Pregnancy-specific glycoprotein expression in normal gastrointestinal tract and in tumors detected with novel monoclonal antibodies

Activation of immune signals during organ transplantation

The activation of host's innate and adaptive immune systems can lead to acute and chronic graft rejection, which seriously impacts graft survival. Thus, it is particularly significant to clarify the immune signals, which are critical to the initiation and maintenance of rejection generated after transplantation. The initiation of response to graft is dependent on sensing of danger and stranger molecules. The ischemia and reperfusion of grafts lead to cell stress or death, followed by releasing a variety of damage-associated molecular patterns (DAMPs), which are recognized by pattern recognition receptors (PRRs) of host immune cells to activate intracellular immune signals and induce sterile inflammation. In addition to DAMPs, the graft exposed to 'non-self' antigens (stranger molecules) are recognized by the host immune system, stimulating a more intense immune response and further aggravating the graft damage. The polymorphism of MHC genes between different individuals is the key for host or donor immune cells to identify heterologous 'non-self' components in allogeneic and xenogeneic organ transplantation. The recognition of 'non-self' antigen by immune cells mediates the activation of immune signals between donor and host, resulting in adaptive memory immunity and innate trained immunity to the graft, which poses a challenge to the long-term survival of the graft. This review focuses on innate and adaptive immune cells receptor recognition of damage-associated molecular patterns, alloantigens and xenoantigens, which is described as danger model and stranger model. In this review, we also discuss the innate trained immunity in organ transplantation.

Perturbation of placental protein glycosylation by endoplasmic reticulum stress promotes maladaptation of maternal hepatic glucose metabolism

Placental hormones orchestrate maternal metabolic adaptations to support pregnancy. We hypothesized that placental ER stress, which characterizes early-onset pre-eclampsia (ePE), compromises glycosylation, reducing hormone bioactivity and these maladaptations predispose the mother to metabolic disease in later life. We demonstrate ER stress reduces the complexity and sialylation of trophoblast protein N-glycosylation, while aberrant glycosylation of vascular endothelial growth factor reduced its bioactivity. ER stress alters the expression of 66 of the 146 genes annotated with "protein glycosylation" and reduces the expression of sialyltransferases. Using mouse placental explants, we show ER stress promotes the secretion of mis-glycosylated glycoproteins. Pregnant mice carrying placentas with junctional zone-specific ER stress have reduced blood glucose, anomalous hepatic glucose metabolism, increased cellular stress and elevated DNA methyltransferase 3A. Using pregnancy-specific glycoproteins as a readout, we also demonstrate aberrant glycosylation of placental proteins in women with ePE, thus providing a mechanistic link between ePE and subsequent maternal metabolic disorders.

Recombinant pregnancy-specific glycoprotein-1-Fc reduces functional deficit in a mouse model of permanent brain ischaemia

Background

The well-characterised role of the immune system in acute ischaemic stroke has prompted the search for immunomodulatory therapies. Pregnancy-specific glycoproteins (PSGs) are a group of proteins synthesised by placental trophoblasts which show immunomodulatory properties. The aim of this study was to determine whether a proposed PSG1-based therapeutic enhanced recovery in a mouse model of brain ischaemia and to explore possible immunomodulatory effects.

Methods

Mice underwent permanent electrocoagulation of the left middle cerebral artery (pMCAO). They received saline (n = 20) or recombinant pregnancy-specific glycoprotein-1-alpha “fused” to the Fc domain of IgG1 (rPSG1-Fc) (100 μg) (n = 22) at 1 h post-ischaemia. At 3 and 5 days post-ischaemia, neurobehavioural recovery was assessed by the grid-walking test. At 5 days post-ischaemia, lesion size was determined by NeuN staining. Peripheral T cell populations were quantified via flow cytometry. Immunohistochemistry was used to quantify ICAM-1 expression and FoxP3+ cell infiltration in the ischaemic brain. Immunofluorescence was employed to determine microglial activation status via Iba-1 staining.

Results: rPSG1-Fc significantly enhanced performance in the grid-walking test at 3 and 5 days post-ischaemia. No effect on infarct size was observed. A significant increase in circulating CD4⁺ FoxP3+ cells and brain-infiltrating FoxP3+ cells was noted in rPSG1-Fc-treated mice. Among CD4⁺ cells, rPSG1-Fc enhanced the expression of IL-10 in spleen, blood, draining lymph nodes, and non-draining lymph nodes, while downregulating IFN-γ and IL-17 in spleen and blood. A similar cytokine expression pattern was observed in CD8⁺ cells. rPSG1-Fc reduced activated microglia in the infarct core.

