Structural studies of human glioma pathogenesis-related protein 1

CAP superfamily proteins in human: a new target for cancer therapy

The CAP (Cysteine-rich secretory protein, Antigen 5, and Pathogenesis-related protein 1) superfamily proteins (CAP proteins) are found in all kingdoms of life. The cysteine-rich secreted proteins are prevalent in human organs and tissues and serve as critical signaling molecules within cells, regulating a wide range of biochemical processes in the human body. Due to their involvement in numerous biological processes, CAP proteins have recently attracted significant attention, particularly in the context of tumorigenesis and cancer therapy. This review summarizes the expression patterns and roles of CAP proteins in various cancers. Additionally, it analyzes the mechanisms by which CAP proteins affect cancer cell proliferation and survival, regulate epithelial-mesenchymal transition, influence drug resistance, and regulate epigenetics. The review reveals that CAP proteins play distinct roles in various signaling pathways, such as the MAPK, PI3K-Akt, and p53 pathways, which are crucial for tumor progression. Furthermore, this review summarizes the tumor-inhibiting function of CAP proteins and their potential as cancer biomarkers. These findings suggest that CAP proteins represent a promising new target for innovative cancer diagnosis and treatment.

Alpha-1-B glycoprotein (A1BG) inhibits sterol-binding and export by CRISP2

Proteins belonging to the CAP superfamily are present in all kingdoms of life and have been implicated in various processes, including sperm maturation and cancer progression. They are mostly secreted glycoproteins and share a unique conserved CAP domain. The precise mode of action of these proteins, however, has remained elusive. Saccharomyces cerevisiae expresses three members of this protein family, which bind sterols in vitro and promote sterol secretion from cells. This sterol-binding and export function of yeast Pry proteins is conserved in the mammalian CRISP proteins and other CAP superfamily members. CRISP3 is an abundant protein of the human seminal plasma and interacts with alpha-1-B glycoprotein (A1BG), a human plasma glycoprotein that is upregulated in different types of cancers. Here we examined whether the interaction between CRISP proteins and A1BG affects the sterol-binding function of CAP family members. Co-expression of A1BG with CAP proteins abolished their sterol export function in yeast and their interaction inhibits sterol-binding in vitro. We map the interaction between A1BG and CRISP2 to the third of five repeated immunoglobulin-like (Ig) domains within A1BG. Interestingly, the interaction between A1BG and CRISP2 requires magnesium, suggesting that coordination of Mg2+ by the highly conserved tetrad residues within the CAP domain is essential for a stable interaction between the two proteins. The observation that A1BG modulates the sterol-binding function of CRISP2, has potential implications for the role of A1BG and related Ig domain containing proteins in cancer progression and the toxicity of reptile venoms containing CRISP proteins.

A member of the CAP protein superfamily, Hc-CAP-15, is important for the parasitic-stage development of Haemonchus contortus

BACKGROUND

The CAP superfamily proteins are distributed widely in eukaryotes and play crucial roles in various biological processes. However, very little is known about their functions in parasitic nematodes, including Haemonchus contortus, a socioeconomically important parasitic nematode. We have therefore studied a member of the CAP protein family of H. contortus, named Hc-CAP-15, with the aim to explore its roles in regulating the parasitic developmental process.

METHODS

The conservation and phylogenetic relationships, spatial expression and temporal transcription profiles of Hc-CAP/cap-15, as well its biological function during parasite development were investigated using bioinformatics, immunofluorescence, real-time PCR and RNA interference (RNAi).

RESULTS

Hc-CAP-15 was found to be a single-domain CAP protein consisting of four conserved motifs that is localized in the cuticle, intestine and oocyte of adult worms. Hc-cap-15 was transcribed at all developmental stages of H. contortus, with the highest transcription level in parasitic fourth-stage larvae (L4s). Silencing of Hc-cap-15 resulted in a significant increase in the body length of L4s.

CONCLUSIONS

The results suggested that Hc-CAP-15 is important for the development of H. contortus. Our findings provide a basis for further study of the functions of the CAP family proteins in H. contortus and related parasitic nematodes.

