Fragmentation stability and retention time-shift obtained by LC-MS/MS to distinguish sialylated N-glycan linkage isomers in therapeutic glycoproteins

Sialylated N-glycan isomers withα2-3 orα2-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cytotoxic T lymphocyte-associated antigen-4-immunoglobulin(CTLA4-Ig),were produced in Chinese hamster ovary cell lines;however,their linkage isomers have not been reported.In this study,N-glycans of CTLA4-Igs were released,labeled with procainamide,and analyzed by liquid chromatography-tandem mass spectrometry(MS/MS)to identify and quantify sialylated N-glycan linkage isomers.The linkage isomers were distinguished by comparison of 1)intensity of the N-acetylglucosamine ion to the sialic acid ion(Ln/Nn)using different fragmentation stability in MS/MS spectra and 2)retention time-shift for a selective m/z value in the extracted ion chromatogram.Each isomer was distinctively identified,and each quantity(>0.1%)was obtained relative to the total N-glycans(100%)for all observed ionization states.Twenty sialylated N-glycan isomers with onlyα2-3 linkage(s)in WT were identified,and each isomer's sum of quantities was 50.4%.Furthermore,39 sialylated N-glycan isomers(58.8%)in mono-(3 N-glycans;0.9%),bi-(18;48.3%),tri-(14;8.9%),and tetra-(4;0.7%)antennary structures of mutant were obtained,which comprised mono-(15 N-glycans;25.4%),di-(15;28.4%),tri-(8;4.8%),and tetra-(1;0.2%)sialylation,respectively,with onlyα2-3(10 N-glycans;4.8%),bothα2-3 andα2-6(14;18.4%),and onlyα2-6(15;35.6%)linkage(s).These results are consistent with those forα2-3 neuraminidase-treated N-glycans.This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.

Acrosome reaction： relevance of zona pellucida glycoproteins

During mammalian fertilisation, the zona pellucida （ZP） matrix surrounding the oocyte is responsible for the binding of the spermatozoa to the oocyte and induction of the acrosome reaction （AR） in the ZP-bound spermatozoon. The AR is crucial for the penetration of the ZP matrix by spermatozoa. The ZP matrix in mice is composed of three glycoproteins designated ZP1, ZP2 and ZP3, whereas in humans, it is composed of four （ZP1, ZP2, ZP3 and ZP4）. ZP3 acts as the putative primary sperm receptor and is responsible for AR induction in mice, whereas in humans （in addition to ZP3）, ZP1 and ZP4 also induce the AR. The ability of ZP3 to induce the AR resides in its C-terminal fragment. O-linked glycans are critical for the murine ZP3-mediated AR. However, N-linked glycans of human ZP1, ZP3 and ZP4 have important roles in the induction of the AR. Studies with pharmacological inhibitors showed that the ZP3-induced AR involves the activation of the Gi-coupled receptor pathway, whereas ZP1- and ZP4-mediated ARs are independent of this pathway. The ZP3-induced AR involves the activation of T-type voltage-operated calcium channels （VOCCs）, whereas ZP1- and ZP4-induced ARs involve both T- and L-type VOCCs. To conclude, in mice, ZP3 is primarily responsible for the binding of capacitated spermatozoa to the ZP matrix and induction of the AR, whereas in humans （in addition to ZP3）, ZP1 and ZP4 also participate in these stages of fertilisation.

Glycoproteins and glycoproteomics in pancreatic cancer

Aberrations in protein glycosylation and polysaccharides play a pivotal role in pancreatic tumorigenesis, influencing cancer progression, metastasis, immunoresponse and chemoresistance. Abnormal expression in sugar moieties can impact the function of various glycoproteins, including mucins, surface receptors, adhesive proteins, proteoglycans, as well as their effectors and binding ligands, resulting in an increase in pancreatic cancer invasiveness and a cancerfavored microenvironment. Recent advance in glycoproteomics, glycomics and other chemical biology techniques have been employed to better understand the complex mechanism of glycosylation events and how they orchestrate molecular activities in genomics, proteomics and metabolomics implicated in pancreatic adenocarcinoma. A variety of strategies have been demonstrated targeting protein glycosylation and polysaccharides for diagnostic and therapeutic development.

