Laeverin/Aminopeptidase Q, a Novel Bestatin-sensitive Leucine Aminopeptidase Belonging to the M1 Family of Aminopeptidases

Vitamin B5 is a context-dependent dietary regulator of nociception

Chronic pain has an enormous impact on the quality of life of billions of patients, families, and caregivers worldwide. Current therapies do not adequately address pain for most patients. A basic understanding of the conserved genetic framework controlling pain may help us develop better, non-addictive pain therapies. Here, we identify new conserved and druggable analgesic targets using the tissue-specific functional genomic screening of candidate "pain" genes in fly. From these efforts, we describe 23 new pain genes for further consideration. This included Acsl, a fatty acid-metabolizing enzyme, and mammalian orthologs involved in arachidonic acid metabolism. The Acsl knockdown and mutant larvae showed delayed nocifensive responses to localized and global noxious heat. Mechanistically, the Acsl knockdown reduced dendritic branching of nociceptive neurons. Surprisingly, the pain phenotype in these animals could be rescued through dietary intervention with vitamin B5, highlighting the interplay between genetics, metabolism, and nutrient environment to establish sensory perception thresholds. Together, our functional genomic screening within the sensory nociceptor has identified new nociception genes that provide a better understanding of pain biology and can help guide the development of new painkillers.

Galectin-13 and Laeverin Levels Interfere with Human Fetoplacental Growth

Galectin-13 (Gal-13) is predominantly produced by the syncytiotrophoblast, while laeverin is expressed on the outgrowing extravillous trophoblast, and both are thought to be biomarkers of preeclampsia. The aim of this study was to assess the correlation between concentrations of Gal-13 and laeverin measured in maternal serum and amniotic fluid at 16-22 weeks of gestation and the sonographic assessment of the fetoplacental measurements. Fetal biometric data and placental volume and perfusion indices were measured in 62 singleton pregnancies. Serum and amniotic levels of Gal-13 and laeverin levels were measured using a sandwich ELISA. Both amniotic fluid and serum Gal-13 levels expressed a negative correlation to the plasma laeverin level in mid-pregnancy. Serum laeverin level correlated positively with the gestational length at delivery (β = 0.39, p < 0.05), while the amniotic laeverin level correlated well with the abdominal circumference of the fetus (β = 0.44, p < 0.05). Furthermore, laeverin level in the amnion correlated positively with the estimated fetal weight (β = 0.48, p < 0.05) and with the placental volume (β = 0.32, p < 0.05). Logistic regression analyses revealed that a higher circulating Gal-13 level represents a slightly significant risk factor (OR: 1.01) for hypertension-related diseases during pregnancy. It is a novelty that laeverin can be detected in the amniotic fluid, and amnion laeverin concentration represents a potential biomarker of fetoplacental growth.

Laeverin/aminopeptidase Q induces indoleamine 2,3-dioxygenase-1 in human monocytes

Human extravillous trophoblast (EVT) invades the maternal endometrium and reconstructs uterine spiral arteries cooperatively with maternal immune cells. Although EVT has allogeneic paternal antigens, the maternal immune system does not reject it. Here, we found that laeverin (LVRN), an EVT-specific cell surface peptidase, interacts with monocytes to produce indoleamine 2,3-dioxygenase-1 (IDO1). LVRN-transfected Swan71 cells, a cytotrophoblast-derived cell line, and increased IDO1 expression in PBMC under cell-to-cell interacting conditions. Soluble recombinant LVRN (r-LVRN) interacted with CD14-positive monocytes and induced their IDO1 expression without the intervention of other immune cell populations. LVRN-induced IDO1 production was promoted in PMA-activated monocyte-like THP-1 cells. Furthermore, r-LVRN decreased the tryptophan level and increased the kynurenine/tryptophan ratio in the culture media of the PMA-treated THP-1 cells. These findings suggest that LVRN is one of the key molecules that mediate the interaction between EVT and monocytes/macrophages and creates an immunosuppressive environment at the maternal-fetal interface in the uterus.

Spheroid formation induces chemokine production in trophoblast-derived Swan71 cells

PROBLEM

In the cell column of anchoring villi, the cytotrophoblast differentiates into extravillous trophoblast (EVT) and invades the endometrium in contact with maternal immune cells. Recently, chemokines were proposed to regulate the decidual immune response. To investigate the roles of chemokines around the anchoring villi, we examined the expression profiles of chemokines in the first-trimester trophoblast-derived Swan71 cells using a three-dimensional culture model.

METHOD OF STUDY

The gene expressions in the spheroid-formed Swan71 cells were examined by microarray and qPCR analyses. The protein expressions were examined by immunochemical staining. The chemoattractant effects of spheroid-formed Swan71 cells were examined by migration assay using monocyte-derived THP-1 cells.