The function of plant PR1 and other members of the CAP protein superfamily in plant-pathogen interactions

The pathogenesis-related (PR) proteins of plants have originally been identified as proteins that are strongly induced upon biotic and abiotic stress. These proteins fall into 17 distinct classes (PR1-PR17). The mode of action of most of these PR proteins has been well characterized, except for PR1, which belongs to a widespread superfamily of proteins that share a common CAP domain. Proteins of this family are not only expressed in plants but also in humans and in many different pathogens, including phytopathogenic nematodes and fungi. These proteins are associated with a diverse range of physiological functions. However, their precise mode of action has remained elusive. The importance of these proteins in immune defence is illustrated by the fact that PR1 overexpression in plants results in increased resistance against pathogens. However, PR1-like CAP proteins are also produced by pathogens and deletion of these genes results in reduced virulence, suggesting that CAP proteins can exert both defensive and offensive functions. Recent progress has revealed that plant PR1 is proteolytically cleaved to release a C-terminal CAPE1 peptide, which is sufficient to activate an immune response. The release of this signalling peptide is blocked by pathogenic effectors to evade immune defence. Moreover, plant PR1 forms complexes with other PR family members, including PR5, also known as thaumatin, and PR14, a lipid transfer protein, to enhance the host's immune response. Here, we discuss possible functions of PR1 proteins and their interactors, particularly in light of the fact that these proteins can bind lipids, which have important immune signalling functions.

Key genes and drug delivery systems to improve the efficiency of chemotherapy

Cancer cells can develop resistance to anticancer drugs, thereby becoming tolerant to treatment through different mechanisms. The biological mechanisms leading to the generation of anticancer treatment resistance include alterations in transmembrane proteins, DNA damage and repair mechanisms, alterations in target molecules, and genetic responses, among others. The most common anti-cancer drugs reported to develop resistance to cancer cells include cisplatin, doxorubicin, paclitaxel, and fluorouracil. These anticancer drugs have different mechanisms of action, and specific cancer types can be affected by different genes. The development of drug resistance is a cellular response which uses differential gene expression, to enable adaptation and survival of the cell to diverse threatening environmental agents. In this review, we briefly look at the key regulatory genes, their expression, as well as the responses and regulation of cancer cells when exposed to anticancer drugs, along with the incorporation of alternative nanocarriers as treatments to overcome anticancer drug resistance.

Glioma pathogenesis-related protein 1 performs dual functions in tumor cells

Glioma pathogenesis-related protein 1 (GLIPR1) was identified as an oncoprotein in some cancer types including gliomas, breast cancers, melanoma cancers, and Wilms tumors, but as a tumor suppressor in some other types of cancers, such as prostate cancers, lung cancers, bladder cancers, and thyroid cancers. In gliomas, GLIPR1 promotes the migration and invasion of glioma cells by interaction with the actin polymerization regulator Neural Wiskott-Aldrich syndrome protein (N-WASP) and then abolishes the negative effects of Heterogeneous nuclear ribonuclear protein K (hnRNPK). In prostate cancers, high levels of GLIPR1 induce apoptosis and destruction of oncoproteins. In lung cancers, overexpression of GLIPR1 inhibits the growth of lung cancer cells partially through inhibiting the V-ErbB avian erythroblastic leukemia viral oncogene homolog3 (ErbB3) pathway. However, the mechanisms that GLIPR1 performs its function in other tumors still remain unclear. The tumor suppressing role of GLIPR1 has been explored to the cancer treatment. The adenoviral vector-mediated Glipr1 (AdGlipr1) gene therapy and the GLIPR1-transmembrane domain deleted (GLIPR1-ΔTM) protein therapy both showed antitumor activities and stimulated immune response in prostate cancers. Whether GLPIR1 can be used to treat other tumors is an important topic to be explored. Among which, whether GLPIR1 can be used to treat lung cancer by atomizing inhalation is the key topic we care about. If it does, this therapy has a wide application prospect and is a great progression in lung cancer treatment.

The less conserved metal-binding site in human CRISP1 remains sensitive to zinc ions to permit protein oligomerization

Cysteine-rich secretory proteins (CRISPs) are a subgroup of the CRISP, antigen 5 and PR-1 (CAP) superfamily that is characterized by the presence of a conserved CAP domain. Two conserved histidines in the CAP domain are proposed to function as a Zn²⁺-binding site with unknown function. Human CRISP1 is, however, one of the few family members that lack one of these characteristic histidine residues. The Zn²⁺-dependent oligomerization properties of human CRISP1 were investigated using a maltose-binding protein (MBP)-tagging approach in combination with low expression levels in XL-1 Blue bacteria. Moderate yields of soluble recombinant MBP-tagged human CRISP1 (MBP-CRISP1) and the MBP-tagged CAP domain of CRISP1 (MBP-CRISP1^ΔC) were obtained. Zn²⁺ specifically induced oligomerization of both MBP-CRISP1 and MBP-CRISP1^ΔC in vitro. The conserved His142 in the CAP domain was essential for this Zn²⁺ dependent oligomerization process, confirming a role of the CAP metal-binding site in the interaction with Zn²⁺. Furthermore, MBP-CRISP1 and MBP-CRISP1^ΔC oligomers dissociated into monomers upon Zn²⁺ removal by EDTA. Condensation of proteins is characteristic for maturing sperm in the epididymis and this process was previously found to be Zn²⁺-dependent. The Zn²⁺-induced oligomerization of human recombinant CRISP1 may shed novel insights into the formation of functional protein complexes involved in mammalian fertilization.