Effect of Xiaoyu Zhixue Tablet (消瘀止血片) on Expression ofPlatelet Membrane Glycoproteins in Patients withHemorrhagic Thrombopathy

Objective: To observe the effect of Xiaoyu Zhixue tablet (消瘀止血片,XYZXT) on the expression of platelet membrane glycoproteins in patients with hemorrhagic thrombopathy, and to explore its possible mechanism. Methods: The total of 148 patients with hemorrhagic thrombopathy were randomly divided into two groups, the traditional Chinese medicicne (TCM) group (n=98) treated with XYZXT and the Western medicine (WM) group (n=50) treated with adrenosin, vitamins C, K and P, both for 6 months. The therapeutic effect and the recovery rate of platelet aggregation in the two groups were observed. And platelet membrane glycoprotein (GP) Ⅰb/Ⅸ, GPⅡb/Ⅲa complexes, GPⅠb, GPⅡb, GP Ⅲa and P-selectin were analyzed by flow cytometry in both groups before and after treatment and also in 34 normal healthy subjects. Results: The total effective rate of hemostasis was 89. 8% in TCM group and 54. 0% in the WM group (x2=45.83, P<0.01), and the recovery rate of platelet aggregation was 72.4% and 4.0% respectively (x2=62.06, P<0.01). The fluorescence intensity of GP Ⅰ b/Ⅸ, GPⅡb/Ⅲa complexes, GPⅠb, GPⅢa and P-selectin were lower in both groups before treatment than those in the healthy subjects. Expression of above-mentioned marks was elevated in TCM group after 6 months' therapy, which was insignificantly different as compared with the healthy subjects (P>0.05) and higher than those in the WM group (P<0.05). Conclusion: One of the mechanisms in treating hemorrhagic thrombopathy with XYZXT is that it could regulate the expression of GP Ⅰb/Ⅸ, GPⅡ b/Ⅲa complexes, GPⅠb, GPⅢa and P-selectin at the level of receptor protein.

Pregnancy-associated glycoproteins as a potential marker for diagnosis of earlypregnancy in goats: A scoping reviewing

Early diagnosis of pregnancy plays an important role to minimize reproductive losses in farm animals.There are several methods for pregnancy diagnosis like profiling of reproductive hormones(such as progesterone and estrone sulfate),but sometimes they provide false-positive results.Embryo specific pregnancy markers,which delineate the presence and viability of the embryo,are considered as perfect for pregnancy determination.Pregnancy-associated glycoproteins are distinguished as the best indicator for the determination of early pregnancy,fetal number,and birth weight of kids.Pregnancy-associated glycoproteins are structurally correlated to aspartic proteinase and are communicated in the external epithelial cell layer of the placenta.They have been found to share about half amino acid sequence identity with pepsinogen,pepsin,cathepsin D and E.Dislike different individuals from aspartic proteinase family,numerous pregnancy-associated glycoproteins appear to be latent compound as a result of amino acid substitutions in and around the catalytic site.This review is to discuss the scope and prospects of pregnancy-associated glycoproteins as a pregnancy marker in farm animals,more specifically in goats.

Clinical impact of hepatitis B and C virus envelope glycoproteins

Chronic infection by either hepatitis B virus(HBV)or hepatitis C virus(HCV)share epidemiological characteristics with risks for development of severe complications such as liver cirrhosis and hepatocellular carcinoma.HBV and HCV also share a high genetic variability. Among highly variable regions,viral genes encoding surface proteins(hepatitis B surface antigen,E1/E2 HCV glycoproteins)play key roles in the stimulation of the host-related immune response and viral entry into hepatocytes.Specific segments of HBV envelope proteins(preS1,"a"determinant)are crucial in the entry process into permissive cells.HCV entry is a complex multistep process involving multiple cell cofactors (glycosaminoglycans,low density lipoprotein receptor, SR-B1,CD81,claudin-1,occludin,EGFR,EphA2)in the interaction with HCV E1/E2 envelope glycoproteins.In vitro both viruses can be controlled by antibody-me-diated neutralization targeting viral envelope,also essential in preventing HBV infection in vivo as observed through successful vaccination using HBs antigen.But preventive vaccination and/or therapeutic pressure can influence HBV and HCV variability.For HBV,the patterns of antiviral drug resistance in chronic hepatitis are complex and the original pol/S gene overlap has to be taken into account.Treatment-induced HBV mutations in pol could indeed generate S mutants with subsequent modified antigenicity or increased cancer induction.Variability of HBV and HCV envelope proteins combining high exposure to selective pressures and crucial functional roles require investigation in the context of diagnostic,vaccination and treatment tools.In this editorial a synthesis is performed of HBV and HCV envelope properties at the entry step and as antigenic proteins,and the subsequent clinical impact.