RESULTS

The expressions of an EVT marker, laeverin, and matrix metalloproteases, MMP2 and MMP9, were increased in the spheroid-cultured Swan71 cells. Microarray and qPCR analysis revealed that mRNA expressions of various chemokines, CCL2, CCL7, CCL20, CXCL1, CXCL2, CXCL5, CXCL6, CXCL8, and CXCL10, in the spheroid-cultured Swan71 cells were up-regulated as compared with those in the monolayer-cultured Swan71 cells. These expressions were significantly suppressed by hypoxia. Migration assay showed that culture media derived from the spheroid-formed Swan71 cells promoted THP-1 cell migration.

CONCLUSION

This study indicated that chemokine expressions in Swan71 cells increase under a spheroid-forming culture and the culture media have chemoattractant effects. Since three-dimensional cell assembling in the spheroid resembles the structure of the cell column, this study also suggests that chemokines play important roles in the interaction between EVT and immune cells in their early differentiation stage.

Whole Exome Sequencing to Find Candidate Variants for the Prediction of Kidney Transplantation Efficacy

INTRODUCTION

Kidney transplantation is the optimal treatment strategy for some end-stage renal disease (ESRD); however, graft survival and the success of the transplantation depend on several elements, including the genetics of recipients. In this study, we evaluated exon loci variants based on a high-resolution Next Generation Sequencing (NGS) method.

METHODS

We evaluated whole-exome sequencing (WES) of transplanted kidney recipients in a prospective study. The study involved a total of 10 patients (5 without a history of rejection and 5 with). About five milliliters of blood were collected for DNA extraction, followed by whole-exome sequencing based on molecular inversion probes (MIPs).

RESULTS

Sequencing and variant filtering identified nine pathogenic variants in rejecting patients (low survival). Interestingly, in five patients with successful kidney transplantation, we found 86 SNPs in 63 genes 61 were variants of uncertain significance (VUS), 5 were likely pathogenic, and five were likely benign/benign. The only overlap between rejecting and non-rejecting patients was SNPs rs529922492 in rejecting and rs773542127 in non-rejecting patients' MUC4 gene.

CONCLUSIONS

Nine variants of rs779232502, rs3831942, rs564955632, rs529922492, rs762675930, rs569593251, rs192347509, rs548514380, and rs72648913 have roles in short graft survival.

High frequency of an otherwise rare phenotype in a small and isolated tiger population

Most endangered species exist today in small populations, many of which are isolated. Evolution in such populations is largely governed by genetic drift. Empirical evidence for drift affecting striking phenotypes based on substantial genetic data are rare. Approximately 37% of tigers (Panthera tigris) in the Similipal Tiger Reserve (in eastern India) are pseudomelanistic, characterized by wide, merged stripes. Camera trap data across the tiger range revealed the presence of pseudomelanistic tigers only in Similipal. We investigated the genetic basis for pseudomelanism and examined the role of drift in driving this phenotype's frequency. Whole-genome data and pedigree-based association analyses from captive tigers revealed that pseudomelanism cosegregates with a conserved and functionally important coding alteration in Transmembrane Aminopeptidase Q (Taqpep), a gene responsible for similar traits in other felid species. Noninvasive sampling of tigers revealed a high frequency of the Taqpep p.H454Y mutation in Similipal (12 individuals, allele frequency = 0.58) and absence from all other tiger populations (395 individuals). Population genetic analyses confirmed few (minimal number) tigers in Similipal, and its genetic isolation, with poor geneflow. Pairwise FST (0.33) at the mutation site was high but not an outlier. Similipal tigers had low diversity at 81 single nucleotide polymorphisms (mean heterozygosity = 0.28, SD = 0.27). Simulations were consistent with founding events and drift as possible drivers for the observed stark difference of allele frequency. Our results highlight the role of stochastic processes in the evolution of rare phenotypes. We highlight an unusual evolutionary trajectory in a small and isolated population of an endangered species.

Developmental genetics of color pattern establishment in cats

Intricate color patterns are a defining aspect of morphological diversity in the Felidae. We applied morphological and single-cell gene expression analysis to fetal skin of domestic cats to identify when, where, and how, during fetal development, felid color patterns are established. Early in development, we identify stripe-like alterations in epidermal thickness preceded by a gene expression pre-pattern. The secreted Wnt inhibitor encoded by Dickkopf 4 plays a central role in this process, and is mutated in cats with the Ticked pattern type. Our results bring molecular understanding to how the leopard got its spots, suggest that similar mechanisms underlie periodic color pattern and periodic hair follicle spacing, and identify targets for diverse pattern variation in other mammals.