The functions of CAP superfamily proteins in mammalian fertility and disease

BACKGROUND

Members of the cysteine-rich secretory proteins (CRISPS), antigen 5 (Ag5) and pathogenesis-related 1 (Pr-1) (CAP) superfamily of proteins are found across the bacterial, fungal, plant and animal kingdoms. Although many CAP superfamily proteins remain poorly characterized, over the past decade evidence has accumulated, which provides insights into the functional roles of these proteins in various processes, including fertilization, immune defence and subversion, pathogen virulence, venom toxicology and cancer biology.

OBJECTIVE AND RATIONALE

The aim of this article is to summarize the current state of knowledge on CAP superfamily proteins in mammalian fertility, organismal homeostasis and disease pathogenesis.

SEARCH METHODS

The scientific literature search was undertaken via PubMed database on all articles published prior to November 2019. Search terms were based on following keywords: 'CAP superfamily', 'CRISP', 'Cysteine-rich secretory proteins', 'Antigen 5', 'Pathogenesis-related 1', 'male fertility', 'CAP and CTL domain containing', 'CRISPLD1', 'CRISPLD2', 'bacterial SCP', 'ion channel regulator', 'CatSper', 'PI15', 'PI16', 'CLEC', 'PRY proteins', 'ASP proteins', 'spermatogenesis', 'epididymal maturation', 'capacitation' and 'snake CRISP'. In addition to that, reference lists of primary and review article were reviewed for additional relevant publications.

OUTCOMES

In this review, we discuss the breadth of knowledge on CAP superfamily proteins with regards to their protein structure, biological functions and emerging significance in reproduction, health and disease. We discuss the evolution of CAP superfamily proteins from their otherwise unembellished prokaryotic predecessors into the multi-domain and neofunctionalized members found in eukaryotic organisms today. At least in part because of the rapid evolution of these proteins, many inconsistencies in nomenclature exist within the literature. As such, and in part through the use of a maximum likelihood phylogenetic analysis of the vertebrate CRISP subfamily, we have attempted to clarify this confusion, thus allowing for a comparison of orthologous protein function between species. This framework also allows the prediction of functional relevance between species based on sequence and structural conservation.

WIDER IMPLICATIONS

This review generates a picture of critical roles for CAP proteins in ion channel regulation, sterol and lipid binding and protease inhibition, and as ligands involved in the induction of multiple cellular processes.

Necator americanus Ancylostoma Secreted Protein-2 (Na-ASP-2) Binds an Ascaroside (ascr#3) in Its Fatty Acid Binding Site

During their infective stages, hookworms release excretory-secretory (E-S) products, small molecules, and proteins to help evade and suppress the host's immune system. Small molecules found in E-S products of mammalian hookworms include nematode derived metabolites like ascarosides, which are composed of the sugar ascarylose linked to a fatty acid side chain. The most abundant proteins found in hookworm E-S products are members of the protein family known as Ancylostoma secreted protein (ASP). In this study, two ascarosides and their fatty acid moieties were synthesized and tested for in vitro binding to Na-ASP-2 using both a ligand competition assay and microscale thermophoresis. The fatty acid moieties of both ascarosides tested and ascr#3, an ascaroside found in rat hookworm E-S products, bind to Na-ASP-2's palmitate binding cavity. These molecules were confirmed to bind to the palmitate but not the sterol binding sites. An ascaroside, oscr#10, which is not found in hookworm E-S products, does not bind to Na-ASP-2. More studies are required to determine the structural basis of ascarosides binding by Na-ASP-2 and to understand the physiological significance of these observations.

Zinc binding regulates amyloid-like aggregation of GAPR-1

Members of the CAP superfamily (Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-related 1 proteins) are characterized by the presence of a CAP domain that is defined by four sequence motifs and a highly conserved tertiary structure. A common structure–function relationship for this domain is hitherto unknown. A characteristic of several CAP proteins is their formation of amyloid-like structures in the presence of lipids. Here we investigate the structural modulation of Golgi-Associated plant Pathogenesis Related protein 1 (GAPR-1) by known interactors of the CAP domain, preceding amyloid-like aggregation. Using isothermal titration calorimetry (ITC), we demonstrate that GAPR-1 binds zinc ions. Zn²⁺ binding causes a slight but significant conformational change as revealed by CD, tryptophan fluorescence, and trypsin digestion. The Zn²⁺-induced conformational change was required for the formation of GAPR-1 oligomers and amyloid-like assemblies in the presence of heparin, as shown by ThT fluorescence and TEM. Molecular dynamics simulations show binding of Zn²⁺ to His⁵⁴ and His¹⁰³. Mutation of these two highly conserved residues resulted in strongly diminished amyloid-like aggregation. Finally, we show that proteins from the cysteine-rich secretory protein (CRISP) subfamily are also able to form ThT-positive structures in vitro in a heparin- and Zn²⁺-dependent manner, suggesting that oligomerization regulated by metal ions could be a common structural property of the CAP domain.

