides having 62 methylated arginine sites. Functional classification revealed that the arginine-methylated proteins are involved in RNA metabolism, protein synthesis, intracellular protein trafficking, proteolysis, protein folding, chromatin organization, hemoglobin metabolic process, and several other functions. Summarily, the findings suggest that protein methylation of arginine residues is a widespread phenomenon in Plasmodium, and the PTM may play an important regulatory role in a diverse set of biological pathways, including host-pathogen interactions.

Angiopoietin receptor TEK interacts with CYP1B1 in primary congenital glaucoma.

Primary congenital glaucoma (PCG) is a severe autosomal recessive ocular disorder associated with considerable clinical and genetic heterogeneity. Recently, rare heterozygous alleles in the angiopoietin receptor-encoding gene TEK were implicated in PCG. We undertook this study to ascertain the second mutant allele in a large cohort (n = 337) of autosomal recessive PCG cases that carried heterozygous TEK mutations. Our investigations revealed 12 rare heterozygous missense mutations in TEK by targeted sequencing. Interestingly, four of these TEK mutations (p.E103D, p.I148T, p.Q214P, and p.G743A) co-occurred with three heterozygous mutations in another major PCG gene CYP1B1 (p.A115P, p.E229K, and p.R368H) in five families. The parents of these probands harbored either of the heterozygous TEK or CYP1B1 alleles and were asymptomatic, indicating a potential digenic mode of inheritance. Furthermore, we ascertained the interactions of TEK and CYP1B1 by co-transfection and pull-down assays in HEK293 cells. Ligand responsiveness of the wild-type and mutant TEK proteins was assessed in HUVECs using immunofluorescence analysis. We observed that recombinant TEK and CYP1B1 proteins interact with each other, while the disease-associated allelic combinations of TEK (p.E103D)::CYP1B1 (p.A115P), TEK (p.Q214P)::CYP1B1 (p.E229K), and TEK (p.I148T)::CYP1B1 (p.R368H) exhibit perturbed interaction. The mutations also diminished the ability of TEK to respond to ligand stimulation, indicating perturbed TEK signaling. Overall, our data suggest that interaction of TEK and CYP1B1 contributes to PCG pathogenesis and argue that TEK-CYP1B1 may perform overlapping as well as distinct functions in manifesting the disease etiology.