Mining the 99 Lives Cat Genome Sequencing Consortium database implicates genes and variants for the Ticked locus in domestic cats (Felis catus)

Tabby patterns of fur coats are defining characteristics in wild and domestic felids. Historically, three autosomal alleles at one locus (Tabby): Abyssinian (Ta ; a.k.a. ticked), mackerel (Tm ; a.k.a. striped) and blotched (tb ; a.k.a. classic, blotched) were thought to control these patterns in domestic cats and their breeds. Currently, at least three loci influence cat tabby markings, two of which are designated Tabby and Ticked. The Tabby locus is laeverin (LVRN) and affects the mackerel and blotched patterns. The unidentified gene for the Ticked locus on cat chromosome B1 was suggested to control the presence or absence of the ticked pattern (Tabby - Abyssinian (Ta ; a.k.a. ticked). The cat reference genome (Cinnamon, the Abyssinian) has the ticked phenotype and the variant dataset and coat phenotypes from the 99 Lives Cat Genome Consortium (195 cats) were used to identify candidate genes and variants associated with the Ticked locus. Two strategies were used to find the Ticked allele(s), one considered Cinnamon with the reference allele or heterozygous (Strategy A) and the other considered Cinnamon as having the variant allele or heterozygous (Strategy B). For Strategy A, two variants in Dickkopf Wnt Signaling Pathway Inhibitor 4 (DKK4), a p.Cys63Tyr (B1:41621481, c.188G>A) and a less common p.Ala18Val (B1:42620835, c.53C>T) variant are suggested as two alleles influencing the Ticked phenotype. Bioinformatic and molecular modeling analysis suggests that these changes disrupt a key disulfide bond in the Dkk4 cysteine-rich domain 1 or Dkk4 signal peptide cleavage respectively. All coding variants were excluded as Ticked alleles using Strategy B.

PRG2 and AQPEP are misexpressed in fetal membranes in placenta previa and percreta†

The obstetrical conditions placenta accreta spectrum (PAS) and placenta previa are a significant source of pregnancy-associated morbidity and mortality, yet the specific molecular and cellular underpinnings of these conditions are not known. In this study, we identified misregulated gene expression patterns in tissues from placenta previa and percreta (the most extreme form of PAS) compared with control cases. By comparing this gene set with existing placental single-cell and bulk RNA-Seq datasets, we show that the upregulated genes predominantly mark extravillous trophoblasts. We performed immunofluorescence on several candidate molecules and found that PRG2 and AQPEP protein levels are upregulated in both the fetal membranes and the placental disk in both conditions. While this increased AQPEP expression remains restricted to trophoblasts, PRG2 is mislocalized and is found throughout the fetal membranes. Using a larger patient cohort with a diverse set of gestationally aged-matched controls, we validated PRG2 as a marker for both previa and PAS and AQPEP as a marker for only previa in the fetal membranes. Our findings suggest that the extraembryonic tissues surrounding the conceptus, including both the fetal membranes and the placental disk, harbor a signature of previa and PAS that is characteristic of EVTs and that may reflect increased trophoblast invasiveness.

Overexpression of LVRN impedes the invasion of trophoblasts by inhibiting epithelial-mesenchymal transition

Laeverin (LVRN) was first detected on the outer layer of the chorion laeve and migrating extravillous trophoblasts (EVTs). It is an enzyme that plays an important role in the placentation and pathophysiology of preeclampsia (PE). Previous studies have indicated that LVRN may be required for the invasion of human trophoblast cells. Paradoxically, LVRN was found to be highly expressed in the trophoblasts of PE patients with impaired invasive capacities. In this study, we detected the expression of LVRN in the placentas of PE patients (n=5) and normal term pregnancy women (n=5) as a control group by immunohistochemistry. LVRN was elevated in decidua (P=0.0083) and villi (P=0.0079) of PE patients. Next, LVRN was overexpressed via adeno-associated virus-mediated gene transfer in trophoblastic cell lines HTR8, Swan71, and JAR. Matrigel transwell assay and wound healing assay showed that overexpression of LVRN impeded the invasion of these three cell lines. Western blot analysis showed that LVRN overexpression caused downregulation of N-cadherin and vimentin and upregulation of E-cadherin, suggesting the inhibitory role of LVRN in epithelial-mesenchymal transition (EMT). Moreover, our data indicated that long noncoding RNA NONSTAT103348 (lnc10-7) was elevated in PE patients. Silencing lnc10-7 led to decreased LVRN expression. Taken together, although the basal level of LVRN may be crucial for cell invasion, overexpression of LVRN may abrogate the cell invasiveness, suggesting a multifaceted role of LVRN in the pathogenesis of PE.

