The evolutionary analysis reveals domain fusion of proteins with Frizzled-like CRD domain

Overexpression of Corin Ameliorates Kidney Fibrosis through Inhibition of Wnt/β-Catenin Signaling in Mice

The Wnt/β-catenin pathway represents a promising therapeutic target for mitigating kidney fibrosis. Corin possesses the homologous ligand binding site [Frizzled-cysteine-rich domain (Fz-CRD)] similar to Frizzled proteins, which act as receptors for Wnt. The Fz-CRD has been found in eight different proteins, all of which, except for corin, are known to bind Wnt and regulate its signal transmission. We hypothesized that corin may inhibit the Wnt/β-catenin signaling pathway and thereby reduce fibrogenesis. Reduced expression of corin along with the increased activity of Wnt/β-catenin signaling was found in unilateral ureteral obstruction (UUO) and ureteral ischemia/reperfusion injury (UIRI) models. In vitro, corin bound to the Wnt1 through its Fz-CRDs and inhibit the Wnt1 function responsible for activating β-catenin. Transforming growth factor-β1 inhibited corin expression, accompanied by activation of β-catenin; conversely, overexpression of corin attenuated the fibrotic effects of transforming growth factor-β1. In vivo, adenovirus-mediated overexpression of corin attenuated the progression of fibrosis, which was potentially associated with the inhibition of Wnt/β-catenin signaling and the down-regulation of its target genes after UUO and UIRI. These results suggest that corin acts as an antagonist that protects the kidney from pathogenic Wnt/β-catenin signaling and from fibrosis following UUO and UIRI.

Role of smoothened and sfrp genes in Eupentacta fraudatrix regeneration

The secreted frizzled-related proteins (sfrp) and smoothened (smo) genes and their possible role in the regeneration of internal organs in the holothurian Eupentacta fraudatrix were studied. In this species, two sfrp genes were identified: sfrp1/2/5, sfrp3/4 and one smo gene. Their expression was analysed during regeneration of the aquapharyngeal bulb (AB) and intestine, and these genes were knock down by RNA interference. It has been shown that the expression of these genes is extremely important for the formation of AB. In all animals subjected to knockdown, at 7 days after evisceration, a full-sized AB rudiment was not formed. As a result of sfrp1/2/5 knockdown, the process of extracellular matrix remodelling in AB is interrupted, that leading to clusters of dense connective tissue formation, which slows down cell migration. When sfrp3/4 is knockdown, the connective tissue of AB anlage is completely disrupted and its symmetry is broken. The effect of smo knockdown was expressed in a significant impairment of AB regeneration, when connections between ambulacras were not formed after evisceration. However, despite severe disturbances in AB regeneration, a normal-sized gut anlage developed in all cases, which suggests that the regeneration of the digestive tube and AB occur independently of each other.

Identification of orphan ligand-receptor relationships using a cell-based CRISPRa enrichment screening platform

Secreted proteins, which include cytokines, hormones, and growth factors, are extracellular ligands that control key signaling pathways mediating cell-cell communication within and between tissues and organs. Many drugs target secreted ligands and their cell surface receptors. Still, there are hundreds of secreted human proteins that either have no identified receptors ('orphans') or are likely to act through cell surface receptors that have not yet been characterized. Discovery of secreted ligand-receptor interactions by high-throughput screening has been problematic, because the most commonly used high-throughput methods for protein-protein interaction (PPI) screening are not optimized for extracellular interactions. Cell-based screening is a promising technology for the deorphanization of ligand-receptor interactions, because multimerized ligands can enrich for cells expressing low affinity cell surface receptors, and such methods do not require purification of receptor extracellular domains. Here, we present a proteo-genomic cell-based CRISPR activation (CRISPRa) enrichment screening platform employing customized pooled cell surface receptor sgRNA libraries in combination with a magnetic bead selection-based enrichment workflow for rapid, parallel ligand-receptor deorphanization. We curated 80 potentially high-value orphan secreted proteins and ultimately screened 20 secreted ligands against two cell sgRNA libraries with targeted expression of all single-pass (TM1) or multi-pass transmembrane (TM2+) receptors by CRISPRa. We identified previously unknown interactions in 12 of these screens, and validated several of them using surface plasmon resonance and/or cell binding assays. The newly deorphanized ligands include three receptor protein tyrosine phosphatase (RPTP) ligands and a chemokine-like protein that binds to killer immunoglobulin-like receptors (KIRs). These new interactions provide a resource for future investigations of interactions between the human-secreted and membrane proteomes.