Secreted venom allergen-like proteins of helminths: Conserved modulators of host responses in animals and plants

Despite causing considerable damage to host tissue at the onset of parasitism, invasive helminths establish remarkably persistent infections in both animals and plants. Secretions released by these obligate parasites during host invasion are thought to be crucial for their persistence in infection. Helminth secretions are complex mixtures of molecules, most of which have unknown molecular targets and functions in host cells or tissues. Although the habitats of animal- and plant-parasitic helminths are very distinct, their secretions share the presence of a structurally conserved group of proteins called venom allergen-like proteins (VALs). Helminths abundantly secrete VALs during several stages of parasitism while inflicting extensive damage to host tissue. The tight association between the secretion of VALs and the onset of parasitism has triggered a particular interest in this group of proteins, as improved knowledge on their biological functions may assist in designing novel protection strategies against parasites in humans, livestock, and important food crops.

Molecular Characterization and Functional Analysis of PR-1-Like Proteins Identified from the Wheat Head Blight Fungus Fusarium graminearum

The group 1 pathogenesis-related (PR-1) proteins originally identified from plants and their homologs are also found in other eukaryotic kingdoms. Studies on nonplant PR-1-like (PR-1L) proteins have been pursued widely in humans and animals but rarely in filamentous ascomycetes. Here, we report the characterization of four PR-1L proteins identified from the ascomycete fungus Fusarium graminearum, the primary cause of Fusarium head blight of wheat and barley (designated FgPR-1L). Molecular cloning revealed that the four FgPR-1L proteins are all encoded by small open reading frames (612 to 909 bp) that are often interrupted by introns, in contrast to plant PR-1 genes that lack introns. Sequence analysis indicated that all FgPR-1L proteins contain the PR-1-specific three-dimensional structure, and one of them features a C-terminal transmembrane (TM) domain that has not been reported for any stand-alone PR-1 proteins. Transcriptional analysis revealed that the four FgPR-1L genes are expressed in axenic cultures and in planta with different spatial or temporal expression patterns. Phylogenetic analysis indicated that fungal PR-1L proteins fall into three major groups, one of which harbors FgPR-1L-2-related TM-containing proteins from both phytopathogenic and human-pathogenic ascomycetes. Low-temperature sodium dodecyl sulfate polyacrylamide gel electrophoresis and proteolytic assays indicated that the recombinant FgPR-1L-4 protein exists as a monomer and is resistant to subtilisin of the serine protease family. Functional analysis confirmed that deletion of the FgPR-1L-4 gene from the fungal genome results in significantly reduced virulence on susceptible wheat. This study provides the first example that the F. graminearum-wheat interaction involves a pathogen-derived PR-1L protein that affects fungal virulence on the host.

Crystal structure of Brugia malayi venom allergen-like protein-1 (BmVAL-1), a vaccine candidate for lymphatic filariasis

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The vaccine candidate Brugia malayi venom allergen-like 1 protein (BmVAL-1) has three distinct binding cavities.

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The cavities are the central cavity; the sterol-binding caveolin-binding motif (CBM); and the palmitate-binding cavity.

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These cavities are connected by channels, which can accommodate water molecules, ions and small ligands.

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The channels explain how blocking divalent ions in the central cavity affects sterol binding in the distinct CBM cavity.

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BmVAL-1 has a glycosylated CBM, is an effective sterol transporter in vivo and binds cholesterol and palmitate in vitro.