Conclusion

The administration of rPSG1-Fc improved functional recovery in post-ischaemic mice without impacting infarct size. Improved outcome was associated with a modulation of the cytokine-secreting phenotype of CD4⁺ and CD8⁺ T cells towards a more regulatory phenotype, as well as reduced activation of microglia. This establishes proof-of-concept of rPSG1-Fc as a potential stroke immunotherapy.

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rPSG1-Fc enhances functional recovery in a mouse model of permanent brain ischaemia.

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rPSG1-Fc increases circulating CD4⁺ FoxP3+ cells and brain-infiltrating FoxP3+ cells.

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rPSG1-Fc increases the expression of IL-10 among CD4⁺ cells in spleen, blood, and lymph nodes.

Identification of KLF6/PSGs and NPY-Related USF2/CEACAM Transcriptional Regulatory Networks via Spinal Cord Bulk and Single-Cell RNA-Seq Analysis

Background

To further understand the development of the spinal cord, an exploration of the patterns and transcriptional features of spinal cord development in newborn mice at the cellular transcriptome level was carried out.

Methods

The mouse single-cell sequencing (scRNA-seq) dataset was downloaded from the GSE108788 dataset. Single-cell RNA-Seq (scRNA-Seq) was conducted on cervical and lumbar spinal V2a interneurons from 2 P0 neonates. Single-cell analysis using the Seurat package was completed, and marker mRNAs were identified for each cluster. Then, pseudotemporal analysis was used to analyze the transcription changes of marker mRNAs in different clusters over time. Finally, the functions of these marker mRNAs were assessed by enrichment analysis and protein-protein interaction (PPI) networks. A transcriptional regulatory network was then constructed using the TRRUST dataset.

Results

A total of 949 cells were screened. Single-cell analysis was conducted based on marker mRNAs of each cluster, which revealed the heterogeneity of neonatal mouse spinal cord neuronal cells. Functional analysis of pseudotemporal trajectory-related marker mRNAs suggested that pregnancy-specific glycoproteins (PSGs) and carcinoembryonic antigen cell adhesion molecules (CEACAMs) were the core mRNAs in cluster 3. GSVA analysis then demonstrated that the different clusters had differences in pathway activity. By constructing a transcriptional regulatory network, USF2 was identified to be a transcriptional regulator of CEACAM1 and CEACAM5, while KLF6 was identified to be a transcriptional regulator of PSG3 and PSG5. This conclusion was then validated using the Genotype-Tissue Expression (GTEx) spinal cord transcriptome dataset.

Conclusions

This study completed an integrated analysis of a single-cell dataset with the utilization of marker mRNAs. USF2/CEACAM1&5 and KLF6/PSG3&5 transcriptional regulatory networks were identified by spinal cord single-cell analysis.

BRAF mutations may identify a clinically distinct subset of glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. Prior studies examining the mutational landscape of GBM revealed recurrent alterations in genes that regulate the same growth control pathways. To this regard, ~ 40% of GBM harbor EGFR alterations, whereas BRAF variants are rare. Existing data suggests that gain-of-function mutations in these genes are mutually exclusive. This study was designed to explore the clinical, pathological, and molecular differences between EGFR- and BRAF-mutated GBM. We reviewed retrospective clinical data from 89 GBM patients referred for molecular testing between November 2012 and December 2015. Differences in tumor mutational profile, location, histology, and survival outcomes were compared in patients with EGFR- versus BRAF-mutated tumors, and microarray data from The Cancer Genome Atlas was used to assess differential gene expression between the groups. Individuals with BRAF-mutant tumors were typically younger and survived longer relative to those with EGFR-mutant tumors, even in the absence of targeted treatments. BRAF-mutant tumors lacked distinct histomorphology but exhibited unique localization in the brain, typically arising adjacent to the lateral ventricles. Compared to EGFR- and IDH1-mutant tumors, BRAF-mutant tumors showed increased expression of genes related to a trophoblast-like phenotype, specifically HLA-G and pregnancy specific glycoproteins, that have been implicated in invasion and immune evasion. Taken together, these observations suggest a distinct clinical presentation, brain location, and gene expression profile for BRAF-mutant tumors. Pending further study, this may prove useful in the stratification and management of GBM.

Expression of Pregnancy Specific β-1 Glycoprotein 1 in Cervical Cancer Cells

BACKGROUND

Cervical Cancer (CC) is a worldwide public health concern associated with genetic alterations, among these the gain of the 19q chromosome harboring the Pregnancy Specific Glycoproteins (PSG) gene family. These proteins play a critical role in pregnancy, with participation in immunotolerance, angiogenesis, and invasion processes, which are also observed in carcinogenesis. The aim of this study was to determine the molecular alterations of PSG1 and its relationship with CC.