Role of Wnt signaling in synaptic plasticity and memory

Ever since their discoveries, the Wnt pathways have been consistently associated with key features of cellular development, including metabolism, structure and cell fate. The three known pathways (the canonical Wnt/β-catenin and the two non-canonical Wnt/Ca⁺⁺ and Wnt/JNK/PCP pathways) participate in complex networks of interaction with a wide range of regulators of cell function, such as GSK-3β, AKT, PKC and mTOR, among others. These proteins are known to be involved in the formation and maintenance of memory. Currently, studies with Wnt and memory have shown that the canonical and non-canonical pathways play key roles in different processes associated with memory. So, in this review we briefly summarize the different roles that Wnt signaling can play in neurons and in memory, as well as in Alzheimer's disease, focusing towards animal studies. We start with the molecular characterization of the family and its receptors, as well as the most commonly used drugs for pharmacological manipulations. Next, we describe its role in synaptic plasticity and memory, and how the regulations of these pathways affect crucial features of neuronal function. Furthermore, we succinctly present the current knowledge on how the Wnt pathways are implicated in Alzheimer's disease, and how studies are seeing them as a potential candidate for effective treatments. Lastly, we point toward challenges of Wnt research, and how knowledge on these pathways can lead towards a better understanding of neurobiological and pathological processes.

Disorders of FZ-CRD; insights towards FZ-CRD folding and therapeutic landscape

The ER is hub for protein folding. Proteins that harbor a Frizzled cysteine-rich domain (FZ-CRD) possess 10 conserved cysteine motifs held by a unique disulfide bridge pattern which attains a correct fold in the ER. Little is known about implications of disease-causing missense mutations within FZ-CRD families. Mutations in FZ-CRD of Frizzled class receptor 4 (FZD4) and Muscle, skeletal, receptor tyrosine kinase (MuSK) and Receptor tyrosine kinase-like orphan receptor 2 (ROR2) cause Familial Exudative Vitreoretinopathy (FEVR), Congenital Myasthenic Syndrome (CMS), and Robinow Syndrome (RS) respectively. We highlight reported pathogenic inherited missense mutations in FZ-CRD of FZD4, MuSK and ROR2 which misfold, and traffic abnormally in the ER, with ER-associated degradation (ERAD) as a common pathogenic mechanism for disease. Our review shows that all studied FZ-CRD mutants of RS, FEVR and CMS result in misfolded proteins and/or partially misfolded proteins with an ERAD fate, thus we coin them as “disorders of FZ-CRD”. Abnormal trafficking was demonstrated in 17 of 29 mutants studied; 16 mutants were within and/or surrounding the FZ-CRD with two mutants distant from FZ-CRD. These ER-retained mutants were improperly N-glycosylated confirming ER-localization. FZD4 and MuSK mutants were tagged with polyubiquitin chains confirming targeting for proteasomal degradation. Investigating the cellular and molecular mechanisms of these mutations is important since misfolded protein and ER-targeted therapies are in development. The P344R-MuSK kinase mutant showed around 50% of its in-vitro autophosphorylation activity and P344R-MuSK increased two-fold on proteasome inhibition. M105T-FZD4, C204Y-FZD4, and P344R-MuSK mutants are thermosensitive and therefore, might benefit from extending the investigation to a larger number of chemical chaperones and/or proteasome inhibitors. Nonetheless, FZ-CRD ER-lipidation it less characterized in the literature and recent structural data sheds light on the importance of lipidation in protein glycosylation, proper folding, and ER trafficking. Current treatment strategies in-place for the conformational disease landscape is highlighted. From this review, we envision that disorders of FZ-CRD might be receptive to therapies that target FZ-CRD misfolding, regulation of fatty acids, and/or ER therapies; thus paving the way for a newly explored paradigm to treat different diseases with common defects.