Coding transcriptome analyses reveal altered functions underlying immunotolerance of PEG-fused rat sciatic nerve allografts

BACKGROUND

Current methods to repair ablation-type peripheral nerve injuries (PNIs) using peripheral nerve allografts (PNAs) often result in poor functional recovery due to immunological rejection as well as to slow and inaccurate outgrowth of regenerating axonal sprouts. In contrast, ablation-type PNIs repaired by PNAs, using a multistep protocol in which one step employs the membrane fusogen polyethylene glycol (PEG), permanently restore sciatic-mediated behaviors within weeks. Axons and cells within PEG-fused PNAs remain viable, even though outbred host and donor tissues are neither immunosuppressed nor tissue matched. PEG-fused PNAs exhibit significantly reduced T cell and macrophage infiltration, expression of major histocompatibility complex I/II and consistently low apoptosis. In this study, we analyzed the coding transcriptome of PEG-fused PNAs to examine possible mechanisms underlying immunosuppression.

METHODS

Ablation-type sciatic PNIs in adult Sprague-Dawley rats were repaired using PNAs and a PEG-fusion protocol combined with neurorrhaphy. Electrophysiological and behavioral tests confirmed successful PEG-fusion of PNAs. RNA sequencing analyzed differential expression profiles of protein-coding genes between PEG-fused PNAs and negative control PNAs (not treated with PEG) at 14 days PO, along with unoperated control nerves. Sequencing results were validated by quantitative reverse transcription PCR (RT-qPCR), and in some cases, immunohistochemistry.

RESULTS

PEG-fused PNAs display significant downregulation of many gene transcripts associated with innate and adaptive allorejection responses. Schwann cell-associated transcripts are often upregulated, and cellular processes such as extracellular matrix remodeling and cell/tissue development are particularly enriched. Transcripts encoding several potentially immunosuppressive proteins (e.g., thrombospondins 1 and 2) also are upregulated in PEG-fused PNAs.

CONCLUSIONS

This study is the first to characterize the coding transcriptome of PEG-fused PNAs and to identify possible links between alterations of the extracellular matrix and suppression of the allorejection response. The results establish an initial molecular basis to understand mechanisms underlying PEG-mediated immunosuppression.

Promoting Roles of Embryonic Signals in Embryo Implantation and Placentation in Cooperation with Endocrine and Immune Systems

Embryo implantation in the uterus is an essential process for successful pregnancy in mammals. In general, the endocrine system induces sufficient embryo receptivity in the endometrium, where adhesion-promoting molecules increase and adhesion-inhibitory molecules decrease. Although the precise mechanisms remain unknown, it is widely accepted that maternal–embryo communications, including embryonic signals, improve the receptive ability of the sex steroid hormone-primed endometrium. The embryo may utilize repulsive forces produced by an Eph–ephrin system for its timely attachment to and subsequent invasion through the endometrial epithelial layer. Importantly, the embryonic signals are considered to act on maternal immune cells to induce immune tolerance. They also elicit local inflammation that promotes endometrial differentiation and maternal tissue remodeling during embryo implantation and placentation. Additional clarification of the immune control mechanisms by embryonic signals, such as human chorionic gonadotropin, pre-implantation factor, zona pellucida degradation products, and laeverin, will aid in the further development of immunotherapy to minimize implantation failure in the future.

Integrative Analysis Revealing Human Adipose-Specific Genes and Consolidating Obesity Loci

Identification of adipose-specific genes has contributed to an understanding of mechanisms underlying adipocyte development and obesity. Herein, our analyses of the recent Genotype-Tissue Expression (GTEx) database revealed 38 adipose-specific/enhanced protein coding genes, among which 3 genes were novel adipose-specific, and 414 highly differentially expressed genes (DEGs) between subcutaneous and omental adipose depots. By integrative analyses of genome-wide association studies (GWASs), 14 adipose-specific/enhanced genes and 60 DEGs were found to be associated with obesity-related traits and diseases, consolidating evidence for contribution of these genes to the regional fat distribution and obesity phenotypes. In addition, expression of HOXC cluster was up-regulated in subcutaneous adipose tissue, and the majority of the HOXB cluster was expressed highly in omental adipose tissue, indicating differential expression patterns of HOX clusters in adipose depots. Our findings on the distinct gene expression profiles in adipose tissue and their relation to obesity provide an important foundation for future functional biological studies and therapeutic targets in obesity and associated diseases.

