Knobs at the surface of erythrocytes infected with Plasmodium falciparum have been proposed to be important in adherence of these cells to the vascular endothelium. This structure contains the knob-associated histidine-rich protein (KAHRP) and the adhesion receptor P. falciparum erythrocyte membrane protein 1. We have disrupted the gene encoding KAHRP and show that it is essential for knob formation. Knob-transfectants adhere to CD36 in static assays; when tested under flow conditions that mimic those of postcapillary venules, however, the binding to CD36 was dramatically reduced. These data suggest that knobs on P. falciparum-infected erythrocytes exert an important influence on adherence of parasitized-erythrocytes to microvascular endothelium, an important process in the pathogenesis of P. falciparum infections.

Chondroitin sulfate A (CSA) is an important receptor for the sequestration of Plasmodium falciparum in the placenta, but the parasite ligand involved in adhesion has not previously been identified. Here we report the identification of a var gene transcribed in association with binding to CSA and present evidence that the P. falciparum erythrocyte membrane protein 1 product of the gene is the parasite ligand mediating CSA binding. Description of this gene and the implication of P. falciparum erythrocyte membrane protein 1 as the parasite ligand paves the way to a more detailed understanding of the pathogenesis of placental infection and potential therapeutic strategies targeting the interaction.

Adhesion of parasite‐infected red blood cells to the vascular endothelium is a critical event in the pathogenesis of malaria caused by Plasmodium falciparum. Adherence is mediated by the variant erythrocyte membrane protein 1 (PfEMP1). Another protein, erythrocyte membrane protein‐3 (PfEMP3), is deposited under the membrane of the parasite‐infected erythrocyte but its function is unknown. Here we show that mutation of PfEMP3 disrupts transfer of PfEMP1 to the outside of the P.falciparum‐infected cell. Truncation of the C‐terminal end of PfEMP3 by transfection prevents distribution of this large (>300 kDa) protein around the membrane but does not disrupt trafficking of the protein from the parasite to the cytoplasmic face of the erythrocyte membrane. The truncated PfEMP3 accumulates in structures that appear to be associated with the erythrocyte membrane. We show that accumulation of mutated PfEMP3 blocks the transfer of PfEMP1 onto the outside of the parasitized cell surface and suggest that these proteins traffic through an erythrocyte membrane‐associated compartment that is involved in the transfer of PfEMP1 to the surface of the parasite‐infected red blood cell.

Despite decades of study, the molecular mechanisms and selectivity of the biomolecular components of honeybee (Apis mellifera) venom as anticancer agents remain largely unknown. Here, we demonstrate that honeybee venom and its major component melittin potently induce cell death, particularly in the aggressive triple-negative and HER2-enriched breast cancer subtypes. Honeybee venom and melittin suppress the activation of EGFR and HER2 by interfering with the phosphorylation of these receptors in the plasma membrane of breast carcinoma cells. Mutational studies reveal that a positively charged C-terminal melittin sequence mediates plasma membrane interaction and anticancer activity. Engineering of an RGD motif further enhances targeting of melittin to malignant cells with minimal toxicity to normal cells. Lastly, administration of melittin enhances the effect of docetaxel in suppressing breast tumor growth in an allograft model. Our work unveils a molecular mechanism underpinning the anticancer selectivity of melittin, and outlines treatment strategies to target aggressive breast cancers.

authors request that the following correction be noted. Recent nucleotide sequence analysis has established that a C residue was omitted at position 628 of the Sj26 cDNA sequence presented in Fig. 2. The amended nucleotide sequence and the altered prediction of the COOH-terminal structure of Sj26 are given below. This correction does not otherwise affect the conclusions of the paper. ABSTRACT Mice of the inbred strain 129/J bred at this Institute (WEHI 129/J) are relatively resistant to chronic infection with the parasitic helminth Schistosomajaponicum. In contrast to more permissive mouse strains such as BALB/c, the WEHI 129/J mice are high responders to a Mr 26,000 adult worm antigen designated Sj26. Cloned cDNAs corresponding to Sj26 have been identified in a S. japonicum phage Xgtll amp3 expression library, and their nucleotide sequences have been deduced. The predicted amino acid sequence of the antigen specified by these cDNAs shows striking homology with class it isozymes of mammalian glutathione S-transferases (RX:glutathione R-transferase, EC 2.5.1.18). Extracts of adult worms contain glutathione S-transferase activity, and affinity chromatography of enzyme activity on glutathione columns leads to the purification of a Mr 26,000 molecule that comigrates with Sj26. Although vaccination studies in mice with a .3-galactosidase-Sj26 fusion protein from Escherichia coli are encouraging, more immunogenic preparations of the antigen are likely to be required to establish the utility of Sj26 as a model vaccine.

The thymus is essential for a functional immune system, because the thymic stroma uniquely supports T lymphocyte development. We have previously identified the epithelial progenitor population from which the thymus arises and demonstrated its ability to generate an organized functional thymus upon transplantation. These thymic epithelial progenitor cells (TEPC) are defined by surface determinants recognized by the mAbs MTS20 and MTS24, which were also recently shown to identify keratinocyte progenitor cells in the skin. However, the biochemical nature of the MTS20 and MTS24 determinants has remained unknown. Here we show, via expression profiling of fetal mouse TEPC and their differentiated progeny and subsequent analyses, that both MTS20 and MTS24 specifically bind an orphan protein of unknown function, Placenta-expressed transcript (Plet)-1. In the postgastrulation embryo, Plet-1 expression is highly restricted to the developing pharyngeal endoderm and mesonephros until day 11.5 of embryogenesis, consistent with the MTS20 and MTS24 staining pattern; both MTS20 and MTS24 specifically bind cell lines transfected with Plet-1; and antibodies to Plet-1 recapitulate MTS20/24 staining. In adult tissues, we demonstrate expression in a number of sites, including mammary and prostate epithelia and in the pancreas, where Plet-1 is specifically expressed by the major duct epithelium, providing a specific cell surface marker for this putative reservoir of pancreatic progenitor/stem cells. Plet-1 will thus provide an invaluable tool for genetic analysis of the lineage relationships and molecular mechanisms operating in the development, homeostasis, and injury in several organ/tissue systems. thymus development ͉ MTS24 ͉ endoderm ͉ mesonephros

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Immunoglobulin G (IgG) glycosylation is essential for function of the immune system, but the genetic and environmental factors that underlie its inter-individual variability are not well defined. The Collaborative Cross (CC) genetic resource harnesses over 90% of the common genetic variation of the mouse. By analyzing the IgG glycome composition of 95 CC strains, we made several important observations: (i) glycome variation between mouse strains was higher than between individual humans, despite all mice having the same environmental influences; (ii) five genetic loci were found to be associated with murine IgG glycosylation; (iii) variants outside traditional glycosylation site motifs affected glycome variation; (iv) bisecting N-acetylglucosamine (GlcNAc) was produced by several strains although most previous studies have reported the absence of glycans containing the bisecting GlcNAc on murine IgGs; and (v) common laboratory mouse strains are not optimal animal models for studying effects of glycosylation on IgG function.