METHODS

PSG1 Copy Number Variation (CNV) was evaluated in 31 CC and eight normal cervical tissues by qPCR. PSG1 expression was correlated with HPV detection and IL-10 and TGF-β expression in CC samples. Finally, PSG1 protein expression was evaluated by immunofluorescence in CC cell lines, by immunohistochemistry in a tissue microarray, and by immunoblotting in the sera of women with normal cervix, pre-invasive lesions, and CC.

RESULTS

PSG1 showed a gain of 25.6% in CNV and gene expression in CC. There was a lack of PSG1 expression in normal cervical epithelium and positive immunostaining in 57% of CC tissues, while all CC cell lines expressed PSG1. Finally, PSG1 was immunodetected in 90% of pre-invasive lesions and in all CC serum samples, but not in healthy women. PSG1 expression correlates with the expression of IL-10 and TGF-β in CC tissues, but not with the presence of HPV.

CONCLUSION

These data show evidence of the differential expression of PSG1 in CC that could explain its participation in tumor-biology and immunotolerance mechanisms. Further, its immunodetection could provide early detection of this cancer.

Interaction of Pregnancy-Specific Glycoprotein 1 With Integrin Α5β1 Is a Modulator of Extravillous Trophoblast Functions

Human pregnancy-specific glycoproteins (PSGs) serve immunomodulatory and pro-angiogenic functions during pregnancy and are mainly expressed by syncytiotrophoblast cells. While PSG mRNA expression in extravillous trophoblasts (EVTs) was reported, the proteins were not previously detected. By immunohistochemistry and immunoblotting, we show that PSGs are expressed by invasive EVTs and co-localize with integrin 5. In addition, we determined that native and recombinant PSG1, the most highly expressed member of the family, binds to 51 and induces the formation of focal adhesion structures resulting in adhesion of primary EVTs and EVT-like cell lines under 21% oxygen and 1% oxygen conditions. Furthermore, we found that PSG1 can simultaneously bind to heparan sulfate in the extracellular matrix and to 51 on the cell membrane. Wound healing assays and single-cell movement tracking showed that immobilized PSG1 enhances EVT migration. Although PSG1 did not affect EVT invasion in the in vitro assays employed, we found that the serum PSG1 concentration is lower in African-American women diagnosed with early-onset and late-onset preeclampsia, a pregnancy pathology characterized by shallow trophoblast invasion, than in their respective healthy controls only when the fetus was a male; therefore, the reduced expression of this molecule should be considered in the context of preeclampsia as a potential therapy.

Activation of latent transforming growth factor-β1, a conserved function for pregnancy-specific beta 1-glycoproteins

STUDY QUESTION

Do all 10 human pregnancy-specific beta 1-glycoproteins (PSGs) and murine PSG23 activate latent transforming growth factor-β1 (TGF-β1)?

SUMMARY ANSWER

All human PSGs and murine PSG23 activated latent TGF-β1.

WHAT IS KNOWN ALREADY

Two of the 10 members of the PSG1 family, PSG1 and PSG9, were previously shown to activate the soluble small latent complex of TGF-β1, a cytokine with potent immune suppressive functions.

STUDY DESIGN, SIZE, DURATION

Recombinant PSGs were generated and tested for their ability to activate the small latent complex of TGF-β1 in a cell-free ELISA-based assay and in a bioassay. In addition, we tested the ability of PSG1 and PSG4 to activate latent TGF-β bound to the extracellular matrix (ECM) or on the membranes of the Jurkat human T-cell line.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Recombinant PSGs were generated by transient transfection and purified with a His-Trap column followed by gel filtration chromatography. The purified PSGs were compared to vehicle (PBS) used as control for their ability to activate the small latent complex of TGF-β1. The concentration of active TGF-β was measured in an ELISA using the TGF-β receptor II as capture and a bioassay using transformed mink epithelial cells that express luciferase in response to active TGF-β. The specificity of the signal was confirmed using a TGF-β receptor inhibitor. We also measured the binding kinetics of some human PSGs for the latent-associated peptide (LAP) of TGF-β using surface plasmon resonance and determined whether PSG1 and PSG4 could activate the large latent complex of TGF-β1 bound to the ECM and latent TGF-β1 bound to the cell membrane. All experiments were performed in triplicate wells and repeated three times.

MAIN RESULTS AND THE ROLE OF CHANCE

All human PSGs activated the small latent complex of TGF-β1 (P < 0.05 vs. control) and showed similar affinities (KD) for LAP. Despite the lack of sequence conservation with its human counterparts, the ability to activate latent TGF-β1 was shared by a member of the murine PSG family. We found that PSG1 and PSG4 activated the latent TGF-β stored in the ECM (P < 0.01) but did not activate latent TGF-β1 bound to glycoprotein A repetitions predominant (GARP) on the surface of Jurkat T cells.