Involvement of Phenylalanine 297 in the Construction of the Substrate Pocket of Human Aminopeptidase B

Aminopeptidase B (APB, EC 3.4.11.6) preferentially hydrolyzes the N-terminal basic amino acids of synthetic and peptide substrates and requires a physiological concentration of NaCl for optimal activity. In this study, we used site-directed mutagenesis and molecular modeling to search for an amino acid residue that is critical for the enzymatic properties of human APB. Substitution of Phe297 with Tyr caused a significant decrease in hydrolytic activity toward synthetic and peptide substrates as well as chloride anion sensitivity. Molecular modeling suggests that Phe297 contributes to the construction of the substrate pocket of APB, which is wide enough to hold a chloride anion and allow the interaction of Gln169 with the N-terminal Arg residue of the substrate through bridging with the chloride anion. These results indicate that Phe297 is crucial for the optimal enzymatic activity and chloride anion sensitivity of APB via formation of the optimal structure of the catalytic pocket.

Epigenetic regulation of lncRNA connects ubiquitin-proteasome system with infection-inflammation in preterm births and preterm premature rupture of membranes

BACKGROUND

Preterm premature rupture of membranes (PPROM) is responsible for one third of all preterm births (PTBs). We have recently demonstrated that long noncoding RNAs (lncRNAs) are differentially expressed in human placentas derived from PPROM, PTB, premature rupture of the membranes (PROM), and full-term birth (FTB), and determined the major biological pathways involved in PPROM.

METHODS

Here, we further investigated the relationship of lncRNAs, which are differentially expressed in spontaneous PTB (sPTB) and PPROM placentas and are found to overlap a coding locus, with the differential expression of transcribed mRNAs at the same locus. Ten lncRNAs (five up-regulated and five down-regulated) and the lncRNA-associated 10 mRNAs (six up- and four down-regulated), which were identified by microarray in comparing PPROM vs. sPTB, were then validated by real-time quantitative PCR.

RESULTS

A total of 62 (38 up- and 24 down-regulated) and 1,923 (790 up- and 1,133 down-regulated) lncRNAs were identified from placentas of premature labor (sPTB + PPROM), as compared to those from full-term labor (FTB + PROM) and from premature rupture of membranes (PPROM + PROM), as compared to those from non-rupture of membranes (sPTB + FTB), respectively. We found that a correlation existed between differentially expressed lncRNAs and their associated mRNAs, which could be grouped into four categories based on the gene strand (sense or antisense) of lncRNA and its paired transcript. These findings suggest that lncRNA regulates mRNA transcription through differential mechanisms. Differential expression of the transcripts PPP2R5C, STAM, TACC2, EML4, PAM, PDE4B, STAM, PPP2R5C, PDE4B, and EGFR indicated a co-expression among these mRNAs, which are involved in the ubiquitine-proteasome system (UPS), in addition to signaling transduction and beta adrenergic signaling, suggesting that imbalanced regulation of UPS may present an additional mechanism underlying the premature rupture of membrane in PPROM.

CONCLUSION

Differentially expressed lncRNAs that were identified from the human placentas of sPTB and PPROM may regulate their associated mRNAs through differential mechanisms and connect the ubiquitin-proteasome system with infection-inflammation pathways. Although the detailed mechanisms by which lncRNAs regulate their associated mRNAs in sPTB and PPROM are yet to be clarified, our findings open a new approach to explore the pathogenesis of sPTB and PPROM.

Placental expression of aminopeptidase-Q (laeverin) and its role in the pathophysiology of preeclampsia

OBJECTIVE

The purpose of this study was to investigate the expression and subcellular localization of laeverin, a placenta-specific membrane-bound aminopeptidase, in preeclamptic placentas and its role in trophoblast cell migration and invasion.

STUDY DESIGN

Expression of laeverin was investigated in 6 normal and 6 preeclamptic placentas with the use of immunofluorescence, sodium dodecylsulfate-polyacrylamide gel electrophoresis with Western blot analysis and immunoelectron microscopy. The role of laeverin in trophoblast migration and invasion was studied with the use of the xCelligence system and Boyden chambers with Matrigel in HTR-8/SVneo cells. The effect of laeverin gene-silencing on selected genes that are involved in cell transformation and tumorigenesis was evaluated by polymerase chain reaction array. The Student t test, Mann-Whitney U test, χ(2) test, or F-test was used to compare groups as appropriate.

RESULTS

Laeverin was expressed in the cell membrane of villous trophoblasts in third-trimester healthy placentas; in preeclamptic placentas, it was expressed ectopically in the cytoplasm, especially in microvesicles. Immunoelectron microscopy showed laeverin leakage into the fetal capillaries and abundant expression in microvesicles in preeclamptic placentas. Migration and invasion of HTR-8/SVneo cells were reduced by 11.5% (P = .023) and 56.7% (P = .001), respectively, by laeverin gene-silencing. Analysis of downstream pathways affected by laeverin-silencing demonstrated significant down-regulation of integrin A2 (39-fold), integrin B3 (5-fold), and matrix metalloprotease 1 (36-fold).