Structure, function and disease relevance of Wnt inhibitory factor 1, a secreted protein controlling the Wnt and hedgehog pathways

Wnts and Hedgehogs (Hh) are large, lipid-modified extracellular morphogens that play key roles in embryonic development and stem cell proliferation of Metazoa. Both morphogens signal through heptahelical Frizzled-type receptors of the G-Protein Coupled Receptor family and there are several other similarities that suggest a common evolutionary origin of the Hh and Wnt pathways. There is evidence that the secreted protein, Wnt inhibitory factor 1 (WIF1) modulates the activity of both Wnts and Hhs and may thus contribute to the intertwining of these pathways. In this article, we review the structure, evolution, molecular interactions and functions of WIF1 with major emphasis on its role in carcinogenesis.

Secreted frizzled related protein is a target of PaxB and plays a role in aquiferous system development in the freshwater sponge, Ephydatia muelleri

Canonical and non-canonical Wnt signaling, as well as the Pax/Six gene network, are involved in patterning the freshwater sponge aquiferous system. Using computational approaches to identify transcription factor binding motifs in a freshwater sponge genome, we located putative PaxB binding sites near a Secreted Frizzled Related Protein (SFRP) gene in Ephydatia muelleri. EmSFRP is expressed throughout development, but with highest levels in juvenile sponges. In situ hybridization and antibody staining show EmSFRP expression throughout the pinacoderm and choanoderm in a subpopulation of amoeboid cells that may be differentiating archeocytes. Knockdown of EmSFRP leads to ectopic oscula formation during development, suggesting that EmSFRP acts as an antagonist of Wnt signaling in E. muelleri. Our findings support a hypothesis that regulation of the Wnt pathway by the Pax/Six network as well as the role of Wnt signaling in body plan morphogenesis was established before sponges diverged from the rest of the metazoans.

SFRP5 inhibits the migration and invasion of melanoma cells through Wnt signaling pathway

Background

Secreted frizzled-related protein 5 (SFRP5) plays a key role in the development and progression of multiple tumors. However, the role and underlying mechanisms of SFRP5 in melanoma cells remain unknown.

Materials and methods

We used immunohistochemistry and Western blot analysis to detect the expression of SFRP5 in melanoma tissues and melanoma cells, respectively. Furthermore, both in vitro and in vivo assays were used to determine the effect of SFRP5 on malignant behavior in melanoma cells.

Results

We found that SFRP5 was markedly downregulated in melanoma tissues and cell lines. The SFRP5 overexpression exhibited no effect on the proliferation and apoptosis of melanoma cells but markedly suppressed the migration and invasion of melanoma cells in vitro. Regarding mechanisms, the SFRP5 overexpression inhibited the migration and invasion of melanoma cells by suppressing the epithelial–mesenchymal transition process and decreasing the matrix metalloproteinase-2/9 expression through the Wnt signaling pathway. Finally, in a xenograft animal model, we illustrated that the SFRP5 overexpression suppressed the tumor growth by decreasing angiogenesis and declined lung metastasis.

Conclusion

This study suggests that SFRP5 expression could be potentially useful in the invasion and metastasis of melanoma and serve as a putative promising target for human melanoma therapy.

Canonical and non-canonical Wnt signaling pathways define the expression domains of Frizzled 5/8 and Frizzled 1/2/7 along the early anterior-posterior axis in sea urchin embryos

The spatiotemporal expression of Frizzled receptors is critical for patterning along the early anterior-posterior axis during embryonic development in many animal species. However, the molecular mechanisms that regulate the expression of Frizzled receptors are incompletely understood in any species. In this study, I examine how the expression of two Frizzled receptors, Fzl1/2/7 and Fzl5/8, is controlled by the Wnt signaling network which directs specification and positioning of early regulatory states along the anterior-posterior (AP) axis of sea urchin embryos. I used a combination of morpholino- and dominant negative-mediated interference to knock down each Wnt signaling pathway involved in the AP Wnt signaling network. I found that the expression of zygotic fzl5/8 as well as that of the anterior neuroectoderm gene regulatory network (ANE GRN) is activated by an unknown broadly expressed regulatory state and that posterior Wnt/β-catenin signaling is necessary to down regulate fzl5/8's expression in posterior blastomeres. I show that zygotic expression of fzl1/2/7 in the equatorial ectodermal belt is dependent on an uncharacterized regulatory mechanism that works in the same cells receiving the TGF-β signals patterning this territory along the dorsal-ventral axis. In addition, my data indicate that Fzl1/2/7 signaling represses its own expression in a negative feedback mechanism. Finally, we discovered that a balance between the activities of posterior Wnt8 and anterior Dkk1 is necessary to establish the correct spatial expression of zygotic fzl12/7 expression in the equatorial ectodermal domain during blastula and gastrula stages. Together, these studies lead to a better understanding of the complex interactions among the three Wnt signaling pathway governing AP axis specification and patterning in sea urchin embryos.