Brugia malayi is a causative agent of lymphatic filariasis, a major tropical disease. The infective L3 parasite stage releases immunomodulatory proteins including the venom allergen-like proteins (VALs), which are members of the SCP/TAPS (Sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7) superfamily. BmVAL-1 is a major target of host immunity with >90% of infected B. malayi microfilaraemic cases being seropositive for antibodies to BmVAL-1. This study is part of ongoing efforts to characterize the structures and functions of important B. malayi proteins. Recombinant BmVAL-1 was produced using a plant expression system, crystallized and the structure was solved by molecular replacement and refined to 2.1 Å, revealing the characteristic alpha/beta/alpha sandwich topology of eukaryotic SCP/TAPS proteins. The protein has more than 45% loop regions and these flexible loops connect the helices and strands, which are longer than predicted based on other parasite SCP/TAPS protein structures. The large central cavity of BmVAL-1 is a prototypical CRISP cavity with two histidines required to bind divalent cations. The caveolin-binding motif (CBM) that mediates sterol binding in SCP/TAPS proteins is large and open in BmVAL-1 and is N-glycosylated. N-glycosylation of the CBM does not affect the ability of BmVAL-1 to bind sterol in vitro. BmVAL-1 complements the in vivo sterol export phenotype of yeast mutants lacking their endogenous SCP/TAPS proteins. The in vitro sterol-binding affinity of BmVAL-1 is comparable with Pry1, a yeast sterol transporting SCP/TAPS protein. Sterol binding of BmVAL-1 is dependent on divalent cations. BmVAL-1 also has a large open palmitate-binding cavity, which binds palmitate comparably to tablysin-15, a lipid-binding SCP/TAPS protein. The central cavity, CBM and palmitate-binding cavity of BmVAL-1 are interconnected within the monomer with channels that can serve as pathways for water molecules, cations and small molecules.

Heligmosomoides polygyrus Venom Allergen-like Protein-4 (HpVAL-4) is a sterol binding protein

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Heligmosomoides polygyrus Venom Allergen-like Protein-4 (HpVAL-4) was produced in plants as a glycosylated protein.

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The crystal structure of HpVAL-4 was solved and reveals three distinct cavities.

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These cavities are the central cavity; the sterol-binding caveolin-binding motif (CBM); and the palmitate-binding cavity.

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The central cavity of Hp-VAL-4 lacks the characteristic histidines that coordinate divalent cations.

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Hp-VAL-4 binds sterol in vivo and in vitro.

Heligmosomoides polygyrus bakeri is a model parasitic hookworm used to study animal and human helminth diseases. During infection, the parasite releases excretory/secretory products that modulate the immune system of the host. The most abundant protein family in excretory/secretory products comprises the venom allergen-like proteins (VALs), which are members of the SCP/TAPS (sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7) superfamily. There are >30 secreted Heligmosomoides polygyrus VAL proteins (HpVALs) and these proteins are characterised by having either one or two 15 kDa CAP (cysteine-rich secretory protein (CRISP)/antigen 5/pathogenesis related-1) domains. The first known HpVAL structure, HpVAL-4, refined to 1.9 Å is reported. HpVAL-4 was produced as a homogeneously glycosylated protein in leaves of Nicotiana benthamiana infiltrated with recombinant plasmids, making this plant expression platform amenable for the production of biological products. The overall topology of HpVAL-4 is a three layered αβα sandwich between a short N-terminal loop and a C-terminal cysteine rich extension. The C-terminal cysteine rich extension has two strands stabilized by two disulfide bonds and superposes well with the previously reported extension from the human hookworm Necator americanus Ancylostoma secreted protein-2 (Na-ASP-2). The N-terminal loop is connected to alpha helix 2 via a disulfide bond previously observed in Na-ASP-2. HpVAL-4 has a central cavity that is more similar to the N-terminal CAP domain of the two CAP Na-ASP-1 from Necator americanus. Unlike Na-ASP-2, mammalian CRISP, and the C-terminal CAP domain of Na-ASP-1, the large central cavity of HpVAL-4 lacks the two histidines required to coordinate divalent cations. HpVAL-4 has both palmitate-binding and sterol-binding cavities and is able to complement the in vivo sterol export phenotype of yeast mutants lacking their endogenous CAP proteins. More studies are required to determine endogenous binding partners of HpVAL-4 and unravel the possible impact of sterol binding on immune-modulatory functions.

Emerging Insights into the Functions of Pathogenesis-Related Protein 1

The members of the pathogenesis-related protein 1 (PR-1) family are among the most abundantly produced proteins in plants on pathogen attack, and PR-1 gene expression has long been used as a marker for salicylic acid-mediated disease resistance. However, despite considerable interest over several decades, their requirement and role in plant defence remains poorly understood. Recent reports have emerged demonstrating that PR-1 proteins possess sterol-binding activity, harbour an embedded defence signalling peptide, and are targeted by plant pathogens during host infection. These studies have re-energised the field and provided long-awaited insights into a possible PR-1 function. Here we review the current status of PR-1 proteins and discuss how these recent advances shed light on putative roles for these enigmatic proteins.