CONCLUSION

Expression of laeverin protein is altered in preeclamptic placentas. Its ectopic expression in the cytoplasm and microvesicles, rather than the cell membrane and leakage into the fetal capillaries, may have a role in the pathophysiologic condition of preeclampsia. Laeverin gene appears to be involved in trophoblast cell migration and invasion through interaction with integrins and matrix metalloprotease 1.

Evolutionary analysis of the mammalian M1 aminopeptidases reveals conserved exon structure and gene death

The members of the M1 aminopeptidase family share conserved domains, yet show functional divergence within the family as a whole. In order to better understand this family, this study analyzed the mammalian members in depth at exon, gene, and protein levels. The twelve human members, eleven rat members, and eleven mouse members were first analyzed in multiple alignments to visualize both reported and unreported conserved domains. Phylogenetic trees were then generated for humans, rats, mice, and all mammals to determine how closely related the homologs were and to gain insight to the divergence in the family members. This produced three groups with similarity within the family. Next, a synteny study was completed to determine the present locations of the genes and changes that had occurred. It became apparent that gene death likely resulted in the lack of one member in mouse and rat. Finally, an in-depth analysis of the exon structure revealed that nine members of the human family and eight in mouse, are highly conserved within the exon structure. Taken together, these results indicate that the M1 aminopeptidase family is a divergent family with three subgroups and that genetic evidence mirrors categorization of the family by enzymatic function.

Modeling of human M1 aminopeptidases for in silico screening of potential Plasmodium falciparum alanine aminopeptidase (PfA-M1) specific inhibitors

Plasmodium falciparum alanine M1-aminopeptidase (PfA-M1) is a validated target for anti-malarial drug development. Presence of significant similarity between PfA-M1 and human M1-aminopeptidases, particularly within regions of enzyme active site leads to problem of non-specificity and off-target binding for known aminopeptidase inhibitors. Molecular docking based in silico screening approach for off-target binding has high potential but requires 3D-structure of all human M1-aminopeptidaes. Therefore, in the present study 3D structural models of seven human M1-aminopeptidases were developed. The robustness of docking parameters and quality of predicted human M1-aminopeptidases structural models was evaluated by stereochemical analysis and docking of their respective known inhibitors. The docking scores were in agreement with the inhibitory concentrations elucidated in enzyme assays of respective inhibitor enzyme combinations (r2≈0.70). Further docking analysis of fifteen potential PfA-M1 inhibitors (virtual screening identified) showed that three compounds had less docking affinity for human M1-aminopeptidases as compared to PfA-M1. These three identified potential lead compounds can be validated with enzyme assays and used as a scaffold for designing of new compounds with increased specificity towards PfA-M1.

Specifying and sustaining pigmentation patterns in domestic and wild cats

Color markings among felid species display both a remarkable diversity and a common underlying periodicity. A similar range of patterns in domestic cats suggests a conserved mechanism whose appearance can be altered by selection. We identified the gene responsible for tabby pattern variation in domestic cats as Transmembrane aminopeptidase Q (Taqpep), which encodes a membrane-bound metalloprotease. Analyzing 31 other felid species, we identified Taqpep as the cause of the rare king cheetah phenotype, in which spots coalesce into blotches and stripes. Histologic, genomic expression, and transgenic mouse studies indicate that paracrine expression of Endothelin3 (Edn3) coordinates localized color differences. We propose a two-stage model in which Taqpep helps to establish a periodic pre-pattern during skin development that is later implemented by differential expression of Edn3.

Characterization of a Vibrio fischeri aminopeptidase and evidence for its influence on an early stage of squid colonization

Vibrio fischeri cells are the sole colonists of a specialized light organ in the mantle cavity of the sepiolid squid Euprymna scolopes. The process begins when the bacteria aggregate in mucus secretions outside the light organ. The cells eventually leave the aggregate, enter the light organ, and encounter a rich supply of peptides. The need to dissociate from mucus and presumably utilize peptides led us to hypothesize that protease activity is integral to the colonization process. Protease activity associated with whole cells of Vibrio fischeri strain ES114 was identified as the product of a putative cell membrane-associated aminopeptidase (PepN). To characterize this activity, the aminopeptidase was cloned, overexpressed, and purified. Initial steady-state kinetic studies revealed that the aminopeptidase has broad activity, with a preference for basic and hydrophobic side chains and k(cat) and K(m) values that are lower and smaller, respectively, than those of Escherichia coli PepN. A V. fischeri mutant unable to produce PepN is significantly delayed in its ability to colonize squid within the first 12 h, but eventually it establishes a wild-type colonization level. Likewise, in competition with the wild type for colonization, the mutant is outcompeted at 12 h postinoculation but then competes evenly by 24 h. Also, the PepN-deficient strain fails to achieve wild-type levels of cells in aggregates, suggesting an explanation for the initial colonization delay. This study provides a foundation for more studies on PepN expression, localization, and role in the early stages of squid colonization.

