Low-density Lipoprotein Receptor Class Research Articles

Novel Peptide DR3penA as a Low-Toxicity Antirenal Fibrosis Agent by Suppressing the TGF-β1/miR-212-5p/Low-Density Lipoprotein Receptor Class a Domain Containing 4/Smad Axis.

Renal fibrosis is a complex pathological process that contributes to the development of chronic kidney disease due to various risk factors. Conservative treatment to curb progression without dialysis or renal transplantation is widely applicable, but its effectiveness is limited. Here, the inhibitory effect of the novel peptide DR3penA (DHα-(4-pentenyl)-AlaNPQIR-NH2), which was developed by our group, on renal fibrosis was assessed in cells and mice with established fibrosis and fibrosis triggered by transforming growth factor-β1 (TGF-β1), unilateral ureteral obstruction, and repeated low-dose cisplatin. DR3penA preserved renal function and ameliorated renal fibrosis at a dose approximately 100 times lower than that of captopril, which is currently used in the clinic. DR3penA also significantly reduced existing fibrosis and showed similar efficacy after subcutaneous or intraperitoneal injection. Mechanistically, DR3penA repressed TGF-β1 signaling via miR-212-5p targeting of low-density lipoprotein receptor class a domain containing 4, which interacts with Smad2/3. In addition to having good pharmacological effects, DR3penA could preferentially target injured kidneys and exhibited low toxicity in acute and chronic toxicity experiments. These results unveil the advantages of DR3penA regarding efficacy and toxicity, making it a potential candidate compound for renal fibrosis therapy.

LDLa containing C-type lectin mediates phagocytosis of V.anguillarum and regulates immune effector genes in shrimp

C-type lectins (CTLs) function as pattern recognition receptors (PRRs) by recognizing invading microorganisms, thereby triggering downstream immune events against infected pathogens. In this study, a novel CTL containing a low-density lipoprotein receptor class A (LDLa) domain was obtained from Litopenaeus vannamei, designed as LvLDLalec. Stimulation by the bacterial pathogen Vibrio anguillarum (V. anguillarum) resulted in remarkable up-regulation of LvLDLalec, as well as release of LvLDLalec into hemolymph. The rLvLDLalec protein possessed broad-spectrum bacterial binding and agglutinating activities, as well as hemocyte attachment ability. Importantly, LvLDLalec facilitated the bacterial clearance in shrimp hemolymph and protected shrimp from bacterial infection. Further studies revealed that LvLDLalec promoted hemocytes phagocytosis against V. anguillarum and lysosomes were involved in the process. Meanwhile, LvLDLalec participated in humoral immunity through activating and inducing nuclear translocation of Dorsal to regulate phagocytosis-related genes and antimicrobial peptides (AMPs) genes, thereby accelerated the removal of invading pathogens in vivo and improved the survival rate of L. vannamei. These results unveil that LvLDLalec serves as a PRR participate in cellular and humoral immunity exerting opsonin activity to play vital roles in the immune regulatory system of L. vannamei.

Entry receptor LDLRAD3 is required for Venezuelan equine encephalitis virus peripheral infection and neurotropism leading to pathogenesis in mice

Venezuelan equine encephalitis virus (VEEV) is an encephalitic alphavirus responsible for epidemics of neurological disease across the Americas. Low-density lipoprotein receptor class A domain-containing 3 (LDLRAD3) is a recently reported entry receptor for VEEV. Here, using wild-type and Ldlrad3-deficient mice, we define a critical role for LDLRAD3 in controlling steps in VEEV infection, pathogenesis, and neurotropism. Our analysis shows that LDLRAD3 is required for efficient VEEV infection and pathogenesis prior to and after central nervous system invasion. Ldlrad3-deficient mice survive intranasal and intracranial VEEV inoculation and show reduced infection of neurons in different brain regions. As LDLRAD3 is a determinant of pathogenesis and an entry receptor required for VEEV infection of neurons of the brain, receptor-targeted therapies may hold promise as countermeasures.