Matricellular proteins in cancer: a focus on secreted Frizzled-related proteins

Tumours are complex entities, wherein cancer cells interact with myriad soluble, insoluble and cell associated factors. These microenvironmental mediators regulate tumour growth, progression and metastasis, and are produced by cancer cells and by stromal components such as fibroblast, adipocytes and immune cells. Through their ability to bind to extracellular matrix proteins, cell surface receptors and growth factors, matricellular proteins enable a dynamic reciprocity between cancer cells and their microenvironment. Hence, matricellular proteins play a critical role in tumour progression by regulating where and when cancer cells are exposed to key growth factors and regulatory proteins. Recent studies suggest that, in addition to altering Wingless (Wnt) signalling, certain members of the Secreted Frizzled Related Protein (sFRP) family are matricellular in nature. In this review, we outline the importance of matricellular proteins in cancer, and discuss how sFRPs may function to both inhibit and promote cancer progression in a context-dependent manner. By considering the matricellular functionality of sFRPs, we may better understand their apparently paradoxical roles in cancers.

Association of rs2271037 and rs3749585 polymorphisms in CORIN with susceptibility to hypertension in a Chinese Han population: A case-control study

Corins are membrane-bound protease that regulates blood pressure by activating the natriuretic peptides. These pro-atrial natriuretic peptide convertases are essential for sodium homeostasis and normal blood pressure. CORIN variants have been identified in humans and other animals, but no studies of CORIN polymorphisms have been conducted in northeastern China. This study aims to investigate the association of 2 single nucleotide polymorphisms (SNPs) in CORIN (rs2271037 and rs3749585) with hypertension, as well as their potential interactions with some risk factors of hypertension in a Han population of northeastern China. A case-control study, including 402 patients with hypertension and 406 participants with normal blood pressure, was conducted in Liaoning province. SNP genotyping was carried out by high resolution melting (HRM) after polymerase chain reaction amplifications. Since rs3749585 is located in 3' untranslated region (UTR) of CORIN, in silico analysis was used to predict target micro RNAs on TargetScan, miRanda, and DIANA-microT. As a result, mutant T allele in rs2271037 (odds ratio [OR], 1.693; 95% confidence [CI], 1.528-1.877; p < 0.001) and C allele in rs3749585 (OR, 1.114; 95% CI 1.011-1.227; p = 0.029) increased the risk of hypertension, comparing with wild G allele and T allele, respectively. Patients with genotype TT (OR, 10.209; 95% CI, 6.414-16.250; p < 0.001) and GT (OR, 1.730; 95% CI, 1.226-2.443; p = 0.002) have higher risk of hypertension than those with genotype GG. SNP rs2271037 was significantly associated with susceptibility to hypertension in all genetic models (dominant model: OR, 2.879; 95% CI, 2.080-3.986; p < 0.001; recessive model: OR, 7.159; 95% CI, 4.779-10.724; p < 0.001; additive model: OR, 1.535; 95% CI, 1.163-2.027; p = 0.002). SNP rs3749585 was significantly correlated with hypertension susceptibility only in dominant model (OR, 1.533; 95% CI, 1.073-2.189; p = 0.019), but not in recessive model (OR, 1.220; 95% CI, 0.906-1.644; p = 0.191) or additive model (OR, 0.915; 95% CI, 0.694-1.205; p = 0.527). After adjusting for age, gender, body mass index (BMI), smoking, low-density lipoprotein cholesterol, and serum sodium level in logistic models, the same statistical results were obtained. Interaction study showed the association between CORIN polymorphisms and hypertension could be changed by overweight (BMI ≥ 25 kg/m²). In silico analyses implicated hsa-miR-495 as a target miRNA that potentially interacts with the 3' UTR of CORIN. In conclusion, polymorphisms of rs2271037 and rs3749585 in CORIN were significantly associated with hypertension in a Han population of northeastern China. The mutant-type T allele of rs2271037 and C allele of rs3749585 might increase the susceptibility to hypertension in this population.

