The AVIT protein family. Secreted cysteine-rich vertebrate proteins with diverse functions

The proteotranscriptomic characterization of venom in the white seafan Eunicella singularis elucidates the evolution of Octocorallia arsenal

All the members of the phylum Cnidaria are characterized by the production of venom in specialized structures, the nematocysts. Venom of jellyfish (Medusozoa) and sea anemones (Anthozoa) has been investigated since the 1970s, revealing a remarkable molecular diversity. Specifically, sea anemones harbour a rich repertoire of neurotoxic peptides, some of which have been developed in drug leads. However, venoms of the vast majority of Anthozoa species remain uncharacterized, particularly in the class Octocorallia. To fill this gap, we applied a proteo-transcriptomic approach to investigate venom composition in Eunicella singularis, a gorgonian species common in Mediterranean hard-bottom benthic communities. Our results highlighted the peculiarities of the venom of E. singularis with respect to sea anemones, which is reflected in the presence of several toxins with novel folds, worthy of functional characterization. A comparative genomic survey across the octocoral radiation allowed us to generalize these findings and provided insights into the evolutionary history, molecular diversification patterns and putative adaptive roles of venom toxins. A comparison of whole-body and nematocyst proteomes revealed the presence of different cytolytic toxins inside and outside the nematocysts. Two instances of differential maturation patterns of toxin precursors were also identified, highlighting the intricate regulatory pathways underlying toxin expression.

MRAP2 Inhibits β-Arrestin-2 Recruitment to the Prokineticin Receptor 2

Melanocortin receptor accessory protein 2 (MRAP2) is a membrane protein that binds multiple G protein-coupled receptors (GPCRs) involved in the control of energy homeostasis, including prokineticin receptors. These GPCRs are expressed both centrally and peripherally, and their endogenous ligands are prokineticin 1 (PK1) and prokineticin 2 (PK2). PKRs couple all G-protein subtypes, such as Gαq/11, Gαs, and Gαi, and recruit β-arrestins upon PK2 stimulation, although the interaction between PKR2 and β-arrestins does not trigger receptor internalisation. MRAP2 inhibits the anorexigenic effect of PK2 by binding PKR1 and PKR2. The aim of this work was to elucidate the role of MRAP2 in modulating PKR2-induced β-arrestin-2 recruitment and β-arrestin-mediated signalling. This study could allow the identification of new specific targets for potential new drugs useful for the treatment of the various pathologies correlated with prokineticin, in particular, obesity.

The Prokineticin System in Inflammatory Bowel Diseases: A Clinical and Preclinical Overview

Inflammatory bowel disease (IBD) includes Crohn's disease (CD) and ulcerative colitis (UC), which are characterized by chronic inflammation of the gastrointestinal (GI) tract. IBDs clinical manifestations are heterogeneous and characterized by a chronic relapsing-remitting course. Typical gastrointestinal signs and symptoms include diarrhea, GI bleeding, weight loss, and abdominal pain. Moreover, the presence of pain often manifests in the remitting disease phase. As a result, patients report a further reduction in life quality. Despite the scientific advances implemented in the last two decades and the therapies aimed at inducing or maintaining IBDs in a remissive condition, to date, their pathophysiology still remains unknown. In this scenario, the importance of identifying a common and effective therapeutic target for both digestive symptoms and pain remains a priority. Recent clinical and preclinical studies have reported the prokineticin system (PKS) as an emerging therapeutic target for IBDs. PKS alterations are likely to play a role in IBDs at multiple levels, such as in intestinal motility, local inflammation, ulceration processes, localized abdominal and visceral pain, as well as central nervous system sensitization, leading to the development of chronic and widespread pain. This narrative review summarized the evidence about the involvement of the PKS in IBD and discussed its potential as a druggable target.

Therapeutic Potential of Targeting Prokineticin Receptors in Diseases

The prokineticins (PKs) were discovered approximately 20 years ago as small peptides inducing gut contractility. Today, they are established as angiogenic, anorectic, and proinflammatory cytokines, chemokines, hormones, and neuropeptides involved in variety of physiologic and pathophysiological pathways. Their altered expression or mutations implicated in several diseases make them a potential biomarker. Their G-protein coupled receptors, PKR1 and PKR2, have divergent roles that can be therapeutic target for treatment of cardiovascular, metabolic, and neural diseases as well as pain and cancer. This article reviews and summarizes our current knowledge of PK family functions from development of heart and brain to regulation of homeostasis in health and diseases. Finally, the review summarizes the established roles of the endogenous peptides, synthetic peptides and the selective ligands of PKR1 and PKR2, and nonpeptide orthostatic and allosteric modulator of the receptors in preclinical disease models. The present review emphasizes the ambiguous aspects and gaps in our knowledge of functions of PKR ligands and elucidates future perspectives for PK research. SIGNIFICANCE STATEMENT: This review provides an in-depth view of the prokineticin family and PK receptors that can be active without their endogenous ligand and exhibits "constitutive" activity in diseases. Their non- peptide ligands display promising effects in several preclinical disease models. PKs can be the diagnostic biomarker of several diseases. A thorough understanding of the role of prokineticin family and their receptor types in health and diseases is critical to develop novel therapeutic strategies with safety concerns.

Clinical Characteristics and Genetic Analyses of Patients with Idiopathic Hypogonadotropic Hypogonadism

Objective

Idiopathic hypogonadotropic hypogonadism (IHH) is classified into two groups-Kalman syndrome and normosmic IHH (nIHH). Half of all cases can be explained by mutations in >50 genes. Targeted gene panel testing with nexrt generation sequencing (NGS) is required for patients without typical phenotypic findings. The aim was to determine the genetic etiologies of patients with IHH using NGS, including 54 IHH-associated genes, and to present protein homology modeling and protein stability analyzes of the detected variations.

Methods

Clinical and demographic data of 16 patients (eight female), aged between 11.6-17.8 years, from different families were assessed. All patients were followed up for a diagnosis of nIHH, had normal cranial imaging, were without anterior pituitary hormone deficiency other than gonadotropins, had no sex chromosome anomaly, had no additional disease, and underwent genetic analysis with NGS between the years 2008-2021. Rare variants were classified according to the variant interpretation framework of the American College of Medical Genetics and Genomics (ACMG)/Association for Molecular Pathology. Changes in protein structure caused by variations were modeled using RoseTTAFold and changes in protein stability resulting from variation were analyzed.

Results

Half of the 16 had no detectable variation. Three (18.75%) had a homozygous (pathogenic) variant in the GNRHR gene, one (6.25%) had a compound heterozygous [likely pathogenic-variants of uncertain significance (VUS)] variant in PROK2 and four (25%) each had a heterozygous (VUS) variant in HESX1, FGF8, FLRT3 and DMXL2. Protein models showed that variants interpreted as VUS according to ACMG could account for the clinical IHH.

Conclusion

The frequency of variation detection was similar to the literature. Modelling showed that the variant in five different genes, interpreted as VUS according to ACMG, could explain the clinical IHH.