N-glycans released from glycoproteins using a commercial kit and comprehensively analyzed with a hypothetical database

The glycosylation of proteins is responsible for their structural and functional roles in many cellular activities.This work describes a strategy that combines an efficient release, labeling and liquid chromatography–mass spectral analysis with the use of a comprehensive database to analyze N-glycans. The analytical method described relies on a recently commercialized kit in which quick deglycosylation is followed by rapid labeling and cleanup of labeled glycans. This greatly improves the separation, mass spectrometry（MS） analysis and fluorescence detection of N-glycans. A hypothetical database, constructed using Glyc Resoft, provides all compositional possibilities of N-glycans based on the common sugar residues found in N-glycans. In the initial version this database contains ＆gt; 8,700 N-glycans, and is compatible with MS instrument software and expandable. N-glycans from four different well-studied glycoproteins were analyzed by this strategy. The results provided much more accurate and comprehensive data than that had been previously reported. This strategy was then used to analyze the N-glycans present on the membrane glycoproteins of gastric carcinoma cells with different degrees of differentiation. Accurate and comprehensive N-glycan data from those cells was obtained efficiently and their differences were compared corresponding to their differentiation states. Thus, the novel strategy developed greatly improves accuracy, efficiency and comprehensiveness of N-glycan analysis.

Understanding the Glycoproteins Release from Alginate-Barium Capsules in Physiologic Enviroments

The authors carried out a steady and unsteady mass transfer studies to simulate both the release of proteins in physiologic environments and proteins transport through a tissue or organ from polymeric capsules by using a substance, the rhodamine B isothiocyanate dextran (RBID) that mimics the behaviour of glycoproteins such as vascular endothelial growth factor (VEFG). These studies highlighted the importance of electrostatic interactions between alginate and proteins in the release processes. Thereby, this fact has opened new perspectives in order to use these kind of capsules in protein recognition processes. The electrostatic interactions between alginate and RBID allow pH-dependent controlled release systems that simulate the behaviour of glycoproteins.

Purifi cation, characterization and hypoglycemic activity of glycoproteins obtained from pea (Pisum sativum L.)

This study aimed to isolate and characterize the structures of glycoproteins from peas and determine their hypoglycemic activity.The crude pea glycoproteins(PGP)were extracted by hot water and purified by diethylaminoethyl(DEAE)-Sepharose chromatography and Sephadex G-100 size-exclusion chromatography in sequence.Then three main fractions were obtained,namely PGP1,PGP2 and PGP3,with molecular weights of 897615,846740 and 1194692 Da,respectively.The physical and chemical properties of the three fractions were evaluated and compared by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(NMR),scanning electron microscope(SEM),high performance liquid chromatography(HPLC)and other analytical techniques.The fraction PGP2 with the highest hypoglycemic activity,was screened using the Caco-2 monolayer cell model.It can inhibit the uptake of glucose in the small intestine,as well as the activities of maltase and sucrase.After simulated gastrointestinal digestion,PGP2 signifi cantly enhanced the inhibitory effect of α-glucosidase,and slightly reduced the inhibitory ability ofα-amylase.In summary,PGP2 possessed strong hypoglycemic activity after digestion.These results indicated that PGP2 has the potential to be developed into a functional food or natural medicine for the treatment of type 2 diabetes mellitus.

Specifically Binding of L-ficolin to N-glycans of HCV Envelope Glycoproteins E1 and E2 Leads to Complement Activation

L-ficolin, one of lectin families, is a recently identified complement factor that initiates lectin pathway of complement. Little is known about its role in viral hepatitis. In the present study, we found that L-ficolin in serum from 103 patients with hepatitis C virus （HCV）, were significantly higher than that in 150 healthy controls. We further found that L-ficolin expressions were significantly increased in vitro study by HCV JFH-1 infected human hepatocyte cell line Huh7.5.1. Investigation of the mechanisms of the L-ficolin action on HCV demonstrated that L-ficolin protein could recognize and bind to envelope glycoproteins E1 and E2 of HCV, activating the lectin complement pathway-mediated cytolytic activity in HCV-infected hepatocyte. This interaction between L-ficolin and HCV E1 and E2 glycoproteins was attributed to the N-glycans of E1 and E2. These findings provide new insights into the biological functions of L-ficolin in clinically important hepatic viral diseases.