Mutations in atypical hemolytic uremic syndrome provide evidence for the role of calcium in complement factor I

AbstractAtypical hemolytic uremic syndrome (aHUS) is a rare thrombotic microangiopathy. Genetic variants in complement proteins are found in ≈60% of patients. Of these patients, ≈15% carry mutations in complement factor I (CFI). Factor I (FI) is a multidomain serine protease that cleaves and thereby inactivates C3b and C4b in the presence of cofactor proteins. Crystal structures have shown that FI possesses 2 calcium-binding domains, low-density lipoprotein receptor class A (LDLRA) 1 and LDLRA2. Yet, the role of calcium in FI is unknown. We determined that 9 genetic variants identified in aHUS (N151S, G162D, G188A, V230E, A240G, G243R, C247G, A258T, and Q260D) cluster around the calcium-binding site of LDLRA1. Using site-directed mutagenesis, we established that the synthesis of all, except A258T, was impaired, implying defective protein folding, perhaps due to loss of calcium binding. To further explore this possibility, we generated 12 alanine mutants that coordinate with the calcium in LDLRA1 and LDLRA2 (K239A, D242A, I244A, D246A, D252A, E253A, Y276A, N279A, E281A, D283A, D289A, and D290A) and are expected to perturb calcium binding. Except for K239A and Y276A, none of the mutants was secreted. These observations suggest that calcium ions play key structural and functional roles in FI.

The entry receptor LDLRAD3 is critical for Venezuelan equine encephalitis virus pathogenesis and neuroinvasion in mice

Abstract Alphaviruses are enveloped positive-stranded RNA viruses of the Togaviridae family. Venezuelan equine encephalitis virus (VEEV) is an encephalitic alphavirus responsible for epidemics in equine and human populations across the Americas. Its potential for use as an aerosolized bioterrorism weapon and the demonstrated risk it poses in research settings highlight the need for countermeasures. VEEV pathogenesis is characterized by a systemic inflammatory response and central nervous system (CNS) infection, which can result in severe neurological complications and sequelae. Our laboratory identified a novel entry receptor for VEEV, low-density lipoprotein receptor class A domain containing 3 (LDLRAD3). Ldlrad3 −/−mice demonstrate reduced, but not abrogated, VEEV infection in target tissues and are resistant to disease and lethality. Here we define a critical role for LDLRAD3 in controlling VEEV tissue tropism and pathogenesis by studying the kinetics of infection in wild-type and Ldlrad3 −/−mice. Using detailed analyses of viral RNA levels, immunohistochemistry, flow cytometry, and primary neuronal cultures, we observed that VEEV infects LDLRAD3-expressing cell types as early as 6 h after inoculation and once in the CNS, preferentially targets neurons, and not glial cells, in a LDLRAD3-dependent manner. Overall, our studies define the role of LDLRAD3 in VEEV tropism and how LDLRAD3-dependent infection of LDLRAD3 contributes to the host inflammatory responses against VEEV. Finally, our studies demonstrate LDLRAD3-independent infection in Ldlrad3 −/−mice, which suggests the existence of alternate receptors for VEEV. These findings may be relevant for the generation of novel receptor-targeted antiviral therapies. NIAID F30AI164842

The relaxin receptor RXFP1 signals through a mechanism of autoinhibition.

The relaxin family peptide receptor 1 (RXFP1) is the receptor for relaxin-2, an important regulator of reproductive and cardiovascular physiology. RXFP1 is a multi-domain G protein-coupled receptor (GPCR) with an ectodomain consisting of a low-density lipoprotein receptor class A (LDLa) module and leucine-rich repeats. The mechanism of RXFP1 signal transduction is clearly distinct from that of other GPCRs, but remains very poorly understood. In the present study, we determine the cryo-electron microscopy structure of active-state human RXFP1, bound to a single-chain version of the endogenous agonist relaxin-2 and the heterotrimeric Gs protein. Evolutionary coupling analysis and structure-guided functional experiments reveal that RXFP1 signals through a mechanism of autoinhibition. Our results explain how an unusual GPCR family functions, providing a path to rational drug development targeting the relaxin receptors.