Prokineticin 1 is a novel factor regulating porcine corpus luteum function

Prokineticin 1 (PROK1) is a pleiotropic factor secreted by endocrine glands; however, its role has not been studied in the corpus luteum (CL) during pregnancy in any species. The present study aimed to investigate the contribution of PROK1 in regulating processes related to porcine CL function and regression: steroidogenesis, luteal cell apoptosis and viability, and angiogenesis. The luteal expression of PROK1 was greater on Days 12 and 14 of pregnancy compared to Day 9. PROK1 protein expression during pregnancy increased gradually and peaked on Day 14, when it was also significantly higher than that on Day 14 of the estrous cycle. Prokineticin receptor 1 (PROKR1) mRNA abundance increased on Days 12 and 14 of pregnancy, whereas PROKR2 elevated on Day 14 of the estrous cycle. PROK1, acting via PROKR1, stimulated the expression of genes involved in progesterone synthesis, as well as progesterone secretion by luteal tissue. PROK1-PROKR1 signaling reduced apoptosis and increased the viability of luteal cells. PROK1 acting through PROKR1 stimulated angiogenesis by increasing capillary-like structure formation by luteal endothelial cells and elevating angiogenin gene expression and VEGFA secretion by luteal tissue. Our results indicate that PROK1 regulates processes vital for maintaining luteal function during early pregnancy and the mid-luteal phase.

Spiders' digestive system as a source of trypsin inhibitors: functional activity of a member of atracotoxin structural family

Spiders are important predators of insects and their venoms play an essential role in prey capture. Spider venoms have several potential applications as pharmaceutical compounds and insecticides. However, transcriptomic and proteomic analyses of the digestive system (DS) of spiders show that DS is also a rich source of new peptidase inhibitor molecules. Biochemical, transcriptomic and proteomic data of crude DS extracts show the presence of molecules with peptidase inhibitor potential in the spider Nephilingis cruentata. Therefore, the aims of this work were to isolate and characterize molecules with trypsin inhibitory activity. The DS of fasting adult females was homogenized under acidic conditions and subjected to heat treatment. After that, samples were submitted to ion exchange batch and high-performance reverse-phase chromatography. The fractions with trypsin inhibitory activity were confirmed by mass spectrometry, identifying six molecules with inhibitory potential. The inhibitor NcTI (Nephilingis cruentata trypsin inhibitor) was kinetically characterized, showing a K_D value of 30.25 nM ± 8.13. Analysis of the tertiary structure by molecular modeling using Alpha-Fold2 indicates that the inhibitor NcTI structurally belongs to the MIT1-like atracotoxin family. This is the first time that a serine peptidase inhibitory function is attributed to this structural family and the inhibitor reactive site residue is identified. Sequence analysis indicates that these molecules may be present in the DS of other spiders and could be associated to the inactivation of prey trypsin (serine peptidase) ingested by the spiders.

Non-Peptide Agonists and Antagonists of the Prokineticin Receptors

The prokineticin family comprises a group of secreted peptides that can be classified as chemokines based on their structural features and chemotactic and immunomodulatory functions. Prokineticins (PKs) bind with high affinity to two G protein-coupled receptors (GPCRs). Prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2) are involved in a variety of physiological functions such as angiogenesis and neurogenesis, hematopoiesis, the control of hypothalamic hormone secretion, the regulation of circadian rhythm and the modulation of complex behaviors such as feeding and drinking. Dysregulation of the system leads to an inflammatory process that is the substrate for many pathological conditions such as cancer, pain, neuroinflammation and neurodegenerative diseases such as Alzheimer's and Parkinson's disease. The use of PKR's antagonists reduces PK2/PKRs upregulation triggered by various inflammatory processes, suggesting that a pharmacological blockade of PKRs may be a successful strategy to treat inflammatory/neuroinflammatory diseases, at least in rodents. Under certain circumstances, the PK system exhibits protective/neuroprotective effects, so PKR agonists have also been developed to modulate the prokineticin system.

Identification and Characterization of a New Splicing Variant of Prokineticin 2

Prokineticin 2 (PROK2) is a secreted bioactive peptide that regulates a variety of biological responses via two GPCRs, the prokineticin receptors (PROKRs). The aim of this study was to characterize a new alternatively spliced product of the prok2 gene consisting of four exons. The 40-amino acid peptide, designated PROK2C, is encoded by exon 1 and exon 4, and its expression was detected in the hippocampus and spinal cord of mice. PROK2C was expressed in a heterologous system, Pichia pastoris, and its binding specificity to the amino-terminal regions of PROKR1 and PROKR2 was investigated by GST pull-down experiments. In addition, the introduction of the unnatural amino acid p-benzoyl-L-phenylalanine using amber codon suppression technology demonstrated the role of tryptophan at position 212 of PROKR2 for PROK2C binding by photoactivatable cross-linking. The functional significance of this new isoform was determined in vivo by nociceptive experiments, which showed that PROK2C elicits strong sensitization of peripheral nociceptors to painful stimuli. In order to analyze the induction of PROK2C signal transduction, STAT3 and ERK phosphorylation levels were determined in mammalian CHO cells expressing PROKR1 and PROKR2. Our data show by in vivo and in vitro experiments that PROK2C can bind and activate both prokineticin receptors.

Prokineticin-Receptor Network: Mechanisms of Regulation

Prokineticins are a new class of chemokine-like peptides that bind their G protein-coupled receptors, PKR1 and PKR2, and promote chemotaxis and the production of pro-inflammatory cytokines following tissue injury or infection. This review summarizes the major cellular and biochemical mechanisms of prokineticins pathway regulation that, like other chemokines, include: genetic polymorphisms; mRNA splice modulation; expression regulation at transcriptional and post-transcriptional levels; prokineticins interactions with cell-surface glycosaminoglycans; PKRs degradation, localization, post-translational modifications and oligomerization; alternative signaling responses; binding to pharmacological inhibitors. Understanding these mechanisms, which together exert substantial biochemical control and greatly enhance the complexity of the prokineticin-receptor network, leads to novel opportunities for therapeutic intervention. In this way, besides targeting prokineticins or their receptors directly, it could be possible to indirectly influence their activity by modulating their expression and localization or blocking the downstream signaling pathways.

Biphasic (5-2%) oxygen concentration strategy significantly improves the usable blastocyst and cumulative live birth rates in in vitro fertilization

Oxygen (O₂) concentration is approximately 5% in the fallopian tube and 2% in the uterus in humans. A "back to nature" approach could increase in vitro fertilization (IVF) outcomes. This hypothesis was tested in this monocentric observational retrospective study that included 120 couples who underwent two IVF cycles between 2014 and 2019. Embryos were cultured at 5% from day 0 (D0) to D5/6 (monophasic O₂ concentration strategy) in the first IVF cycle, and at 5% O₂ from D0 to D3 and 2% O₂ from D3 to D5/6 (biphasic O₂ concentration strategy) in the second IVF cycle. The total and usable blastocyst rates (44.4% vs. 54.8%, p = 0.049 and 21.8% vs. 32.8%, p = 0.002, respectively) and the cumulative live birth rate (17.9% vs. 44.1%, p = 0.027) were significantly higher with the biphasic (5%-2%) O₂ concentration strategy. Whole transcriptome analysis of blastocysts donated for research identified 707 RNAs that were differentially expressed in function of the O₂ strategy (fold-change > 2, p value < 0.05). These genes are mainly involved in embryo development, DNA repair, embryonic stem cell pluripotency, and implantation potential. The biphasic (5-2%) O₂ concentration strategy for preimplantation embryo culture could increase the "take home baby rate", thus improving IVF cost-effectiveness and infertility management.