Application of magnetic solid phase extraction in separation and enrichment of glycoproteins and glycopeptides

The analysis of endogenous glycoproteins and glycopeptides in human body fluids is of great importance for screening and discovering disease biomarkers with clinical significance.However,the presence of interfering substances makes the direct quantitative detection of low-abundance glycoproteins and glycopeptides in human body fluids one of the great challenges in analytical chemistry.Magnetic solid phase extraction(MSPE)has the advantages of easy preparation,low cost and good magnetic responsiveness.Magnetic adsorbents are the core of MSPE technology,and magnetic adsorbents based on different functional materials are widely used in the quantitative analysis of glycoproteins and glycopeptides in human body fluids,making it possible to analyze glycoproteins and glycopeptides with low abundance as well as multiple types,which provides a technical platform for screening and evaluating glycoproteins and glycopeptides in body fluids as disease biomarkers.In this paper,we focus on the recent advances in the application of MSPE technology and magnetic adsorbents for the separation and enrichment of glycoproteins and glycopeptides in human body fluids,and the future trends and application prospects in this field are also presented.

Disentangling brain PrP^(C)proteoforms and their roles in physiology and disease

The cellular prion protein(PrPC),a cell surface glycoprotein of 209 amino acids,has been considerably studied over the decades mainly due to its critical involvement in transmissible spongiform encephalopathies,or prion diseases.Indeed,it is the misfolding and aggregation of PrPC into pathological assemblies-named PrPSc-that constitute prions,the agents causing these unusual neurodegenerative diseases affecting humans and animals(Prusiner,1982).Furthermore,increasing evidence support its relevance also in other neurodegenerative diseases(NDDs),such as Alzheimer’s and Parkinson’s diseases(Corbett et al.,2020).

Non-pancreatic hyperlipasemia:A puzzling clinical entity

BACKGROUND Increased lipase level is a serological hallmark of the diagnosis of acute pancreatitis(AP)but can be detected in various other diseases associated with lipase leakage due to inflammation of organs surrounding the pancreas or reduced renal clearance and/or hepatic metabolism.This non-pancreatic hyperlipasemia(NPHL)is puzzling for attending physicians during the diagnostic procedure for AP.It would be clinically beneficial to identify the clinical and laboratory variables that hinder the accuracy of lipase diagnosis with the aim of improve it.A more precise description of the NPHL condition could potentially provide prognostic factors for adverse outcomes which is currently lacking.AIM To perform a detailed clinical and laboratory characterization of NPHL in a large prospective patient cohort with an assessment of parameters determining disease outcomes.METHODS A Hungarian patient cohort with serum lipase levels at least three times higher than the upper limit of normal(ULN)was prospectively evaluated over 31 months.Patients were identified using daily electronic laboratory reports developed to support an ongoing observational,multicenter,prospective cohort study called the EASY trial(ISRCTN10525246)to establish a simple,easy,and accurate clinical scoring system for early prognostication of AP.Diagnosis of NPHL was established based on≥3×ULN serum lipase level in the absence of abdominal pain or abdominal imaging results characteristic of pancreatitis.RESULTS A total of 808 patients[male,n=420(52%);median age(IQR):65(51-75)years]were diagnosed with≥3×ULN serum lipase levels.A total of 392 patients had AP,whereas 401 had NPHL with more than 20 different etiologies.Sepsis and acute kidney injury(AKI)were the most prevalent etiologies of NPHL(27.7%and 33.2%,respectively).The best discriminative cut-off value for lipase was≥666 U/L(sensitivity,71.4%;specificity,88.8%).The presence of AKI or sepsis negatively affected the diagnostic performance of lipase.NPHL was associated with a higher in-hospital mortality than AP(22.4%vs 5.1%,P<0.001).In multivariate binary logistic regression,not lipase but increased amylase level(>244 U/L)and neutrophil-to-lymphocyte ratio(NLR)(>10.37,OR:3.71,95%CI:2.006-6.863,P<0.001),decreased albumin level,age,and presence of sepsis were independent risk factors for in-hospital mortality in NPHL.CONCLUSION NPHL is a common cause of lipase elevation and is associated with high mortality rates.Increased NLR value was associated with the highest mortality risk.The presence of sepsis/AKI significantly deteriorates the serological differentiation of AP from NPHL.