A novel gene's role in an ancient mechanism: secreted Frizzled-related protein 1 is a critical component in the anterior-posterior Wnt signaling network that governs the establishment of the anterior neuroectoderm in sea urchin embryos

The anterior neuroectoderm (ANE) in many deuterostome embryos (echinoderms, hemichordates, urochordates, cephalochordates, and vertebrates) is progressively restricted along the anterior-posterior axis to a domain around the anterior pole. In the sea urchin embryo, three integrated Wnt signaling branches (Wnt/β-catenin, Wnt/JNK, and Wnt/PKC) govern this progressive restriction process, which begins around the 32- to 60-cell stage and terminates by the early gastrula stage. We previously have established that several secreted Wnt modulators of the Dickkopf and secreted Frizzled-related protein families (Dkk1, Dkk3, and sFRP-1/5) are expressed within the ANE and play important roles in modulating the Wnt signaling network during this process. In this study, we use morpholino and dominant-negative interference approaches to characterize the function of a novel Frizzled-related protein, secreted Frizzled-related protein 1 (sFRP-1), during ANE restriction. sFRP-1 appears to be related to a secreted Wnt modulator, sFRP3/4, that is essential to block Wnt signaling and establish the ANE in vertebrates. Here, we show that the sea urchin sFRP3/4 orthologue is not expressed during ANE restriction in the sea urchin embryo. Instead, our results indicate that ubiquitously expressed maternal sFRP-1 and Fzl1/2/7 signaling act together as early as the 32- to 60-cell stage to antagonize the ANE restriction mechanism mediated by Wnt/β-catenin and Wnt/JNK signaling. Then, starting from the blastula stage, Fzl5/8 signaling activates zygotic sFRP-1 within the ANE territory, where it works with the secreted Wnt antagonist Dkk1 (also activated by Fzl5/8 signaling) to antagonize Wnt1/Wnt8-Fzl5/8-JNK signaling in a negative feedback mechanism that defines the outer ANE territory boundary. Together, these data indicate that maternal and zygotic sFRP-1 protects the ANE territory by antagonizing the Wnt1/Wnt8-Fzl5/8-JNK signaling pathway throughout ANE restriction, providing precise spatiotemporal control of the mechanism responsible for the establishment of the ANE territory around the anterior pole of the sea urchin embryo.

Complexity of the Wnt/β‑catenin pathway: Searching for an activation model

Wnt signaling refers to a conserved signaling pathway, widely studied due to its roles in cellular communication, cell fate decisions, development and cancer. However, the exact mechanism underlying inhibition of the GSK phosphorylation towards β-catenin and activation of the pathway after biding of Wnt ligand to its cognate receptors at the plasma membrane remains unclear. Wnt target genes are widely spread over several animal phyla. They participate in a plethora of functions during the development of an organism, from axial specification, gastrulation and organogenesis all the way to regeneration and repair in adults. Temporal and spatial oncogenetic re-activation of Wnt signaling almost certainly leads to cancer. Wnt signaling components have been extensively studied as possible targets in anti-cancer therapies. In this review we will discuss one of the most intriguing questions in this field, that is how β-catenin, a major component in this pathway, escapes the destruction complex, gets stabilized in the cytosol and it is translocated to the nucleus where it acts as a co-transcription factor. Four major models have evolved during the past 20years. We dissected each of them along with current views and future perspectives on this pathway. This review will focus on the molecular mechanisms by which Wnt proteins modulate β-catenin cytoplasmic levels and the relevance of this pathway for the development and cancer.

Role of corin in the regulation of blood pressure

PURPOSE OF REVIEW

Corin is a transmembrane protease that activates atrial natriuretic peptide (ANP), an important hormone in regulating salt-water balance and blood pressure. This review focuses on the regulation of corin function and potential roles of corin defects in hypertensive, heart, and renal diseases.

RECENT FINDINGS

Proprotein convertase subtilisin/kexin-6 has been identified as a primary enzyme that converts zymogen corin to an active protease. Genetic variants that impair corin intracellular trafficking, cell surface expression, and zymogen activation have been found in patients with hypertension, cardiac hypertrophy, and pre-eclampsia. Reduced corin expression has been detected in animal models of cardiomyopathies and in human failing hearts. Low levels of circulating soluble corin have been reported in patients with heart disease and stroke. Corin, ANP and natriuretic peptide receptor-A mRNAs, and proteins have been colocalized in human renal segments, suggesting a corin-ANP autocrine function in the kidney.