Versatile Role of Prokineticins and Prokineticin Receptors in Neuroinflammation

Prokineticins are a new class of chemokine-like peptides involved in a wide range of biological and pathological activities. In particular, prokineticin 2 (PK2), prokineticin receptor 1 (PKR1) and prokineticin receptor 2 (PKR2) play a central role in modulating neuroinflammatory processes. PK2 and PKRs, which are physiologically expressed at very low levels, are strongly upregulated during inflammation and regulate neuronal-glial interaction. PKR2 is mainly overexpressed in neurons, whereas PKR1 and PK2 are mainly overexpressed in astrocytes. Once PK2 is released in inflamed tissue, it is involved in both innate and adaptive responses: it triggers macrophage recruitment, production of pro-inflammatory cytokines, and reduction of anti-inflammatory cytokines. Moreover, it modulates the function of T cells through the activation of PKR1 and directs them towards a pro-inflammatory Th1 phenotype. Since the prokineticin system appears to be upregulated following a series of pathological insults leading to neuroinflammation, we will focus here on the involvement of PK2 and PKRs in those pathologies that have a strong underlying inflammatory component, such as: inflammatory and neuropathic pain, Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, obesity, diabetes, and gastrointestinal inflammation.

Prokineticin 2 overexpression induces spermatocyte apoptosis in varicocele in rats

Varicocele is one of the most important causes of male infertility, as this condition leads to a decline in sperm quality. It is generally believed that the presence of varicocele induces an increase in reactive oxygen species levels, leading to oxidative stress and sperm apoptosis; however, the specific pathogenic mechanisms affecting spermatogenesis remain elusive. Prokineticin 2 (PK2), a secretory protein, is associated with multiple biological processes, including cell migration, proliferation, and apoptosis. In the testis, PK2 is expressed in spermatocytes under normal physiological conditions. To investigate the role of PK2 in varicocele, a rat varicocele model was established to locate and quantify the expression of PK2 and its receptor, prokineticin receptor 1 (PKR1), by immunohistochemistry and quantitative real-time PCR assays (qPCR). Moreover, H₂O₂ was applied to mimic the oxidative stress state of varicocele through coculturing with a spermatocyte-derived cell line (GC-2) in vitro, and the apoptosis rate was detected by flow cytometry. Here, we illustrated that the expression levels of PK2 and PKR1 were upregulated in the spermatocytes of the rat model. Administration of H₂O₂ stimulated the overexpression of PK2 in GC-2. Transfection of recombinant pCMV-HA-PK2 into GC-2 cells promoted apoptosis by upregulating cleaved-caspase-3, caspase-8, and B cell lymphoma 2-associated X; downregulating B cell lymphoma 2; and promoting the accumulation of intracellular calcium. Overall, we revealed that the varicocele-induced oxidative stress stimulated the overexpression of PK2, leading to apoptosis of spermatocytes. Our study provides new insight into the mechanisms underlying oxidative stress-associated male infertility and suggests a novel therapeutic target for male infertility.

Pleiotropic effects of prokineticin 2 in the control of energy metabolism

Prokineticins are family of small proteins involved in many important biological processes including food intake and control of energy balance. The prokineticin 2 (PROK2) is expressed in several peripheral tissues and areas in the central nervous system. PROK2 activates G protein-coupled receptors, namely, prokineticin receptor 1 (PROKR1) and prokineticin receptor 2 (PROKR2). Preclinical models exhibiting disturbances of the PROK2 pathway (at the level of PROK2 or its receptors) are characterized by changes in food intake, feeding behavior and insulin sensitivity related to a dysfunction of the energy balance control. In Humans, mutations of PROK2 and PROKR2 genes are associated to the Kallmann syndrome (KS) that affects both the hormonal reproductive axis and the sense of smell and may also lead to obesity. Moreover, plasma PROK2 concentration has been correlated with various cardiometabolic risk factors and type 2 diabetes (T2D). The present review summarizes knowledge on PROK2 structure, signaling and function focusing on its role in control of food intake and energy homeostasis.

Targeting GPCRs Against Cardiotoxicity Induced by Anticancer Treatments

Novel anticancer medicines, including targeted therapies and immune checkpoint inhibitors, have greatly improved the management of cancers. However, both conventional and new anticancer treatments induce cardiac adverse effects, which remain a critical issue in clinic. Cardiotoxicity induced by anti-cancer treatments compromise vasospastic and thromboembolic ischemia, dysrhythmia, hypertension, myocarditis, and cardiac dysfunction that can result in heart failure. Importantly, none of the strategies to prevent cardiotoxicity from anticancer therapies is completely safe and satisfactory. Certain clinically used cardioprotective drugs can even contribute to cancer induction. Since G protein coupled receptors (GPCRs) are target of forty percent of clinically used drugs, here we discuss the newly identified cardioprotective agents that bind GPCRs of adrenalin, adenosine, melatonin, ghrelin, galanin, apelin, prokineticin and cannabidiol. We hope to provoke further drug development studies considering these GPCRs as potential targets to be translated to treatment of human heart failure induced by anticancer drugs.

Spider Venom: Components, Modes of Action, and Novel Strategies in Transcriptomic and Proteomic Analyses

This review gives an overview on the development of research on spider venoms with a focus on structure and function of venom components and techniques of analysis. Major venom component groups are small molecular mass compounds, antimicrobial (also called cytolytic, or cationic) peptides (only in some spider families), cysteine-rich (neurotoxic) peptides, and enzymes and proteins. Cysteine-rich peptides are reviewed with respect to various structural motifs, their targets (ion channels, membrane receptors), nomenclature, and molecular binding. We further describe the latest findings concerning the maturation of antimicrobial, and cysteine-rich peptides that are in most known cases expressed as propeptide-containing precursors. Today, venom research, increasingly employs transcriptomic and mass spectrometric techniques. Pros and cons of venom gland transcriptome analysis with Sanger, 454, and Illumina sequencing are discussed and an overview on so far published transcriptome studies is given. In this respect, we also discuss the only recently described cross contamination arising from multiplexing in Illumina sequencing and its possible impacts on venom studies. High throughput mass spectrometric analysis of venom proteomes (bottom-up, top-down) are reviewed.

Chemokines in Alzheimer's Disease: New Insights Into Prokineticins, Chemokine-Like Proteins

Alzheimer’s disease is the most common neurodegenerative disorder characterized by the presence of β-amyloid aggregates deposited as senile plaques and by the presence of neurofibrillary tangles of tau protein. To date, there is a broad consensus on the idea that neuroinflammation is one of the most important component in Alzheimer’s disease pathogenesis. Chemokines and their receptors, beside the well-known role in the immune system, are widely expressed in the nervous system, where they play a significant role in the neuroinflammatory processes. Prokineticins are a new family of chemokine-like molecules involved in numerous physiological and pathological processes including immunity, pain, inflammation, and neuroinflammation. Prokineticin 2 (PROK2) and its receptors PKR1 and PKR2 are widely expressed in the central nervous system in both neuronal and glial cells. In Alzheimer’s disease, PROK2 sustains the neuroinflammatory condition and contributes to neurotoxicity, since its expression is strongly upregulated by amyloid-β peptide and reversed by the PKR antagonist PC1. This review aims to summarize the current knowledge on the neurotoxic and/or neuroprotective function of chemokines in Alzheimer’s disease, focusing on the prokineticin system: it represents a new field of investigation that can stimulate the research of innovative pharmacotherapeutic strategies.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) and its receptor PROKR2 are associated to human colorectal cancer progression and peritoneal carcinomatosis

BACKGROUND

The highest risk factor for mortality among malignant tumors is metastasis. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor which biological activity is mediated via two G protein-coupled receptors, prokineticin receptor1 (PROKR1) and PROKR2. Recent studies suggested that EG-VEGF expression is deregulated in multiple cancers including colorectal cancer (CRC).