Gonad transcriptome analysis reveals the differences in gene expression related to sex-biased and reproduction of clam Cyclina sinensis

Sexual differentiation and gonad development are important biological processes for bivalve species. The clam Cyclina sinensis is an important cultured marine bivalve widely distributed along with the coastal areas of China. However, the information related to sexual determination/differentiation and gonadal development of C. sinensis almost has no reported. To study the molecular mechanisms of its sexual determination/differentiation and gonadal development, transcriptome analysis was performed in the gonad of C. sinensis, and the potential biological functions of reproduction-related gene were also investigated in this study. The results showed that 1 013 and 427 genes were differentially expressed in the ovary and testis, respectively. KEGG enrichment analysis showed that the DEGs in the gonad were significantly clustered in progesterone-mediated oocyte maturation, cell cycle and oocyte meiosis. Further analysis showed that 23 genes were mainly involved in sex determination/differentiation, including Dmrt1, Sox2/4/9, Foxl2, β-catenin and GATA-type zinc finger protein 1-like. Twenty key genes were mainly involved in the process of spermatogenesis, and five genes encode steroid biosynthesis and metabolism. Fifteen genes related to ovarian development were also identified in this study, such as Vitellogenin, MAM and LDL-receptor class A domain-containing protein 1 and Cell division cycle protein 20 homolog. Moreover, 50µg/L estradiol treatment significantly up-regulated the expression levels of CsVg in the ovary and hepatopancreas. These results highlight the genes involved in sexual determination/differentiation and gonadal development, which enhance our understanding for further studies of reproduction and breeding of C. sinensis and other marine bivalves.

Synthesis of multi-module low density lipoprotein receptor class A domains with acid labile cyanopyridiniumylides (CyPY) as aspartic acid masking groups.

Low-density lipoprotein receptor class A domains (LA modules) are common ligand-binding domains of transmembrane receptors of approximately 40 amino acids that are involved in several cellular processes including endocytosis of extracellular targets. Due to their wide-ranging function and distribution among different transmembrane receptors, LA modules are of high interest for therapeutic applications. However, the efficient chemical synthesis of LA modules and derivatives is hindered by complications, many arising from the high abundance of aspartic acid and consequent aspartimide formation. Here, we report a robust, efficient and general applicable chemical synthesis route for accessing such LA modules, demonstrated by the synthesis and folding of the LA3 and LA4 modules of the low-density lipoprotein receptor, as well as a heterodimeric LA3-LA4 constructed by chemical ligation. The synthesis of the aspartic acid-rich LA domain peptides is made possible by the use of cyanopyridiniumylides (CyPY) - reported here for the first time - as a masking group for carboxylic acids. We show that cyanopyridiniumylide masked aspartic acid monomers are readily available building blocks for solid phase peptide synthesis and successfully suppress aspartimide formation. Unlike previously reported ylide-based carboxylic acid protecting groups, CyPY protected aspartic acids are converted to the free carboxylic acid by acidic hydrolysis and are compatible with all common residues and protecting groups. The chemical synthesis of Cys- and Asp-rich LA modules enables new access to a class of difficult to provide, but promising protein domains.

A mechanistic analysis of bacterial recognition and serine protease cascade initiation in larval hemolymph of Manduca sexta

Serine protease cascades have evolved in vertebrates and invertebrates to mediate rapid defense responses. Previous biochemical studies showed that in hemolymph of a caterpillar, Manduca sexta, recognition of fungi by β-1,3-glucan recognition proteins (βGRP1 and βGRP2) or recognition of bacteria by peptidoglycan recognition protein-1 (PGRP1) and microbe binding protein (MBP) results in autoactivation of hemolymph protease-14 precursor (proHP14). HP14 then activates downstream members of a protease cascade leading to the melanization immune response. ProHP14 has a complex domain architecture, with five low-density lipoprotein receptor class A repeats at its amino terminus, followed by a Sushi domain, a Sushi domain variant called Wonton, and a carboxyl-terminal serine protease catalytic domain. Its zymogen form is activated by specific proteolytic cleavage at the amino-terminal end of the protease domain. While a molecular mechanism for recognition and triggering the response to β-1,3-glucan has been delineated, it is unclear how bacterial recognition stimulates proHP14 activation. To fill this knowledge gap, we expressed the two domains of M. sexta MBP and found that the amino-terminal domain binds to diaminopimelic acid-peptidoglycan (DAP-PG). ProHP14 bound to both the carboxyl-terminal domain (MBP-C) and amino-terminal domain (MBP-N) of MBP. In the mixture of DAP-PG, MBP, and larval plasma, inclusion of an HP14 fragment composed of LDLa repeats 2–5 (LDLa2–5) or MBP-C significantly reduced prophenoloxidase activation, likely by competing with the interactions of the full-length proteins, and suggesting that molecular interactions involving these regions of proHP14 and MBP take part in proHP14 activation in response to peptidoglycan. Using a series of N-terminally truncated versions of proHP14, we found that autoactivation required LDLa2–5. The optimal ratio of PGRP1, MBP, and proHP14 is close to 3:2:1. In summary, proHP14 autoactivation by DAP-type peptidoglycan requires binding of DAP-PG by PGRP1 and the MBP N-terminal domain and association of the LDLa2–5 region of proHP14 with the MBP C-terminal domain. These interactions may concentrate the proHP14 zymogen at the bacterial cell wall surface and promote autoactivation.