Structural insights into the interaction of the conserved mammalian proteins GAPR-1 and Beclin 1, a key autophagy protein

Mammalian Golgi-associated plant pathogenesis-related protein 1 (GAPR-1) is a negative autophagy regulator that binds Beclin 1, a key component of the autophagosome nucleation complex. Beclin 1 residues 267-284 are required for binding GAPR-1. Here, sequence analyses, structural modeling, mutagenesis combined with pull-down assays, X-ray crystal structure determination and small-angle X-ray scattering were used to investigate the Beclin 1-GAPR-1 interaction. Five conserved residues line an equatorial GAPR-1 surface groove that is large enough to bind a peptide. A model of a peptide comprising Beclin 1 residues 267-284 docked onto GAPR-1, built using the CABS-dock server, indicates that this peptide binds to this GAPR-1 groove. Mutation of the five conserved residues lining this groove, H54A/E86A/G102K/H103A/N138G, abrogates Beclin 1 binding. The 1.27 Å resolution X-ray crystal structure of this pentad mutant GAPR-1 was determined. Comparison with the wild-type (WT) GAPR-1 structure shows that the equatorial groove of the pentad mutant is shallower and more positively charged, and therefore may not efficiently bind Beclin 1 residues 267-284, which include many hydrophobic residues. Both WT and pentad mutant GAPR-1 crystallize as dimers, and in each case the equatorial groove of one subunit is partially occluded by the other subunit, indicating that dimeric GAPR-1 is unlikely to bind Beclin 1. SAXS analysis of WT and pentad mutant GAPR-1 indicates that in solution the WT forms monomers, while the pentad mutant is primarily dimeric. Thus, changes in the structure of the equatorial groove combined with the improved dimerization of pentad mutant GAPR-1 are likely to abrogate binding to Beclin 1.

Crystal Structure of MpPR-1i, a SCP/TAPS protein from Moniliophthora perniciosa, the fungus that causes Witches' Broom Disease of Cacao

The pathogenic fungi Moniliophthora perniciosa causes Witches’ Broom Disease (WBD) of cacao. The structure of MpPR-1i, a protein expressed by M. perniciosa when it infects cacao, are presented. This is the first reported de novo structure determined by single-wavelength anomalous dispersion phasing upon soaking with selenourea. Each monomer has flexible loop regions linking the core alpha-beta-alpha sandwich topology that comprise ~50% of the structure, making it difficult to generate an accurate homology model of the protein. MpPR-1i is monomeric in solution but is packed as a high ~70% solvent content, crystallographic heptamer. The greatest conformational flexibility between monomers is found in loops exposed to the solvent channel that connect the two longest strands. MpPR-1i lacks the conserved CAP tetrad and is incapable of binding divalent cations. MpPR-1i has the ability to bind lipids, which may have roles in its infection of cacao. These lipids likely bind in the palmitate binding cavity as observed in tablysin-15, since MpPR-1i binds palmitate with comparable affinity as tablysin-15. Further studies are required to clarify the possible roles and underlying mechanisms of neutral lipid binding, as well as their effects on the pathogenesis of M. perniciosa so as to develop new interventions for WBD.

Genomic profiling of invasive melanoma cell lines by array comparative genomic hybridization

Malignant melanoma is one of the most aggressive human cancers. Invasion of cells is the first step in metastasis, resulting in cell migration through tissue compartments. We aimed to evaluate genomic alterations specifically associated with the invasive characteristics of melanoma cells. Matrigel invasion assays were used to determine the invasive properties of cell lines that originated from primary melanomas. Array comparative genomic hybridization analyses were carried out to define the chromosome copy number alterations (CNAs). Several recurrent CNAs were identified by array comparative genomic hybridization that affected melanoma-related genes. Invasive primary cell lines showed high frequencies of CNAs, including the loss of 7q and gain of 12q chromosomal regions targeting PTPN12, ADAM22, FZD1, TFPI2, GNG11, COL1A2, SMURF1, VGF, RELN and GLIPR1 genes. Gain of the GDNF (5p13.1), GPAA1, PLEC and SHARPIN (8q24.3) genes was significantly more frequent in invasive cell lines compared with the noninvasive ones. Importantly, copy number gains of these genes were also found in cell lines that originated from metastases, suggesting their role in melanoma metastasis formation. The present study describes genomic differences between invasive and noninvasive melanoma cell lines that may contribute toward the aggressive phenotype of human melanoma cells.

Structural and functional characterization of the CAP domain of pathogen-related yeast 1 (Pry1) protein

The production, crystal structure, and functional characterization of the C-terminal cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domain of pathogen-related yeast protein-1 (Pry1) from Saccharomyces cerevisiae is presented. The CAP domain of Pry1 (Pry1CAP) is functional in vivo as its expression restores cholesterol export to yeast mutants lacking endogenous Pry1 and Pry2. Recombinant Pry1CAP forms dimers in solution, is sufficient for in vitro cholesterol binding, and has comparable binding properties as full-length Pry1. Two crystal structures of Pry1CAP are reported, one with Mg²⁺ coordinated to the conserved CAP tetrad (His208, Glu215, Glu233 and His250) in spacegroup I4₁ and the other without divalent cations in spacegroup P6₁22. The latter structure contains four 1,4-dioxane molecules from the crystallization solution, one of which sits in the cholesterol binding site. Both structures reveal that the divalent cation and cholesterol binding sites are connected upon dimerization, providing a structural basis for the observed Mg²⁺-dependent sterol binding by Pry1.