METHODS

Using distinctive CRC and peritoneal carcinomatosis (PC) cohorts and a corresponding control cohort, we determined the circulating levels of EG-VEGF and its in situ expression, and that of its related receptors.

RESULTS

Circulating EG-VEGF levels were significantly increased in patients with metastatic PC compared to CRC and control patients (p< 0.05). Furthermore, according to clinicopathologic examinations, local EG-VEGF expression correlated with higher tumor and nodal stages (p< 0.001) of CRC. EG-VEGF and PROKR2 were highly expressed in colorectal primary lesions compared to positive controls. PROKR1 expression was lower and did not change in tumor specimens. Also, EG-VEGF and its receptor PROKR2 were differentially expressed in the colorectal primary lesions and in the control groups.

CONCLUSION

Altogether these findings suggest that EG-VEGF/receptors system might be an important actor in the CRC progression into PC and might be involved in the ability of tumor cells to invade other organs. Circulating EG-VEGF could be proposed as a prognostic marker in human CRC and its progression into PC.

A Prokineticin (PK)-like cytokine from Chinese mitten crab Eriocheir sinensis promotes the production of hemocytes via reactive oxygen species

Astakine is a cytokine-like factor containing a prokineticin domain, which directly participates in hematopoiesis and blood cell differentiation. In the present study, a novel Astakine gene was identified from Chinese mitten crab Eriocheir sinensis (designated as EsAst). The full-length cDNA of EsAst was of 1163 bp, consisting of a 5' untranslated region (UTR) of 120 bp, a 3' UTR of 656 bp, and an open reading frame (ORF) of 387 bp encoding a polypeptide of 128 amino acids. There were a signal peptide and a prokineticin domain with nine conserved cysteine residues in the deduced amino acid sequence of EsAst. EsAst shared higher similarity with Astakines from Penaeus monodon and Pacifastacus leniusculus, and it was closely clustered with the Astakine from shrimp P. monodon in the phylogenetic tree. The EsAst mRNA transcript was higher expressed in hemocytes and hepatopancreas. The relative expression level of EsAst in hemocytes was continuously increased from 1.5 to 48 h after Vibro anguillarum challenge compared that in the untreated control group. After Pichia pastoris GS115 challenge, the relative expression level of EsAst in hemocytes was also up-regulated. After rEsAst injection, ROS levels in HPT cells were also increased at 12 and 24 h, and the total hemocyte counts were also significantly increased at 6, 9, 12, and 24 h post rEsAst injection. The interference of EsAst expression with dsRNA injection could delay the recovery of hemocytes production post A. hydrophila stimulation. When mitochondrial complexes I was knock down by dsRNA, ROS levels were decreased and THCs were also decreased. Recovery of hemocyte production inducing by A. hydrophila stimulation and rEsAst injection were delayed with dsEsbc1 injection. When ROS levels were increased after RNAi of Lon protease, THCs were also increased. The expression levels of five genes (EsJNK, EsSTAT, EsPI3K, EsAKT1, EsP70S6K) involved in SAPK-JNK and mTOR signaling pathways were up-regulated at 12 and 24 h in rEsAst group and EsLon dsRNA group compared with that in EGFP dsRNA group, and were similar to the trend of ROS levels. These results collectively suggested that EsAst should be a novel Astakine to promote the production of hemocytes in a ROS-dependent way in E. sinensis.

Astakines in arthropods-phylogeny and gene structure

Astakine1 was isolated as a hematopoietic cytokine in the freshwater crayfish Pacifastacus leniusculus. In this study we detect and compare 79 sequences in GenBank, which we consider to be possible astakine orthologs, among which eleven are crustacean, sixteen are chelicerate and 52 are from insect species. Available arthropod genomes are searched for astakines, and in conclusion all astakine sequences in the current study have a similar exon containing CCXX(X), thus potentially indicating that they are homologous genes with the structure of this exon highly conserved. Two motifs, RYS and YP(N), are also conserved among the arthropod astakines. A phylogenetic analysis reveals that astakine1 and astakine2 from P. leniusculus and Procambarus clarkii are distantly related, and may have been derived from a gene duplication occurring early in crustacean evolution. Moreover, a structural comparison using the Mamba intestinal toxin (MIT1) from Dendroaspis polylepis as template indicates that the overall folds are similar in all crustacean astakines investigated.

Prokineticin Is a New Linker between Obesity and Cardiovascular Diseases

Obesity is a fast growing epidemic event worldwide. Fatness is associated with a number of comorbidities, including cardiovascular diseases (CVDs). Although obesity can be heredity in 30–70% cases, the environmental contributions also play an important role in the increasing prevalence of obesity. The relationship between development of obesity and CVD is poorly characterized. Obesity and CVD can also be resulted from a common mechanism such as metabolic, inflammatory, and neurohormonal changes. Prokineticins are defined as cytokines (immunoregulatory proteins), adipokines (adipocyte-secreted hormone), angiogenic (increasing vessel formation), or aneroxic (lowering food intake) hormones. Prokineticin-mediated signaling plays a key role in the development of obesity and CVD. Two forms of prokineticins exist in circulation and in various tissues including the brain, heart, kidney, and adipose. Prokineticins act on the two G protein-coupled receptors, namely, PKR1 and PKR2. Prokineticin-2 (PK2) via PKR1 receptor controls food intake and prevents adipose tissue expansion. The anti-adipocyte effect of PKR1 signaling is due to suppression of preadipocyte proliferation and differentiation capacity into adipocytes. PK2/PKR1 signaling promotes transcapillary passages of insulin and increases insulin sensitivity. It also plays an important role in the heart and kidney development and functions. Here, we discuss PK2 as a new adipocytokine in the association between obesity and CVD. We also highlight targeting PKR1 can be a new approach to treat obesity and CVD.

Involvement of Prokineticin 2 and Prokineticin Receptor 1 in Lipopolysaccharide-Induced Testitis in Rats

Prokineticin 2, a newly discovered proinflammatory peptide, has been amply evidenced to be involved in the occurrence and progress of local and systematical inflammation. Although the presence of Prokineticn 2 in mammal testis has been documented clearly, research targeting the involvement of prokineticin 2 in testicular pathology, especially testitis, is rather scarce. Employing a lipopolysaccharide-induced testitis rat model, we for the first time demonstrated the expression and upregulation of prokineticin 2 in orchitis at several levels. Our effort also addressed the differential expression patterns of prokineticin 2 and interleukin-1β, a key inflammation indicator, during testitis suggesting Prokineticn 2 serves more than a proinflammatory factor in the context of testitis. Given one of the cognate receptors of prokineticin 2, prokineticin receptor 1 (PKR1) was also significantly upregulated in orchitis as discussed in the current study, it is very likely that PK2/PKR1 signaling contribute to the development of inflammation-related testicular diseases.