SUMMARY

Corin is a key enzyme in the natriuretic peptide system. The latest findings indicate that corin-mediated ANP production may act in a tissue-specific manner to regulate cardiovascular and renal function. Corin defects may contribute to major diseases such as hypertension, heart failure, pre-eclampsia, and kidney disease.

Diverging roles for Lrp4 and Wnt signaling in neuromuscular synapse development during evolution

In this study, Remédio et al. use mice and zebrafish to show that muscle prepatterning in mammals and zebrafish is established by different mechanisms. Their findings demonstrate that Agrin/Lrp4/MuSK signaling plays an essential role in neuromuscular synapse formation in both fish and mammals, whereas Wnt signaling is dispensable.

Motor axons approach muscles that are prepatterned in the prospective synaptic region. In mice, prepatterning of acetylcholine receptors requires Lrp4, a LDLR family member, and MuSK, a receptor tyrosine kinase. Lrp4 can bind and stimulate MuSK, strongly suggesting that association between Lrp4 and MuSK, independent of additional ligands, initiates prepatterning in mice. In zebrafish, Wnts, which bind the Frizzled (Fz)-like domain in MuSK, are required for prepatterning, suggesting that Wnts may contribute to prepatterning and neuromuscular development in mammals. We show that prepatterning in mice requires Lrp4 but not the MuSK Fz-like domain. In contrast, prepatterning in zebrafish requires the MuSK Fz-like domain but not Lrp4. Despite these differences, neuromuscular synapse formation in zebrafish and mice share similar mechanisms, requiring Lrp4, MuSK, and neuronal Agrin but not the MuSK Fz-like domain or Wnt production from muscle. Our findings demonstrate that evolutionary divergent mechanisms establish muscle prepatterning in zebrafish and mice.

Comparative and evolutionary studies of ALDH18A1 genes and proteins

Vertebrate ALDH18A1 genes encode a bifunctional mitochondrial enzyme, catalyzing a 2-step conversion of glutamate to glutamyl semialdehyde, subsequently converted into proline, ornithine and arginine. Bioinformatic analyses of vertebrate and invertebrate genomes were undertaken using known ALDH18A1 amino acid sequences. G5K (glutamyl kinase) and GPR (glutamyl phosphate reductase) domain sequences were identified for all vertebrate and invertebrate genomes examined, whereas bacterial sequences encoded separate enzymes. Vertebrate ALDH18A1 (also called P5CS) sequences were highly conserved throughout vertebrate evolution. A mechanism for generating two major vertebrate ALDH18A1 isoforms is proposed with 'a' isoform containing Asn239-Val240 with wide tissue expression, whereas the 'b' isoform lacking the dipeptide has been reported in gut tissues. Phylogenetic analyses describe the relationships and potential origins of the ALDH18A1 gene during vertebrate and invertebrate evolution and a proposal for generating the bifunctional vertebrate and invertebrate ALDH18A1 gene from a bacterial operon (proBA) encoding G5K and GPR. A more recent Aldh18a1 gene duplication event has apparently occurred with a primordial rat genome.

In silico prediction of the G-protein coupled receptors expressed during the metamorphic molt of Sagmariasus verreauxi (Crustacea: Decapoda) by mining transcriptomic data: RNA-seq to repertoire

Against a backdrop of food insecurity, the farming of decapod crustaceans is a rapidly expanding and globally significant source of food protein. Sagmariasus verreauxi spiny lobster, the subject of this study, are decapods of underdeveloped aquaculture potential. Crustacean neuropeptide G-protein coupled receptors (GPCRs) mediate endocrine pathways that are integral to animal fecundity, growth and survival. The potential use of novel biotechnologies to enhance GPCR-mediated physiology may assist in improving the health and productivity of farmed decapod populations. This study catalogues the GPCRs expressed in the early developmental stages, as well as adult tissues, with a view to illuminating key neuropeptide receptors. De novo assembled contiguous sequences generated from transcriptomic reads of metamorphic and post metamorphic S. verreauxi were filtered for seven transmembrane domains, and used as a reference for iterative re-mapping. Subsequent putative GPCR open reading frames (ORFs) were BLAST annotated, categorised, and compared to published orthologues based on phylogenetic analysis. A total of 85 GPCRs were digitally predicted, that represented each of the four arthropod subfamilies. They generally displayed low-level and non-differential metamorphic expression with few exceptions that we examined using RT-PCR and qPCR. Two putative CHH-like neuropeptide receptors were annotated. Three dimensional structural modelling suggests that these receptors exhibit a conserved extracellular ligand binding pocket, providing support to the notion that these receptors co-evolved with their ligands across Decapoda. This perhaps narrows the search for means to increase productivity of farmed decapod populations.