TMPRSS13 zymogen activation, surface localization, and shedding is regulated by proteolytic cleavage within the non-catalytic stem region.

TMPRSS13 is a member of the type II transmembrane serine protease (TTSP) family. Here we characterize a novel post-translational mechanism important for TMPRSS13 function: proteolytic cleavage within the extracellular TMPRSS13 stem region located between the transmembrane domain and the first site of N-linked glycosylation at asparagine (N)-250 in the scavenger receptor cysteine rich (SRCR) domain. Importantly, the catalytic competence of TMPRSS13 is essential for stem region cleavage, suggesting an autonomous mechanism of action. Site-directed mutagenesis of the 10 basic amino acids (four arginine and six lysine residues) in this region abrogated zymogen activation and catalytic activity of TMPRSS13, as well as phosphorylation, cell surface expression, and shedding. Mutation analysis of individual arginine residues identified R223, a residue located between the low-density lipoprotein receptor class A domain and the SRCR domain, as important for stem region cleavage. Mutation of R223 causes a reduction in the aforementioned functional processing steps of TMPRSS13. These data provide further insight into the roles of different post-translational modifications as regulators of the function and localization of TMPRSS13. Additionally, the data suggest the presence of complex interconnected regulatory mechanisms that may serve to ensure the proper levels of cell-surface and pericellular TMPRSS13-mediated proteolysis under homeostatic conditions.

L-Arabinose improves hypercholesterolemia via regulating bile acid metabolism in high-fat-high-sucrose diet-fed mice

BackgroundHypercholesterolemia is closely associated with an increased risk of cardiovascular diseases. l-Arabinose exhibited hypocholesterolemia properties, but underlying mechanisms have not been sufficiently investigated. This study aimed to elucidate the mechanisms of l-arabinose on hypocholesterolemia involving the enterohepatic circulation of bile acids.MethodsThirty six-week-old male mice were randomly divided into three groups: the control group and the high-fat-high-sucrose diet (HFHSD)-fed group were gavaged with distilled water, and the l-arabinose-treated group were fed HFHSD and received 400 mg/kg/day l-arabinose for 12 weeks. Serum and liver biochemical parameters, serum and fecal bile acid, cholesterol and bile acid metabolism-related gene and protein expressions in the liver and small intestine were analyzed.Resultsl-Arabinose supplementation significantly reduced body weight gain, lowered circulating low-density lipoprotein cholesterol (LDL-C) while increasing high-density lipoprotein cholesterol (HDL-C) levels, and efficiently alleviated hepatic inflammation and lipid accumulations in HFHSD-fed mice. l-Arabinose inhibited cholesterol synthesis via downregulation of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). Additionally, l-arabinose might facilitate reverse cholesterol transport, evidenced by the increased mRNA expressions of low-density lipoprotein receptor (LDL-R) and scavenger receptor class B type 1 (SR-B1). Furthermore, l-arabinose modulated ileal reabsorption of bile acids mainly through downregulation of ileal bile acid-binding protein (I-BABP) and apical sodium-dependent bile acid transporter (ASBT), resulting in the promotion of hepatic synthesis of bile acids via upregulation of cholesterol-7α-hydroxylase (CYP7A1).Conclusionsl-Arabinose supplementation exhibits hypocholesterolemic effects in HFHSD-fed mice primarily due to regulation of bile acid metabolism-related pathways.

Human Placental Intracellular Cholesterol Transport: A Focus on Lysosomal and Mitochondrial Dysfunction and Oxidative Stress.