Prokineticins in central and peripheral control of human reproduction

Prokineticin 1 (PROK1) and (PROK2), are two closely related proteins that were identified as the mammalian homologs of their two amphibian homologs, mamba intestinal toxin (MIT-1) and Bv8. PROKs activate two G-protein linked receptors (prokineticin receptor 1 and 2, PROKR1 and PROKR2). Both PROK1 and PROK2 have been found to regulate a stunning array of biological functions. In particular, PROKs stimulate gastrointestinal motility, thus accounting for their family name "prokineticins". PROK1 acts as a potent angiogenic mitogen, thus earning its other name, endocrine gland-derived vascular endothelial factor. In contrast, PROK2 signaling pathway has been shown to be a critical regulator of olfactory bulb morphogenesis and sexual maturation. During the last decade, strong evidences established the key roles of prokineticins in the control of human central and peripheral reproductive processes. PROKs act as main regulators of the physiological functions of the ovary, uterus, placenta, and testis, with marked dysfunctions in various pathological conditions such as recurrent pregnancy loss, and preeclampsia. PROKs have also been associated to the tumor development of some of these organs. In the central system, prokineticins control the migration of GnRH neurons, a key process that controls reproductive functions. Importantly, mutations in PROK2 and PROKR2 are associated to the development of Kallmann syndrome, with direct consequences on the reproductive system. This review describes the finely tuned actions of prokineticins in the control of the central and peripheral reproductive processes. Also, it discusses future research directions for the use of these cytokines as diagnostic markers for several reproductive diseases.

Molecular expression of vascular endothelial growth factor, prokineticin receptor-1 and other biomarkers in infiltrating canalicular carcinoma of the breast

Vascular endothelial growth factor (VEGF) is important in the growth and metastasis of cancer cells. In 2001, another angiogenic factor, endocrine gland-derived VEGF (EG-VEGF), was characterized and sequenced. EG-VEGF activity appears to be restricted to endothelial cells derived from endocrine glands. At the molecular level, its expression is regulated by hypoxia and steroid hormones. Although VEGF and EG-VEGF are structurally different, they function in a coordinated fashion. Since the majority of mammary tumors are hormone-dependent, it was hypothesized that EG-VEGF would be expressed in these tumors, and therefore, represent a potential target for anti-angiogenic therapy. The aim of the present study was to assess the expression of VEGF, EG-VEGF and its receptor (prokineticin receptor-1), as well as that of breast cancer resistant protein, estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2, in 50 breast samples of infiltrating canalicular carcinoma (ICC) and their correlation with tumor staging. The samples were analyzed using reverse transcription-quantitative polymerase chain reaction and immunohistochemistry. Both angiogenic growth factors were identified in all samples. However, in 90% of the samples, the expression level of VEGF was significantly higher than that of EG-VEGF (P=0.024). There was no association between the expression of VEGF, EG-VEGF or its receptor with tumor stage. In ICC, the predominant angiogenic factor expressed was VEGF. The expression level of either factor was not correlated with the tumor-node-metastasis stage. Although ICC is derived from endothelial cells, EG-VEGF expression was not the predominant angiogenic/growth factor in ICC.

Sustained Endocrine Gland-Derived Vascular Endothelial Growth Factor Levels Beyond the First Trimester of Pregnancy Display Phenotypic and Functional Changes Associated With the Pathogenesis of Pregnancy-Induced Hypertension

Pregnancy-induced hypertension diseases are classified as gestational hypertension, preeclampsia, or eclampsia. The mechanisms of their development and prediction are still to be discovered. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor secreted by the placenta during the first trimester of human pregnancy that was shown to control trophoblast invasion, to be upregulated by hypoxia, and to be abnormally elevated in pathological pregnancies complicated with preeclampsia and intrauterine growth restriction. These findings suggested that sustaining EG-VEGF levels beyond the first trimester of pregnancy may contribute to pregnancy-induced hypertension. To test this hypothesis, osmotic minipumps delivering EG-VEGF were implanted subcutaneously into gravid OF1 (Oncins France 1) mice on day 11.5 post coitus, which is equivalent to the end of the first trimester of human pregnancy. Mice were euthanized at 15.5 and 18.5 days post coitus to assess (1) litter size, placental, and fetal weights; (2) placental histology and function; (3) maternal blood pressure; (4) renal histology and function; and (5) circulating soluble fms-like tyrosine kinase 1 and soluble endoglin. Increased EG-VEGF levels caused significant defects in placental organization and function. Both increased hypoxia and decreased trophoblast invasion were observed. Treated mice had elevated circulating soluble fms-like tyrosine kinase 1 and soluble endoglin and developed gestational hypertension with dysregulated maternal kidney function. EG-VEGF effect on the kidney function was secondary to its effects on the placenta as similarly treated male mice had normal kidney functions. Altogether, these data provide a strong evidence to confirm that sustained EG-VEGF beyond the first trimester of pregnancy contributes to the development of pregnancy-induced hypertension.

Analysis of the Prokineticin 2 System in a Diurnal Rodent, the Unstriped Nile Grass Rat (Arvicanthis niloticus)

Prokineticin 2 (PK2) is a putative output molecule from the SCN. PK2 RNA levels are rhythmic in the mouse SCN, with high levels during the day, and PK2 administration suppresses nocturnal locomotor activity in rats. The authors examined the PK2 system in a diurnal rodent, Arvicanthis niloticus, to determine whether PK2 or PK2 receptors differ between diurnal and nocturnal species. The major transcript variant of A. niloticus PK2 ( AnPK2) encodes a 26-residue signal peptide followed by the presumed mature peptide of 81 residues. Within the grass rat signal sequence, polymorphic sequences and amino acid substitutions were observed relative to mouse and laboratory rats, but the hydrophobic core and cleavage site of the signal sequence were preserved. The mature PK2 peptide is identical among A. niloticus, rat, and mouse. AnPK2 mRNA is rhythmically expressed in the SCN, with peak RNAlevels occurring in the morning, preceding peaks of Per1 and Per2 as in mouse SCN. Analysis of prokineticin receptor 2 (PKR2) sequences revealed polymorphisms among the grass rats studied. PKR2 mRNAwas expressed in the SCN and paraventricular nuclei of the thalamus and hypothalamus. While further analysis is necessary, there is no clear evidence indicating that a difference in the PK2 ligand/receptor system accounts for diurnality in this rodent species. These data contribute to a growing body of evidence suggesting that the key to diurnality lies downstream of the SCN in A. niloticus.

[Relationships between venomous function and innate immune function]

Venomous function is investigated in relation to innate immune function in two cases selected from scorpion venom and serpent venom. In the first case, structural analysis of scorpion toxins and defensins reveals a close interrelation between both functions (toxic and innate immune system function). In the second case, structural and functional studies of natural inhibitors of toxic snake venom phospholipases A2 reveal homology with components of the innate immune system, leading to a similar conclusion. Although there is a clear functional distinction between neurotoxins, which act by targeting membrane ion channels, and the circulating defensins which protect the organism from pathogens, the scorpion short toxins and defensins share a common protein folding scaffold with a conserved cysteine-stabilized alpha-beta motif of three disulfide bridges linking a short alpha helix and an antiparallel beta sheet. Genomic analysis suggests that these proteins share a common ancestor (long venom toxins were separated from an early gene family which gave rise to separate short toxin and defensin families). Furthermore, a scorpion toxin has been experimentally synthetized from an insect defensin, and an antibacterial scorpion peptide, androctonin (whose structure is similar to that of a cone snail venom toxin), was shown to have a similar high affinity for the postsynaptic acetylcholine receptor of Torpedo sp. Natural inhibitors of phospholipase A2 found in the blood of snakes are associated with the resistance of venomous snakes to their own highly neurotoxic venom proteins. Three classes of phospholipases A2 inhibitors (PLI-α, PLI-β, PLI-γ) have been identified. These inhibitors display diverse structural motifs related to innate immune proteins including carbohydrate recognition domains (CRD), leucine rich repeat domains (found in Toll-like receptors) and three finger domains, which clearly differentiate them from components of the adaptive immune system. Thus, in structure, function and phylogeny, venomous function in both vertebrates and invertebrates are clearly interrelated with innate immune function.