Identification of novel CAP superfamily protein members of Echinococcus granulosus protoscoleces

Echinoccocus granulosus is the causative agent of Cyst Echinococcosis, a zoonotic infection affecting humans and livestock representing a public health and an economic burden for several countries. Despite decades of investigation an effective vaccine still remains to be found. Parasitic cysteine-rich secretory proteins, antigen 5 and pathogenesis-related 1 proteins (CAPs) have been proposed as vaccine candidates against helmith's infection. In this work we have identified two novel proteins of this superfamily expressed at the protoescoleces larval stage named EgVAL1 and EgVAL2. The open reading frame sequences were deduced. The aminoacidic sequence was analyzed and confronted against already known vertebrate' and helminth's proteins sequences in order to infer putative functions. Immunolocalization studies were also performed. The obtained data supported by immunolocalization studies and homology models suggest that these proteins could be involved in protease activity inhibition.

The structure of hookworm platelet inhibitor (HPI), a CAP superfamily member from Ancylostoma caninum

Secreted protein components of hookworm species include a number of representatives of the cysteine-rich/antigen 5/pathogenesis-related 1 (CAP) protein family known as Ancylostoma-secreted proteins (ASPs). Some of these have been considered as candidate antigens for the development of vaccines against hookworms. The functions of most CAP superfamily members are poorly understood, but one form, the hookworm platelet inhibitor (HPI), has been isolated as a putative antagonist of the platelet integrins αIIbβ3 and α2β1. Here, the crystal structure of HPI is described and its structural features are examined in relation to its possible function. The HPI structure is similar to those of other ASPs and shows incomplete conservation of the sequence motifs CAP1 and CAP2 that are considered to be diagnostic of CAP superfamily members. The asymmetric unit of the HPI crystal contains a dimer with an extensive interaction interface, but chromatographic measurements indicate that it is primarily monomeric in solution. In the dimeric structure, the putative active-site cleft areas from both monomers are united into a single negatively charged depression. A potential Lys-Gly-Asp disintegrin-like motif was identified in the sequence of HPI, but is not positioned at the apex of a tight turn, making it unlikely that it interacts with the integrin. Recombinant HPI produced in Escherichia coli was found not to inhibit the adhesion of human platelets to collagen or fibrinogen, despite having a native structure as shown by X-ray diffraction. This result corroborates previous analyses of recombinant HPI and suggests that it might require post-translational modification or have a different biological function.

A dimeric PR-1-type pathogenesis-related protein interacts with ToxA and potentially mediates ToxA-induced necrosis in sensitive wheat

A dimeric PR-1-type pathogenesis-related protein (PR-1-5), recently identified in wheat, was found to interact with Stagonospora nodorum ToxA in both yeast two-hybrid and co-immunoprecipitation assays. Site-specific mutational analyses revealed that the RGD motif of ToxA is not targeted by PR-1-5, whereas two surface-exposed asparagine residues are essential for the interaction: the N102 residue of the turning loop between β2 and β3 in ToxA and the N141 residue of the turning loop between βC and βD in PR-1-5. Recombinant PR-1-5 and ToxA mutant proteins carrying alanine substitutions at the interacting sites were expressed in Pichia pastoris, together with the wild-type proteins. Native polyacrylamide gel electrophoresis (PAGE) confirmed that the PR-1-5-N141A mutant retains the ability to form dimers. Plant assays indicated that the ToxA-N102A mutant fails to induce necrosis, whereas the PR-1-5-N141A mutant is impaired in the 'necrosis-promoting' activity shown by the wild-type PR-1-5 when co-infiltrated with ToxA in sensitive wheat. Reverse transcriptase-polymerase chain reaction and Western blot analyses revealed that the native PR-1-5 protein is differentially expressed between ToxA-sensitive and ToxA-insensitive wheat lines in response to ToxA treatment. These results suggest that PR-1-5 is a potential target of ToxA and the site-specific interaction between PR-1-5 and ToxA may mediate ToxA-induced necrosis in sensitive wheat.