The placenta participates in cholesterol biosynthesis and metabolism and regulates exchange between the maternal and fetal compartments. The fetus has high cholesterol requirements, and it is taken up and synthesized at elevated rates during pregnancy. In placental cells, the major source of cholesterol is the internalization of lipoprotein particles from maternal circulation by mechanisms that are not fully understood. As in hepatocytes, syncytiotrophoblast uptake of lipoprotein cholesterol involves lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SR-BI). Efflux outside the cells requires proteins such as the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. However, mechanisms associated with intracellular traffic of cholesterol in syncytiotrophoblasts are mostly unknown. In hepatocytes, uptaken cholesterol is transported to acidic late endosomes (LE) and lysosomes (LY). Proteins such as Niemann–Pick type C 1 (NPC1), NPC2, and StAR related lipid transfer domain containing 3 (STARD3) are required for cholesterol exit from the LE/LY. These proteins transfer cholesterol from the lumen of the LE/LY into the LE/LY-limiting membrane and then export it to the endoplasmic reticulum, mitochondria, or plasma membrane. Although the production, metabolism, and transport of cholesterol in placental cells are well explored, there is little information on the role of proteins related to intracellular cholesterol traffic in placental cells during physiological or pathological pregnancies. Such studies would be relevant for understanding fetal and placental cholesterol management. Oxidative stress, induced by generating excess reactive oxygen species (ROS), plays a critical role in regulating various cellular and biological functions and has emerged as a critical common mechanism after lysosomal and mitochondrial dysfunction. This review discusses the role of cholesterol, lysosomal and mitochondrial dysfunction, and ROS in the development and progression of hypercholesterolemic pregnancies.

The Role of FGF19 and MALRD1 in Enterohepatic Bile Acid Signaling.

Bile acids are the catabolic end products of cholesterol metabolism that are best known for their role in the digestion of lipids. In the last two decades, extensive investigation has shown bile acids to be important signaling molecules in metabolic processes throughout the body. Bile acids are ligands that can bind to several receptors, including the nuclear receptor farnesoid X receptor (FXR) in ileal enterocytes. FXR activation induces the expression of fibroblast growth factor (FGF) 15/19, a hormone that can modulate bile acid levels, repress gluconeogenesis and lipogenesis, and promote glycogen synthesis. Recent studies have described a novel intestinal protein, MAM and LDL Receptor Class A Domain containing 1 (MALRD1) that positively affects FGF15/19 levels. This signaling pathway presents an exciting target for treating metabolic disease and bile acid-related disorders.

CD320 expression and apical membrane targeting in renal and intestinal epithelial cells

Vitamin B12 is an essential nutrient acquired via dietary intake. Receptor-mediated endocytosis is a key mechanism in vitamin B12 absorption, cellular uptake, and reabsorption. CD320 is a type I transmembrane protein responsible for cellular uptake of vitamin B12 in peripheral tissues. In this study, we examined segmental distribution and cellular expression of CD320 in mouse kidneys and intestines. We show that CD320 is expressed on the luminal surface in the small intestine and in proximal tubules in the kidney, suggesting that, in addition to its role in vitamin B12 uptake in peripheral tissues, CD320 may participate in vitamin B12 absorption in the small intestine and reabsorption in the kidney. Moreover, we show that an amino acid motif, DSSDE, in the second low-density lipoprotein receptor class A domain of CD320 is a key apical membrane targeting signal in both renal and intestinal epithelial cells. Mutations or deletion of this motif abolish the specific apical membrane expression of CD320 in polarized Madin–Darby canine kidney cells and human colon cancer-derived Caco-2 cells. In short-hairpin RNA-based gene knockdown experiments, we show that the apical membrane targeting of CD320 is mediated by a Rab11a-dependent mechanism. These results extend our knowledge regarding the cell biology of CD320 and its role in vitamin B12 metabolism.

Structure of Venezuelan equine encephalitis virus with its receptor LDLRAD3.