PK2/PKR1 Signaling Regulates Bladder Function and Sensation in Rats with Cyclophosphamide-Induced Cystitis

Prokineticin 2 (PK2) is a novel chemokine-like peptide with multiple proinflammatory and nociception-related activities. This study aimed to explore the potential role of PK2 in modulating bladder activity and sensation in rats with cyclophosphamide- (CYP-) induced cystitis. Changes of PK2 and prokineticin receptors (PKRs) in normal and inflamed urinary bladders were determined at several time points (4 h, 48 h, and 8 d) after CYP treatment. Combining a nonselective antagonist of prokineticin receptors (PKRA), we further evaluated the regulatory role of PK2 in modulating bladder function and visceral pain sensation via conscious cystometry and pain behavioral scoring. PK2 and prokineticin receptor 1 (PKR1), but not prokineticin receptor 2, were detected in normal and upregulated in CYP-treated rat bladders at several levels. Immunohistochemistry staining localized PKR1 primarily in the urothelium. Blocking PKRs with PKRA showed no effect on micturition reflex activity and bladder sensation in control rats while it increased the voiding volume, prolonged voiding interval, and ameliorated visceral hyperalgesia in rats suffering from CYP-induced cystitis. In conclusion, PK2/PKR1 signaling pathway contributes to the modulation of inflammation-mediated voiding dysfunction and spontaneous visceral pain. Local blockade of PKRs may represent a novel and promising therapeutic strategy for the clinical management of inflammation-related bladder diseases.

Bv8/prokineticin 2 is involved in Aβ-induced neurotoxicity

Bv8/Prokineticin 2 (PROK2) is a bioactive peptide initially discovered as a regulator of gastrointestinal motility. Among multiple biological roles demonstrated for PROK2, it was recently established that PROK2 is an insult-inducible endangering mediator for cerebral damage. Aim of the present study was to evaluate the PROK2 and its receptors' potential involvement in amyloid beta (Aβ) neurotoxicity, a hallmark of Alzheimer's disease (AD) and various forms of traumatic brain injury (TBI). Analyzing primary cortical cultures (CNs) and cortex and hippocampus from Aβ treated rats, we found that PROK2 and its receptors PKR1 and PKR2 mRNA are up-regulated by Aβ, suggesting their potential involvement in AD. Hence we evaluated if impairing the prokineticin system activation might have protective effect against neuronal death induced by Aβ. We found that a PKR antagonist concentration-dependently protects CNs against Aβ(1-42)-induced neurotoxicity, by reducing the Aβ-induced PROK2 neuronal up-regulation. Moreover, the antagonist completely rescued LTP impairment in hippocampal slices from 6 month-old Tg2576 AD mice without affecting basal synaptic transmission and paired pulse-facilitation paradigms. These results indicate that PROK2 plays a role in cerebral amyloidosis and that PROK2 antagonists may represent a new approach for ameliorating the defining pathology of AD.

Can prokineticin prevent obesity and insulin resistance?

PURPOSE OF REVIEW

Because of its increasing prevalence and morbi-mortality, obesity is a major health problem. Obesity etiology includes a combination of excess dietary calories and decreased physical activity, coupled with either predisposing genetic factors or metabolic disorders such as insulin resistance. Adipose tissue secretes several metabolically important proteins known as 'adipokines' that play a major role in obesity and insulin resistance. High levels of a newly identified group of adipokines, called prokineticins, have been found in obese adipose tissues. Prokineticins are peptide hormones released principally from macrophages and reproductive organs. They act on the G protein-coupled receptors PKR1 and PKR2. This review aims to provide an overview of current knowledge of the role of prokineticins and their receptors in the development of obesity and insulin resistance.

RECENT FINDINGS

The principal biological effect of prokineticins in the central nervous system is the control of food intake. Nevertheless, peripheral biological effects of prokineticin are associated with increasing insulin sensitivity and suppressing the adipose tissue expansion.

SUMMARY

We outline the biological significance of the central and peripheral effects of prokineticins, and the potential of their receptors as targets for the treatment of obesity and insulin resistance.

A new convenient synthetic method and preliminary pharmacological characterization of triazinediones as prokineticin receptor antagonists

A new efficient synthetic method to obtain prokineticin receptor antagonists based on the triazinedione scaffold is described. In this procedure the overall yield improves from 13% to about 54%, essentially for two factors: 1) N-(chlorocarbonyl) isocyanate is no more used, it represents the yield limiting step with an average yield not exceeding 30%. 2) The Mitsunobu reaction is not involved in the new synthetic scheme avoiding the use of time and solvent consuming column chromatography. All synthesized triazinediones were preliminary pharmacologically screened in vivo for their ability to reduce the Bv8-induced thermal hyperalgesia. In this assay all compounds displayed EC50 values in the picomolar-subpicomolar range, some triazinediones containing a 4-halogen substituted benzyl group in position 5 showed the best activity. The analogues containing a 4-fluorine atom (PC-7) and a 4-bromobenzyl group (PC-25) resulted 10 times more potent than the reference PC-1 that bears a 4-ethylbenzyl group. While the 4-trifluoromethylbenzyl substituted analog (PC-27) was 100 times more potent as compared to PC1.

Role of Prokineticin Receptor-1 in Epicardial Progenitor Cells

G protein-coupled receptors (GPCRs) form a large class of seven transmembrane (TM) domain receptors. The use of endogenous GPCR ligands to activate the stem cell maintenance or to direct cell differentiation would overcome many of the problems currently encountered in the use of stem cells, such as rapid in vitro differentiation and expansion or rejection in clinical applications. This review focuses on the definition of a new GPCR signaling pathway activated by peptide hormones, called “prokineticins”, in epicardium-derived cells (EPDCs). Signaling via prokineticin-2 and its receptor, PKR1, is required for cardiomyocyte survival during hypoxic stress. The binding of prokineticin-2 to PKR1 induces proliferation, migration and angiogenesis in endothelial cells. The expression of prokineticin and PKR1 increases during cardiac remodeling after myocardial infarction. Gain of function of PKR1 in the adult mouse heart revealed that cardiomyocyte-PKR1 signaling activates EPDCs in a paracrine fashion, thereby promoting de novo vasculogenesis. Transient PKR1 gene therapy after myocardial infarction in mice decreases mortality and improves heart function by promoting neovascularization, protecting cardiomyocytes and mobilizing WT1+ cells. Furthermore, PKR1 signaling promotes adult EPDC proliferation and differentiation to adopt endothelial and smooth muscle cell fate, for the induction of de novo vasculogenesis. PKR1 is expressed in the proepicardium and epicardial cells derived from mice kidneys. Loss of PKR1 causes deficits in EPDCs in the neonatal mice hearts and kidneys and impairs vascularization and heart and kidney function. Taken together, these data indicate a novel role for PKR1 in heart-kidney complex via EPDCs.