Role of the Arabidopsis leucine aminopeptidase 2

Proteolysis-related genes have diverse functions across taxa and have long been considered as key players for intracellular protein turnover. Growing evidence indicates the biological significance of peptidases in degradation, maturation and modulation of bioactive peptides/proteins. By screening T-DNA tagged lines and functional analysis approaches we unraveled the Arabidopsis leucine aminopeptidase (AtLAP2) function in amino acid turnover. Transcriptomics and metabolomics profiling data suggested involvement of AtLAP2 in specific metabolic pathways. Loss-of-function of AtLAP2 resulted in early-leaf senescent and stress-sensitive phenotypes. Our work indicates an important in planta role for AtLAP2 contributing to a further understanding of the proteases having several implications in higher plants.

Mechanism of maternal vascular remodeling during human pregnancy

Remodeling of maternal spiral arteries by invasion of extravillous trophoblast (EVT) is crucial for an adequate blood supply to the fetus. EVT cells that migrate through the decidual tissue destroy the arterial muscular lining from the outside (interstitial invasion), and those that migrate along the arterial lumen displace the endothelium from the inside (endovascular invasion). Numerous factors including cytokines/growth factors, chemokines, cell adhesion molecules, extracellular matrix-degrading enzymes, and environmental oxygen have been proposed to stimulate or inhibit the differentiation/invasion of EVT. Nevertheless, it is still difficult to depict overall pictures of the mechanism controlling perivascular and endovascular invasion. Potential factors that direct interstitial trophoblast towards maternal spiral artery are relatively high oxygen tension in the spiral artery, maternal platelets, vascular smooth muscle cells, and Eph/ephrin system. On the other hand, very little is understood about endovascular invasion except for the involvement of endothelial apoptosis in this process. Only small numbers of molecules such as polysialylated neural cell adhesion molecules and CCR1 have been suggested as specific markers for the endovascular trophoblast. Therefore, an initial step to approach the mechanisms for endovascular invasion could be more detailed molecular characterization of the endovascular trophoblast.

Secretion of endoplasmic reticulum aminopeptidase 1 is involved in the activation of macrophages induced by lipopolysaccharide and interferon-gamma

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme with an important role in processing antigenic peptides presented to class I major histocompatibility complex in the endoplasmic reticulum. In this study, we found that endoplasmic reticulum-retained ERAP1 was secreted from macrophages in response to activation by treatment with lipopolysaccharide (LPS) and interferon (IFN)-γ and enhanced their phagocytic activity. Enhancement of the phagocytic activity of murine macrophage RAW264.7 cells induced by LPS/IFN-γ was inhibited by a potent aminopeptidase inhibitor, amastatin. The addition of recombinant wild-type but not inactive mutant ERAP1 to culture medium enhanced phagocytosis. These results suggest that enhancement of phagocytic activity is at least in part mediated by secreted ERAP1 through the generation of active peptides processed by the enzyme. Our data reveal ERAP1-mediated activation of macrophages for the first time and will provide new insights into the role of this enzyme in innate immunity.

Involvement of glutamine-238 in the substrate specificity of human laeverin/aminopeptidase Q

Human laeverin/aminopeptidase Q (APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of extravillous trophoblasts. In this study, we examined the significance of Gln-238 of laeverin/APQ, a putative S1 site residue, by site-directed mutagenesis for its enzymatic activity and substrate specificity. Replacement of Gln-238 with Ala caused a significant change in substrate specificity rather than a decrease in enzymatic activity. These results indicate that Gln-238 is important for the substrate specificity of laeverin/APQ. In addition, our data suggest that direct electrostatic interaction between substrate and S1 site of the enzyme is not involved in the mutant enzyme's preference for basic amino acids.