Comparison of macular changes according to the etiology of optic neuritis:a cross-sectional study

AIM:To compare the macular structure including foveal thickness among patients with optic neuritis(ON)according to the etiology and to investigate the possible correlation between structural and visual outcomes METHODS:In this retrospective cross-sectional study,the clinical data of patients with aquaporin-4 immunoglobulin G-related ON(AQP4 group,40 eyes),myelin oligodendrocyte glycoprotein IgG-related ON(MOG group,31 eyes),and multiple sclerosis-related ON(MS group,24 eyes)were obtained.The retinal thickness of the foveal,parafoveal and perifoveal regions were measured.Visual acuity(VA),visual field index and mean deviation were measured as visual outcomes.RESULTS:The AQP4 group showed a significantly thinner fovea(226.4±13.4μm)relative to the MOG(236.8±14.0μm,P=0.015)and MS(238.9±14.3μm,P=0.007)groups.The thickness in the parafoveal area also was thinner in the AQP4 group,though the difference in perifoveal retinal thickness was not significant.Foveal thickness was correlated with VA in the AQP4 group(coefficientρ=-0.418,P=0.014),but not in the MOG and MS groups(P=0.218 and P=0.138,respectively).There was no significant correlation between foveal thickness and visual field test in all three groups.CONCLUSION:The significant thinning in the fovea and parafoveal areas in the AQP4 group compared to the MOG and MS groups are found.Additionally,macular changes in AQP4-ON show a significant correlation with VA.The results provide the possibility that retinal structural damage could reflect functional damage in AQP4-ON,distinct from MOGON and MS-ON.

Biomarkers for neuromyelitis optica:a visual analysis of emerging research trends

Neuromyelitis optica is an inflammatory demyelinating disease of the central nervous system that differs from multiple sclerosis.Over the past 20 years,the search for biomarke rs for neuromyelitis optica has been ongoing.Here,we used a bibliometric approach to analyze the main research focus in the field of biomarkers for neuromyelitis optica.Research in this area is consistently increasing,with China and the United States leading the way on the number of studies conducted.The Mayo Clinic is a highly reputable institution in the United States,and was identified as the most authoritative institution in this field.Furthermore,Professor Wingerchuk from the Mayo Clinic was the most authoritative expe rt in this field.Keyword analysis revealed that the terms "neuro myelitis optica"(261 times), "multiple sclerosis"(220 times), "neuromyelitis optica spectrum disorder"(132 times), "aquaporin4"(99 times),and "optical neuritis"(87 times) were the most frequently used keywords in literature related to this field.Comprehensive analysis of the classical literature showed that the majority of publications provide conclusive research evidence supporting the use of aquaporin-4-IgG and neuromyelitis optica-IgG to effectively diagnose and differentiate neuromyelitis optica from multiple sclerosis.Furthermore,aquaporin-4-IgG has emerged as a highly specific diagnostic biomarker for neuromyelitis optica spectrum disorder.Myelin oligodendrocyte glycoprotein-IgG is a diagnostic biomarke r for myelin oligodendrocyte glycoprotein antibody-associated disease.Recent biomarkers for neuromyelitis optica in clude cerebrospinal fluid immunological biomarkers such as glial fibrillary acidic protein,serum astrocyte damage biomarkers like FAM19A5,serum albumin,and gammaaminobutyric acid.The latest prospective clinical trials are exploring the potential of these biomarkers.Preliminary results indicate that glial fibrillary acidic protein is emerging as a promising candidate biomarker for neuromyelitis optica spectrum disorder.The ultimate goal of future research is to identify non-invasive biomarkers with high sensitivity,specificity,and safety for the accurate diagnosis of neuro myelitis optica.

Boronic acid-containing carbon dots array for sensitive identification of glycoproteins and cancer cells

Discrimination of glycoproteins and cell types is a significant but difficult issue.Herein,we presented a novel fluorescence sensor array for the detection and identification of glycoproteins and cancer cells based on the specific affinity between boronic acid-containing carbon dots(BA-CDs)and cis-diol residues of polysaccharides.The differential binding affinity of three BA-CDs to various glycoproteins resulted in a different fluorescence turn-on signal pattern caused by aggregation-enhanced emission(AEE),along with negligible response from other proteins.Therefore,BA-CDs encompassing sensing elements and signal indicator into one can enable a fast and accurate discrimination of glycoproteins with simple and easy operation.Seven glycoproteins could be well discriminated at a very low concentration of 10 nmol/L.The discriminating capability of glycoproteins is not sacrificed in both human urine and serum.Notably,different glycoprotein compositions of cancer cells provide more recognizable features for identification of cancer cells,comparing to the total protein.Five cell types could be identified in 15 min at a low concentration of 1000 cells/mL.This method is fast,accurate,and easy operation,and has a potential application in cancer diagnosis.