Venezuelan equine encephalitis virus (VEEV) is an enveloped RNA virus that causes encephalitis and potentially mortality in infected humans and equines1. At present, no vaccines or drugs are available that prevent or cure diseases caused by VEEV. Low-density lipoprotein receptor class A domain-containing 3 (LDLRAD3) was recently identified as a receptor for the entry of VEEV into host cells2. Here we present the cryo-electron microscopy structure of the LDLRAD3 extracellular domain 1 (LDLRAD3-D1) in complex with VEEV virus-like particles at a resolution of 3.0 Å. LDLRAD3-D1 has a cork-like structure and is inserted into clefts formed between adjacent VEEV E2-E1 heterodimers in the viral-surface trimer spikes through hydrophobic and polar contacts. Mutagenesis studies of LDLRAD3-D1 identified residues that are involved in the key interactions with VEEV. Of note, some of the LDLRAD3-D1 mutants showed a significantly increased binding affinity for VEEV, suggesting that LDLRAD3-D1 may serve as a potential scaffold for the development of inhibitors of VEEV entry. Our structures provide insights into alphavirus assembly and the binding of receptors to alphaviruses, which may guide the development of therapeutic countermeasures against alphaviruses.

Circ_0006988 promotes the proliferation, metastasis and angiogenesis of non-small cell lung cancer cells by modulating miR-491-5p/MAP3K3 axis

ABSTRACT Circular RNAs (circRNAs) are related to the progression of non-small cell lung cancer (NSCLC). However, the roles and mechanism of circ_0006988 are largely unknown. The levels of circ_0006988, Low-Density Lipoprotein Receptor Class A Domain Containing 3 (LDLRAD3), microRNA-491-5p (miR-491-5p), Mitogen-Activated Protein Kinase Kinase Kinase 3 (MAP3K3) were measured using quantitative real-time polymerase-chain reaction (qRT-PCR) and western blot assay. The characteristic of circ_0006988 was analyzed by RNase R assay and Actinomycin D assay. Functional analyses were processed by Cell Counting Kit-8 (CCK-8) assay, 5-ethynyl-2ʹ-deoxyuridine (EdU) assay, colony formation assay, flow cytometry analysis, transwell assay, wound-healing assay and tube formation assay. The interactions between circ_0006988 and miR-491-5p as well as miR-491-5p and MAP3K3 were analyzed by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Murine xenograft model assay was processed to verify the function of circ_0006988 in vivo. Immunohistochemistry (IHC) assay was conducted to examine the level of Ki67. Circ_0006988 abundance was increased in NSCLC tissues and cells. Circ_0006988 silencing restrained NSCLC cell proliferation, migration, invasion and angiogenesis, and induced apoptosis. Circ_0006988 sponged miR-491-5p, which directly targeted MAP3K3. MiR-491-5p overexpression repressed NSCLC cell malignant behaviors. MiR-491-5p downregulation or MAP3K3 overexpression reversed the effect of circ_0006988 silencing on NSCLC cell progression. In addition, circ_0006988 knockdown reduced xenograft tumor growth. ssCirc_0006988 contributed to the development of NSCLC by miR-491-5p/MAP3K3 axis.

RNA interference-mediated functional characterization of Group I chitin deacetylases in Holotrichia parallela Motschulsky

Chitin deacetylases (CDAs, EC 3.5.1.41) catalyze the N-deacetylation of chitin to produce chitosan, which is essential for insect survival. Hence, CDAs are promising targets for the development of novel insecticidal drugs. In this study, the putative Group I chitin deacetylase genes HpCDA1, HpCDA2-1 and HpCDA2-2 were identified from Holotrichia parallela. Conserved domain database search identified a chitin-binding peritrophin-A domain (ChBD), a low-density lipoprotein receptor class A domain (LDLa), and a putative CDA-like catalytic domain. RT-qPCR analysis showed that the Group I HpCDAs were expressed in various tissues and predominant in the integument. The developmental expression patterns from the first-instar to third-instar larvae showed that HpCDAs were highly expressed on the first day and gradually declined after molting. The functional characteristics of the Group I CDAs in cuticle organization were examined using RNA interference (RNAi) and transmission electron microscopy (TEM) methods. Administration of double-stranded HpCDA (dsHpCDA) through larval injection could suppress the expression levels of HpCDA1 and HpCDA2, thus resulting in abnormal or lethal phenotypes. TEM analysis revealed that RNAi of either HpCDA1 or HpCDA2 remarkably affected the cuticle integrity, as evidenced by cuticle disorganization and chitin laminae disruption, suggesting the crucial role of CDAs in chitin modification. These experimental results demonstrate the important contribution of putative key genes involved in chitin metabolism, and provide a foundation for developing new strategies to control H. parallela.