Structure, phylogeny, and expression of the frizzled-related gene family in the lophotrochozoan annelid Platynereis dumerilii

Background

Wnt signaling pathways are highly conserved signal transduction pathways important for axis formation, cell fate specification, and organogenesis throughout metazoan development. Within the various Wnt pathways, the frizzled transmembrane receptors (Fzs) and secreted frizzled-related proteins (sFRPs) play central roles in receiving and antagonizing Wnt signals, respectively. Despite their importance, very little is known about the frizzled-related gene family (fzs & sfrps) in lophotrochozoans, especially during early stages of spiralian development. Here we ascertain the frizzled-related gene complement in six lophotrochozoan species, and determine their spatial and temporal expression pattern during early embryogenesis and larval stages of the marine annelid Platynereis dumerilii.

Results

Phylogenetic analyses confirm conserved homologs for four frizzled receptors (Fz1/2/7, Fz4, Fz5/8, Fz9/10) and sFRP1/2/5 in five of six lophotrochozoan species. The sfrp3/4 gene is conserved in one, divergent in two, and evidently lost in three lophotrochozoan species. Three novel fz-related genes (fzCRD1-3) are unique to Platynereis. Transcriptional profiling and in situ hybridization identified high maternal expression of fz1/2/7, expression of fz9/10 and fz1/2/7 within animal and dorsal cell lineages after the 32-cell stage, localization of fz5/8, sfrp1/2/5, and fzCRD-1 to animal-pole cell lineages after the 80-cell stage, and no expression for fz4, sfrp3/4, and fzCRD-2, and -3 in early Platynereis embryos. In later larval stages, all frizzled-related genes are expressed in distinct patterns preferentially in the anterior hemisphere and less in the developing trunk.

Conclusions

Lophotrochozoans have retained a generally conserved ancestral bilaterian frizzled-related gene complement (four Fzs and two sFRPs). Maternal expression of fz1/2/7, and animal lineage-specific expression of fz5/8 and sfrp1/2/5 in early embryos of Platynereis suggest evolutionary conserved roles of these genes to perform Wnt pathway functions during early cleavage stages, and the early establishment of a Wnt inhibitory center at the animal pole, respectively. Numerous frizzled receptor-expressing cells and embryonic territories were identified that might indicate competence to receive Wnt signals during annelid development. An anterior bias for frizzled-related gene expression in embryos and larvae might point to a polarity of Wnt patterning systems along the anterior–posterior axis of this annelid.

Electronic supplementary material

The online version of this article (doi:10.1186/s13227-015-0032-4) contains supplementary material, which is available to authorized users.

A novel cytoplasmic tail motif regulates mouse corin expression on the cell surface

Type II transmembrane serine proteases (TTSPs) are important in many biological processes. Cell surface expression is critical for TTSP activation and function. To date, the mechanism underlying TTSP cell surface expression is poorly understood. Corin is a TTSP and acts as the pro-atrial natriuretic peptide convertase that is essential for sodium homeostasis and normal blood pressure. In this study, we investigated how cytoplasmic tail sequences may regulate corin expression and activation on the cell surface. By site-directed mutagenesis, we made mouse corin proteins with truncations or point-mutations in the cytoplasmic tail. We expressed the mutants in transfected HEK293 cells and analyzed corin cell surface expression and activation by Western blotting and flow cytometry. We found that corin truncation mutants lacking a Lys-Phe-Gln sequence at residues 71-73 had higher levels of cell surface expression and activation compared with that in wild-type corin. When Lys-71, Phe-72 and Gln-73 residues were mutated together, but not individually, in corin with the full-length cytoplasmic tail, increased levels of cell surface expression and zymogen activation were also observed. These results indicate that residues Lys-71, Phe-72 and Gln-73 serve as a novel retention motif in the intracellular pathway to regulate corin cell surface expression and activation.