Computer-designed orthogonal RNA aptamers programmed to recognize Ebola virus glycoproteins

Ebola virus (EBOV), a member of the filovirus family, is an enveloped negative-sense RNA virus that causes lethal infections in humans and primates. Thousands of people have died from the Ebola virus disease (EVD) in West Africa, and no specific antiviral medication and treatment have been approved for EVD. Although the development of an EBOV vaccine is promising, immunity to any vaccine is not immediate. Here, we computationally analysed the structure of EBOV glycoprotein GP2 (GP2EBOV) and designed RNA aptamers that recognize and inhibit it. The aptamers specifically bind to conserved arginine residues (Arg587 and Arg596) located in the C-terminal coiled-coil region of GP2EBOV. Molecular docking of the synthetic RNA aptamers with the ectodomain of GP2EBOV revealed that the optimized orthogonal RNA aptamers have strong binding affinities with the coiled-coil region of GP2EBOV. The characterized RNA aptamers may facilitate strategies to block replication of EBOV and related Filoviruses, and thus may serve as important antivirals to reduce mortality associated with these infections.

Improving Baculovirus Transduction of Mammalian Cells by Incorporation of Thogotovirus Glycoproteins

Baculovirus can transduce a wide range of mammalian cells and is considered a promising gene therapy vector. However,the low transduction efficiency of baculovirus into many mammalian cells limits its practical application. Co-expressing heterologous viral glycoproteins(GPs), such as vesicular stomatitis virus G protein(VSV G), with baculovirus native envelope protein GP64 is one of the feasible strategies for improving virus transduction. Tick-borne thogotoviruses infect mammals and their GPs share sequence/structure homology and common evolutionary origins with baculovirus GP64.Herein, we tested whether thogotovirus GPs could facilitate the entry of the prototype baculovirus Autographa californica multiple multiple nucleopolyhedrovirus(AcMNPV) into mammalian cells. The gp genes of two thogotoviruses, Thogoto virus and Dhori virus, were inserted into the AcMNPV genome. Both GPs were properly expressed and incorporated into the envelope of the recombinant AcMNPVs. The transduction rates of recombinant AcMNPVs expressing the two thogotovirus GPs increased for approximately 4–12 fold compared to the wild type AcMNPV in six of the 12 tested mammalian cell lines. It seemed that thogotovirus GPs provide the recombinant AcMNPVs with different cell tropisms and showed better performance in several mammalian cells compared to VSV G incorporated AcMNPV. Further studies showed that the improved transduction was a result of augmented virus-endosome fusion and endosome escaping, rather than increased cell binding or internalization. We found the AcMNPV envelope protein GP64-mediated fusion was enhanced by the thogotovirus GPs at relatively higher p H conditions. Therefore, the thogotovirus GPs represent novel candidates to improve baculovirus-based gene delivery vectors.

Recent advances in the study of active endogenous retrovirus envelope glycoproteins in the mammalian placenta

Endogenous retroviruses(ERVs) are a component of the vertebrate genome and originate from exogenous infections of retroviruses in the germline of the host. ERVs have coevolved with their hosts over millions of years. Envelope glycoproteins of endogenous retroviruses are often expressed in the mammalian placenta, and their potential function has aroused considerable research interest, including the manipulation of maternal physiology to benefit the fetus. In most mammalian species, trophoblast fusion in the placenta is an important event, involving the formation of a multinucleated syncytiotrophoblast layer to fulfill essential fetomaternal exchange functions. The key function in this process derives from the envelope genes of endogenous retroviruses, namely syncytins, which show fusogenic properties and placenta-specific expression. This review discusses the important role of the recognized endogenous retrovirus envelope glycoproteins in the mammalian placenta.

VARIATIONS OF LECTIN-BINDING GLYCOPROTEINS IN EARLY PREGNANT RABBIT EMBRYO

In the present study, the quantitative and qualitative changes of three kinds of lectinbinding glycoproteins of early pregnant rabbit embryos (D4—D12) were analyzed. The technique of Western blot, as well as video densitometer scanning and its analytic software was used for analysis. Results found that there were five specific lectin-binding glycoproteins in Day 4 to Day 6 blastocyst fluids: one ConA-binding glycoprotein about 70 kD, two WGA-binding glycoproteins respectively about 42 kD and 25kD and two PNA-binding glycoprotein respectively about 180kD and 75kD. They disappeared immediately after implan tation, It is demonstrated that there are stage-specific glycoproteins in rabbit blastocyst fluid which might be relevant to the recognition of pregnancy and implantation.