LDLRAD2 promotes pancreatic cancer progression through Akt/mTOR signaling pathway.

Low-density lipoprotein receptor class A domain containing 2 (LDLRAD2) acts as a protein-coding gene in a large number of human diseases. However, the potential roles and underlying mechanism in pancreatic cancer remains unclear. Therefore, this study was conducted to address this question. Herein, we found that the expression of LDLRAD2 was elevated in pancreatic cancer tissues and cell lines. LDLRAD2 knockdown inhibited pancreatic cancer cell proliferation, migration, and invasion in vitro. Besides, silencing LDLRAD2 impaired tumor growth and metastasis in vivo and up-regulated the E-Cadherin level, whereas down-regulated the expression of N-Cadherin and Vimentin levels, which indicating that LDLRAD2 knockdown suppresses EMT. Additionally, LDLRAD2 knockdown decreased the Warburg effect and glycolytic enzymes expression. Pathway scan assay and western blotting assay indicated that LDLRAD2 knockdown significantly down-regulated the expression of phosphorylation of Akt and phosphorylation of mTOR, which suggested that knockdown of LDLRAD2 inhibits Akt/mTOR signaling pathway. Taken together, these findings suggested that LDLRAD2 may be an oncogene in pancreatic cancer via modulating Akt/mTOR signaling pathway.

A novel G protein-coupled receptor for starfish gonadotropic hormone, relaxin-like gonad-stimulating peptide.

Gonadotropic hormones play important regulatory roles in reproduction. Relaxin-like gonad-stimulating peptide (RGP) is a gonadotropin-like hormone in starfish. However, a receptor for RGP remains to be identified. Here, we describe the identification of an authentic receptor for RGP (RGPR) in the starfish, Patiria pectinifera. A binding assay using radioiodinated P. pectinifera RGP (PpeRGP) revealed that RGPR was expressed in ovarian follicle cells. A RGPR candidate was identified by homology-searching of transcriptome data of P. pectinifera follicle cells. Based on the contig sequences, a putative 947-amino acid PpeRGPR was cloned from follicle cells. Like the vertebrate relaxin family peptide receptors (RXFP 1 and 2), PpeRGPR was a G protein-coupled receptor that harbored a low-density lipoprotein-receptor class A motif and leucine-rich repeat sequences in the extracellular domain of the N-terminal region. Sf9 cells transfected with Gαq16-fused PpeRGPR activated calcium ion mobilization in response to PpeRGP, but not to RGP of another starfish Asterias amurensis, in a dose-dependent fashion. These results confirmed the species-specific reactivity of RGP and the cognate receptor. Thus, the present study provides evidence that PpeRGPR is a specific receptor for PpeRGP. To the best of our knowledge, this is the first report on the identification of a receptor for echinoderm RGP.

LDLRAD3 is a receptor for Venezuelan equine encephalitis virus.

Venezuelan equine encephalitis virus (VEEV) is a mosquito-transmitted neurotropic alphavirus that causes encephalitis and death in humans1. VEEV is a biodefense concern because of its potential for aerosol spread and lack of sufficient countermeasures. The host factors required for VEEV entry and infection remain poorly characterized. Using a genome-wide CRISPR/Cas9-based screen, we identify Ldlrad3, a highly conserved member of the scavenger receptor superfamily, as a receptor for VEEV. Gene editing of mouse Ldlrad3 or human LDLRAD3 results in markedly reduced viral infection of neuronal cells, which is restored upon complementation. Ldlrad3 binds directly to VEEV particles and enhances virus attachment and internalization into cells. Genetic studies indicate that domain 1 (D1) of Ldlrad3 is necessary and sufficient to support VEEV infection, and both anti-Ldlrad3 antibodies and a Ldlrad3-D1-Fc fusion protein block VEEV infection in cell culture. Remarkably, VEEV pathogenesis is abrogated in mice with deletions in Ldlrad3, and administration of Ldlrad3-D1-Fc abolishes disease caused by multiple VEEV subtypes including highly virulent strains. The development of a decoy receptor fusion protein creates a strategy for preventing severe VEEV infection and disease in humans.