Schistosoma mansoni venom allergen-like protein 4 (SmVAL4) is a novel lipid-binding SCP/TAPS protein that lacks the prototypical CAP motifs

Schistosomiasis is a parasitic disease that affects over 200 million people. Vaccine candidates have been identified, including Schistosoma mansoni venom allergen-like proteins (SmVALs) from the SCP/TAPS (sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7) superfamily. The first SmVAL structure, SmVAL4, was refined to a resolution limit of 2.16 Å. SmVAL4 has a unique structure that could not be predicted from homologous structures, with longer loops and an unusual C-terminal extension. SmVAL4 has the characteristic α/β-sandwich and central SCP/TAPS cavity. Furthermore, SmVAL4 has only one of the signature CAP cavity tetrad amino-acid residues and is missing the histidines that coordinate divalent cations such as Zn(2+) in other SCP/TAPS proteins. SmVAL4 has a cavity between α-helices 1 and 4 that was observed to bind lipids in tablysin-15, suggesting the ability to bind lipids. Subsequently, SmVAL4 was shown to bind cholesterol in vitro. Additionally, SmVAL4 was shown to complement the in vivo sterol-export phenotype of yeast mutants lacking their endogenous CAP proteins. Expression of SmVAL4 in yeast cells lacking endogenous CAP function restores the block in sterol export. These studies suggest an evolutionarily conserved lipid-binding function shared by CAP proteins such as SmVAL4 and yeast CAP proteins such as Pry1.

Probing the equatorial groove of the hookworm protein and vaccine candidate antigen, Na-ASP-2

Hookworm activation-associated secreted proteins can be structurally classified into at least three different groups. The hallmark feature of Group 1 activation-associated secreted proteins is a prominent equatorial groove, which is inferred to form a ligand binding site. Furthermore, a conserved tandem histidine motif is located in the centre of the groove and believed to provide or support a yet to be determined catalytic activity. Here, we report three-dimensional crystal structures of Na-ASP-2, an L3-secreted activation-associated secreted protein from the human hookworm Necator americanus, which demonstrate transition metal binding ability of the conserved tandem histidine motif. We further identified moderate phosphohydrolase activity of recombinant Na-ASP-2, which relates to the tandem histidine motif. By panning a random 12-mer peptide phage library, we identified a peptide with high similarity to the human calcium-activated potassium channel SK3, and confirm binding of the synthetic peptide to recombinant Na-ASP-2 by differential scanning fluorimetry. Potential binding modes of the peptide to Na-ASP-2 were studied by molecular dynamics simulations which clearly identify a preferred topology of the Na-ASP-2:SK3 peptide complex.

Variable Expression of GLIPR1 Correlates with Invasive Potential in Melanoma Cells

GLI pathogenesis-related 1 (GLIPR1) was previously identified as an epigenetically regulated tumor suppressor in prostate cancer and, conversely, an oncoprotein in glioma. More recently, GLIPR1 was shown to be differentially expressed in other cancers including ovarian, acute myeloid leukemia, and Wilms' tumor. Here we investigated GLIPR1 expression in metastatic melanoma cell lines and tissue. GLIPR1 was variably expressed in metastatic melanoma cells, and transcript levels correlated with degree of GLIPR1 promoter methylation in vitro. Elevated GLIPR1 levels were correlated with increased invasive potential, and siRNA-mediated knockdown of GLIPR1 expression resulted in reduced cell migration and proliferation in vitro. Immunohistochemical studies of melanoma tissue microarrays showed moderate to high staining for GLIPR1 in 50% of specimens analyzed. GLIPR1 staining was observed in normal skin in merocrine sweat glands, sebaceous glands, and hair follicles within the dermis.

Structure of protein having inhibitory disintegrin and leukotriene scavenging functions contained in single domain

The antihemostatic/antiangiogenic protein tablysin-15 is a member of the CAP (cysteine-rich secretory, antigen 5, and pathogenesis-related 1 protein) superfamily and has been shown to bind the integrins α(IIb)β(3) and α(V)β(3) by means of an Arg-Gly-Asp (RGD) tripeptide sequence. Here we describe the x-ray crystal structure of tablysin-15 and show that the RGD motif is located in a novel structural context. The motif itself is contained in a type II β-turn structure that is similar in its conformation to the RGD sequence of the cyclic pentapeptide cilengitide when bound to integrin α(V)β(3). The CAP domain also contains a hydrophobic channel that appears to bind a fatty acid molecule in the crystal structure after purification from Escherichia coli. After delipidation of the protein, tablysin-15 was found to bind proinflammatory cysteinyl leukotrienes with submicromolar affinities. The structure of the leukotriene E(4)-tablysin-15 complex shows that the ligand binds with the nonfunctionalized end of the fatty acid chain buried in the hydrophobic pocket, whereas the carboxylate end of the ligand binds forms hydrogen bond/salt bridge interactions with polar side chains at the channel entrance. Therefore, tablysin-15 functions as an inhibitor of integrin function and as an anti-inflammatory scavenger of eicosanoids.