PROK2/PROKR2 Signaling and Kallmann Syndrome

Kallmann syndrome (KS) is a developmental disease that associates hypogonadism and a deficiency of the sense of smell. The reproductive phenotype of KS results from the primary interruption of the olfactory, vomeronasal, and terminal nerve fibers in the frontonasal region, which in turn disrupts the embryonic migration of neuroendocrine gonadotropin-releasing hormone (GnRH) synthesizing cells from the nose to the brain. This is a highly heterogeneous genetic disease, and mutations in any of the nine genes identified so far have been found in approximately 30% of the KS patients. PROKR2 and PROK2, which encode the G protein-coupled prokineticin receptor-2 and its ligand prokineticin-2, respectively, are two of these genes. Homozygous knockout mice for the orthologous genes exhibit a phenotype reminiscent of the KS features, but biallelic mutations in PROKR2 or PROK2 (autosomal recessive mode of disease transmission) have been found only in a minority of the patients, whereas most patients carrying mutations in these genes are heterozygotes. The mutations, mainly missense mutations, have deleterious effects on PROKR2 signaling in transfected cells, ranging from defective cell surface-targeting of the receptor to defective coupling to G proteins or impaired receptor-ligand interaction, but the same mutations have also been found in apparently unaffected individuals, which suggests a digenic/oligogenic mode of inheritance of the disease in heterozygous patients. This non-Mendelian mode of inheritance has so far been confirmed only in a few patients. However, it may account for the unusually high proportion of KS sporadic cases compared to familial cases.

Pharmacological activity of a Bv8 analogue modified in position 24

BACKGROUND AND PURPOSE

The amphibian peptide Bv8 induces potent nociceptive sensitization in rodents. Its mammalian homologue, prokineticin 2 (PROK2), is strongly up-regulated in inflamed tissues and is a major determinant in triggering inflammatory pain. Bv8 and PROK2 activate two closely related GPCRs, PK(1) and PK(2) , in a relatively non-selective fashion. To characterize better the roles of the two receptors in hyperalgesia and to obtain ligands whose binding affinity and efficacy differed for the two receptors, we modified the Bv8 molecule in regions essential for receptor recognition and activation.

EXPERIMENTAL APPROACH

We modified the Bv8 molecule by substituting Trp in position 24 with Ala (A-24) and compared it with Bv8 for binding and activating PK(1) and PK(2) receptors in cell preparations and in affecting nociceptive thresholds in rodents.

KEY RESULTS

A-24 preferentially bound to PK(2) receptors and activated them with a lower potency (5-fold) than Bv8. When systemically injected, A-24 induced Bv8-like hyperalgesia in rats and in mice, at doses 100 times higher than Bv8. Locally and systemically injected at inactive doses, A-24 antagonized Bv8-induced hyperalgesia. In rat and mouse models of inflammatory and post-surgical pain, A-24 showed potent and long-lasting anti-hyperalgesic activity. Unlike Bv8, A-24 increased β-endorphin levels in mouse brain.

CONCLUSIONS AND IMPLICATIONS

A-24 induced its anti-hyperalgesic effect in rodents by directly blocking nociceptor PK(1) receptors and by activating the central opioid system and the descending pain control pathway through brain PK(2) receptors.

Non-enzymatic proteins from snake venoms: a gold mine of pharmacological tools and drug leads

Non-enzymatic proteins from snake venoms play important roles in the immobilization of prey, and include some large and well-recognized families of toxins. The study of such proteins has expanded not only our understanding of venom toxicity, but also the knowledge of normal and disease states in human physiology. In many cases their characterization has led to the development of powerful research tools, diagnostic techniques, and pharmaceutical drugs. They have further yielded basic understanding of protein structure-function relationships. Therefore a number of studies on these non-enzymatic proteins had major impact on several life science and medical fields. They have led to life-saving therapeutics, the Nobel prize, and development of molecular scalpels for elucidation of ion channel function, vasoconstriction, complement system activity, platelet aggregation, blood coagulation, signal transduction, and blood pressure regulation. Here, we identify research papers that have had significant impact on the life sciences. We discuss how these findings have changed the course of science, and have also included the personal recollections of the original authors of these studies. We expect that this review will provide impetus for even further exciting research on novel toxins yet to be discovered.

EG-VEGF: a key endocrine factor in placental development

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF), also named prokineticin 1, is the canonical member of the prokineticin family. Numerous reports suggest a direct involvement of this peptide in normal and pathological reproductive processes. Recent advances propose EG-VEGF as a key endocrine factor that controls many aspects of placental development and suggest its involvement in the development of preeclampsia (PE), the most threatening pathology of human pregnancy. This review describes the finely tuned action and regulation of EG-VEGF throughout human pregnancy, argues for its clinical relevance as a potential diagnostic marker of the onset of PE, and discusses future research directions for therapeutic targeting of EG-VEGF.

Prokineticin 2 is an endangering mediator of cerebral ischemic injury

Stroke causes brain dysfunction and neuron death, and the lack of effective therapies heightens the need for new therapeutic targets. Here we identify prokineticin 2 (PK2) as a mediator for cerebral ischemic injury. PK2 is a bioactive peptide initially discovered as a regulator of gastrointestinal motility. Multiple biological roles for PK2 have been discovered, including circadian rhythms, angiogenesis, and neurogenesis. However, the role of PK2 in neuropathology is unknown. Using primary cortical cultures, we found that PK2 mRNA is up-regulated by several pathological stressors, including hypoxia, reactive oxygen species, and excitotoxic glutamate. Glutamate-induced PK2 expression is dependent on NMDA receptor activation and extracellular calcium. Enriched neuronal culture studies revealed that neurons are the principal source of glutamate-induced PK2. Using in vivo models of stroke, we found that PK2 mRNA is induced in the ischemic cortex and striatum. Central delivery of PK2 worsens infarct volume, whereas PK2 receptor antagonist decreases infarct volume and central inflammation while improving functional outcome. Direct central inhibition of PK2 using RNAi also reduces infarct volume. These findings indicate that PK2 can be activated by pathological stimuli such as hypoxia-ischemia and excitotoxic glutamate and identify PK2 as a deleterious mediator for cerebral ischemia.

Molecular Cloning and Sequence Analysis of the cDNAs Encoding Toxin-Like Peptides from the Venom Glands of Tarantula Grammostola rosea

Tarantula venom glands produce a large variety of bioactive peptides. Here we present the identification of venom components obtained by sequencing clones isolated from a cDNA library prepared from the venom glands of the Chilean common tarantula, Grammostola rosea. The cDNA sequences of about 1500 clones out of 4000 clones were analyzed after selection using several criteria. Forty-eight novel toxin-like peptides (GTx1 to GTx7, and GTx-TCTP and GTx-CRISP) were predicted from the nucleotide sequences. Among these peptides, twenty-four toxins are ICK motif peptides, eleven peptides are MIT1-like peptides, and seven are ESTX-like peptides. Peptides similar to JZTX-64, aptotoxin, CRISP, or TCTP are also obtained. GTx3 series possess a cysteine framework that is conserved among vertebrate MIT1, Bv8, prokineticins, and invertebrate astakines. GTx-CRISP is the first CRISP-like protein identified from the arthropod venom. Real-time PCR revealed that the transcripts for TCTP-like peptide are expressed in both the pereopodal muscle and the venom gland. Furthermore, a unique peptide GTx7-1, whose signal and prepro sequences are essentially identical to those of HaTx1, was obtained.