Histidine 379 of human laeverin/aminopeptidase Q, a nonconserved residue within the exopeptidase motif, defines its distinctive enzymatic properties

Human laeverin/aminopeptidase Q (LVRN/APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of human extravillous trophoblasts. Multiple sequence alignment of human M1 aminopeptidase revealed that the first Gly residue within the conserved exopeptidase motif of the M1 family, GXMEN motif, is uniquely substituted for His in human LVRN/APQ. In this study, we evaluated the roles of nonconserved His(379), comprising the exopeptidase motif in the enzymatic properties of human LVRN/APQ. We revealed that the substitution of His(379) with Gly caused significant changes in substrate specificity both toward fluorogenic substrates and natural peptide hormones. In addition, the susceptibilities of bestatin, a sensitive inhibitor for human LVRN/APQ, and natural inhibitory peptides were decreased in the H379G mutant. A molecular model suggested a conformational difference between wild-type and H379G human LVRN/APQs. These results indicate that His(379) of the enzyme plays essential roles in its distinctive enzymatic properties and contributes to maintaining the appropriate structure of the catalytic cavity of the enzyme. Our data may bring new insight into the biological significance of the unique exopeptidase motif of LVRN/APQ obtained during the evolution of primates.

A new type of neuron-specific aminopeptidase NAP-2 in rat brain synaptosomes

A novel neutral aminopeptidase (NAP-2) was found exclusively in the rat central nervous system (CNS). It was separated from the ubiquitous puromycin-sensitive aminopeptidase (PSA) and the neuron-specific aminopeptidase (NAP) by an automated FPLC-aminopeptidase analyzer. The activity of the neuronal aminopeptidase enriched in the synaptosomes is different from NAP and PSA in distribution and during brain development. The enzyme was purified 2230-fold to apparent homogeneity from rat brain cytosol with 4% recovery by ammonium sulfate fractionation, followed by column chromatography successively on Phenyl-Sepharose, Q-Sepharose, Sephadex G-200, and Mono Q. The single-chain enzyme with a molecular mass of 110kDa has an optimal pH of 7.0 and a pI of 5.6. It splits beta-naphthylamides of amino acid with aliphatic, polar uncharged, positively charged, and aromatic side chain. Leucyl beta-naphthylamide (Leu betaNA) is the best substrate with the highest hydrolytic coefficiency followed by Met betaNA=Arg betaNA=Lys betaNA>Ala betaNA>Tyr betaNA>Phe betaNA. The cysteine-, metallo-, glyco-aminopeptidase releases the N-terminal Tyr from Leu-enkephalin with a K(m) 82microM and a k(cat) of 1.08s(-1), and Met-enkephalin with a K(m) of 106microM and a k(cat) of 2.6s(-1). The puromycin-sensitive enzyme is most susceptible to amastatin with an IC(50) of 0.05microM. The data indicate that the enzyme is a new type of NAP found in rodent. Its possible function in neuron growth, neurodegeneration, and carcinomas is discussed.

The significance of brain aminopeptidases in the regulation of the actions of angiotensin peptides in the brain

From the outset, the concept of a brain renin-angiotensin system (RAS) has been controversial and this controversy continues to this day. In addition to the unresolved questions as to the means by which, and location(s) where brain Ang II is synthesized, and the uncertainties regarding the functionality of the different subtypes of Ang II receptors in the brain, a new controversy has arisen with respect to the identity of the angiotensin peptide(s) that activate brain AT(1) receptors. While it has been known for some time that Ang III can activate Ang II receptors with equivalent or near-equivalent efficacy to Ang II, it has been proposed that in the brain, only Ang III is active. This proposal, which we have named "The Angiotensin III Hypothesis" states that Ang II must be converted to Ang III in order to activate brain AT(1) receptors. This review examines several aspects of the controversies regarding the brain RAS with a special focus on brain aminopeptidases, studies that either support or refute The Angiotensin III Hypothesis, and the implications of The Angiotensin III Hypothesis for the activity of the brain RAS. It also addresses the need for further research that can test The Angiotensin III Hypothesis and definitively identify the angiotensin peptide(s) that activate brain AT(1) receptor-mediated effects.

Asparatic acid 221 is critical in the calcium-induced modulation of the enzymatic activity of human aminopeptidase A

Aminopeptidase A (APA) plays an important role in the regulation of blood pressure by mediating angiotensin II degradation in the renin-angiotensin system. The Ca2+-induced modulation of enzymatic activity is the most characteristic feature of APA among the M1 family of aminopeptidases. In this study, we used site-directed mutagenesis for any residues responsible for the Ca2+ modulation of human APA. Alignment of sequences of the M1 family members led to the identification of Asp-221 as a significant residue of APA among the family members. Replacement of Asp-221 with Asn or Gln resulted in a loss of Ca2+ responsiveness toward synthetic substrates. These enzymes were also unresponsive to Ca2+ when peptide hormones, such as angiotensin II, cholecystokinin-8, neurokinin B, and kallidin, were employed as substrates. These results suggest that the negative charge of Asp-221 is essential for Ca2+ modulation of the enzymatic activity of APA and causes preferential cleavage of acidic amino acid at the N-terminal end of substrate peptides.