Modeling of human prokineticin receptors: interactions with novel small-molecule binders and potential off-target drugs

BACKGROUND AND MOTIVATION

The Prokineticin receptor (PKR) 1 and 2 subtypes are novel members of family A GPCRs, which exhibit an unusually high degree of sequence similarity. Prokineticins (PKs), their cognate ligands, are small secreted proteins of ∼80 amino acids; however, non-peptidic low-molecular weight antagonists have also been identified. PKs and their receptors play important roles under various physiological conditions such as maintaining circadian rhythm and pain perception, as well as regulating angiogenesis and modulating immunity. Identifying binding sites for known antagonists and for additional potential binders will facilitate studying and regulating these novel receptors. Blocking PKRs may serve as a therapeutic tool for various diseases, including acute pain, inflammation and cancer.

METHODS AND RESULTS

Ligand-based pharmacophore models were derived from known antagonists, and virtual screening performed on the DrugBank dataset identified potential human PKR (hPKR) ligands with novel scaffolds. Interestingly, these included several HIV protease inhibitors for which endothelial cell dysfunction is a documented side effect. Our results suggest that the side effects might be due to inhibition of the PKR signaling pathway. Docking of known binders to a 3D homology model of hPKR1 is in agreement with the well-established canonical TM-bundle binding site of family A GPCRs. Furthermore, the docking results highlight residues that may form specific contacts with the ligands. These contacts provide structural explanation for the importance of several chemical features that were obtained from the structure-activity analysis of known binders. With the exception of a single loop residue that might be perused in the future for obtaining subtype-specific regulation, the results suggest an identical TM-bundle binding site for hPKR1 and hPKR2. In addition, analysis of the intracellular regions highlights variable regions that may provide subtype specificity.

Targeting the Wnt pathway in cancer: the emerging role of Dickkopf-3

Aberrant activation of the Wnt signaling pathway is a major trait of many human cancers. Due to its vast implications in tumorigenesis and progression, the Wnt pathway has attracted considerable attention at several molecular levels, also with respect to developing novel cancer therapeutics. Indeed, research in Wnt biology has recently provided numerous clues, and evidence is accumulating that the secreted Wnt antagonist Dickkopf-related protein 3 (Dkk-3) and its regulators may constitute interesting therapeutic targets in the most important human cancers. Based on the currently available literature, we here review the knowledge on the biological role of Dkk-3 as an antagonist of the Wnt signaling pathway, the involvement of Dkk-3 in several stages of tumor development, the genetic and epigenetic mechanisms disrupting DKK3 gene function in cancerous cells, and the potential clinical value of Dkk-3 expression/DKK3 promoter methylation as a biomarker and molecular target in cancer diseases. In conclusion, Dkk-3 rapidly emerges as a key player in human cancer with auspicious tumor suppressive capacities, most of all affecting apoptosis and proliferation. Its gene expression is frequently downregulated by promoter methylation in almost any solid and hematological tumor entity. Clinically, evidence is accumulating of Dkk-3 being both a potential tumor biomarker and effective anti-cancer agent. Although further research is needed, re-establishing Dkk-3 expression in cancer cells holds promise as novel targeted molecular tumor therapy.

Evidence that prokineticin receptor 2 exists as a dimer in vivo

Prokineticins are proteins that regulate diverse biological processes including gastrointestinal motility, angiogenesis, circadian rhythm, and innate immune response. Prokineticins bind two closed related G-protein coupled receptors (GPCRs), PKR1 and PKR2. In general, these receptors act as molecular switches to relay activation to heterotrimeric G-proteins and a growing body of evidence points to the fact that GPCRs exist as homo- or heterodimers. We show here by Western-blot analysis that PKR2 has a dimeric structure in neutrophils. By heterologous expression of PKR2 in Saccharomyces cerevisiae, we examined the mechanisms of intermolecular interaction of PKR2 dimerization. The potential involvement of three types of mechanisms was investigated: coiled-coil, disulfide bridges, and hydrophobic interactions between transmembrane domains. Characterization of differently deleted or site-directed PKR2 mutants suggests that dimerization proceeds through interactions between transmembrane domains. We demonstrate that co-expressing binding-deficient and signaling-deficient forms of PKR2 can re-establish receptor functionality, possibly through a domain-swapping mechanism.

Muscarinic toxins

Muscarinic toxins isolated from the venom of Dendroaspis snakes may interact with a high affinity, large selectivity and various functional properties with muscarinic receptors. Therefore, these toxins are invaluable tools for studying the physiological role, molecular functioning and structural organization of the five subtypes of these G-Protein Coupled Receptors. We review the data on the most relevant results dealing with the isolation/identification, mode of action, structure/function and exploitation of these toxins and finally highlight the unresolved issues related to their pharmacological studies.

Expression of PROKR1 and PROKR2 in human enteric neural precursor cells and identification of sequence variants suggest a role in HSCR

Background

The enteric nervous system (ENS) is entirely derived from neural crest and its normal development is regulated by specific molecular pathways. Failure in complete ENS formation results in aganglionic gut conditions such as Hirschsprung's disease (HSCR). Recently, PROKR1 expression has been demonstrated in mouse enteric neural crest derived cells and Prok-1 was shown to work coordinately with GDNF in the development of the ENS.

Principal Findings

In the present report, ENS progenitors were isolated and characterized from the ganglionic gut from children diagnosed with and without HSCR, and the expression of prokineticin receptors was examined. Immunocytochemical analysis of neurosphere-forming cells demonstrated that both PROKR1 and PROKR2 were present in human enteric neural crest cells. In addition, we also performed a mutational analysis of PROKR1, PROKR2, PROK1 and PROK2 genes in a cohort of HSCR patients, evaluating them for the first time as susceptibility genes for the disease. Several missense variants were detected, most of them affecting highly conserved amino acid residues of the protein and located in functional domains of both receptors, which suggests a possible deleterious effect in their biological function.

Conclusions

Our results suggest that not only PROKR1, but also PROKR2 might mediate a complementary signalling to the RET/GFRα1/GDNF pathway supporting proliferation/survival and differentiation of precursor cells during ENS development. These findings, together with the detection of sequence variants in PROKR1, PROK1 and PROKR2 genes associated to HSCR and, in some cases in combination with RET or GDNF mutations, provide the first evidence to consider them as susceptibility genes for HSCR.

Crustacean hematopoiesis and the astakine cytokines

Major contributions to research in hematopoiesis in invertebrate animals have come from studies in the fruit fly, Drosophila melanogaster, and the freshwater crayfish, Pacifastacus leniusculus. These animals lack oxygen-carrying erythrocytes and blood cells of the lymphoid lineage, which participate in adaptive immune defense, thus making them suitable model animals to study the regulation of blood cells of the innate immune system. This review presents an overview of crustacean blood cell formation, the role of these cells in innate immunity, and how their synthesis is regulated by the astakine cytokines. Astakines are among the first invertebrate cytokines shown to be involved in hematopoiesis, and they can stimulate the proliferation, differentiation, and survival of hematopoietic tissue cells. The astakines and their vertebrate homologues, prokineticins, share similar functions in hematopoiesis; thus, studies of astakine-induced hematopoiesis in crustaceans may not only advance our understanding of the regulation of invertebrate hematopoiesis but may also provide new evolutionary perspectives about this process.