LIMITATIONS, REASONS FOR CAUTION

The affinity of the interaction of LAP and PSGs was calculated using recombinant proteins, which may differ from the native proteins in their post-translational modifications. We also utilized a truncated form of murine PSG23 rather than the full-length protein. For the studies testing the ability of PSGs to activate membrane-bound TGF-β1, we utilized the T-cell line Jurkat and Jurkat cells expressing GARP rather than primary T regulatory cells. All the studies were performed in vitro.

WIDER IMPLICATIONS OF THE FINDINGS

Here, we show that all human PSGs activate TGF-β1 and that this function is conserved in at least one member of the rodent PSG family. In vivo PSGs could potentially increase the availability of active TGF-β1 from the soluble and matrix-bound latent forms of the cytokine contributing to the establishment of a tolerogenic environment during pregnancy.

LARGE-SCALE DATA

None.

STUDY FUNDING/COMPETING INTEREST(S)

The research was supported by a grant from the Collaborative Health Initiative Research Program (CHIRP). No conflicts of interests are declared by the authors.

Recombinant Pregnancy-Specific Glycoprotein 1 Has a Protective Role in a Murine Model of Acute Graft-versus-Host Disease

Acute graft-versus-host disease (aGVHD) is an immune-mediated reaction that can occur after hematopoietic stem cell transplantation in which donor T cells recognize the host antigens as foreign, destroying host tissues. Establishment of a tolerogenic immune environment while preserving the immune response to infectious agents is required for successful bone marrow transplantation. Pregnancy-specific glycoprotein 1 (PSG1), which is secreted by the human placenta into the maternal circulation throughout pregnancy, likely plays a role in maintaining immunotolerance to prevent rejection of the fetus by the maternal immune system. We have previously shown that PSG1 activates the latent form of transforming growth factor β1 (TGF-β), a cytokine essential for the differentiation of tolerance-inducing CD4⁺FoxP3⁺ regulatory T cells (Tregs). Consistent with this observation, treatment of naïve murine T cells with PSG1 resulted in a significant increase in FoxP3⁺ cells that was blocked by a TGF-β receptor I inhibitor. We also show here that PSG1 can increase the availability of active TGF-β in vivo. As the role of CD4⁺FoxP3⁺ cells in the prevention of aGVHD is well established, we tested whether PSG1 has beneficial effects in a murine aGHVD transplantation model. PSG1-treated mice had reduced numbers of tissue-infiltrating inflammatory CD3⁺ T cells and had increased expression of FoxP3 in T cells compared with vehicle-treated mice. In addition, administration of PSG1 significantly inhibited aGVHD-associated weight loss and mortality. On the other hand, administration of PSG1 was less effective in managing aGVHD in the presence of an alloimmune reaction against a malignancy in a graft-versus-leukemia experimental model. Combined, this data strongly suggests that PSG1 could be a promising treatment option for patients with aGVHD following bone marrow transplantation for a nonmalignant condition, such as an autoimmune disorder or a genetic immunodeficiency.

Mutual Interplay between the Human Cytomegalovirus Terminase Subunits pUL51, pUL56, and pUL89 Promotes Terminase Complex Formation

Human cytomegalovirus (HCMV) genome encapsidation requires several essential viral proteins, among them pUL56, pUL89, and the recently described pUL51, which constitute the viral terminase. To gain insight into terminase complex assembly, we investigated interactions between the individual subunits. For analysis in the viral context, HCMV bacterial artificial chromosomes carrying deletions in the open reading frames encoding the terminase proteins were used. These experiments were complemented by transient-transfection assays with plasmids expressing the terminase components. We found that if one terminase protein was missing, the levels of the other terminase proteins were markedly diminished, which could be overcome by proteasome inhibition or providing the missing subunit in trans These data imply that sequestration of the individual subunits within the terminase complex protects them from proteasomal turnover. The finding that efficient interactions among the terminase proteins occurred only when all three were present together is reminiscent of a folding-upon-binding principle leading to cooperative stability. Furthermore, whereas pUL56 was translocated into the nucleus on its own, correct nuclear localization of pUL51 and pUL89 again required all three terminase constituents. Altogether, these features point to a model of the HCMV terminase as a multiprotein complex in which the three players regulate each other concerning stability, subcellular localization, and assembly into the functional tripartite holoenzyme.IMPORTANCE HCMV is a major risk factor in immunocompromised individuals, and congenital CMV infection is the leading viral cause for long-term sequelae, including deafness and mental retardation. The current treatment of CMV disease is based on drugs sharing the same mechanism, namely, inhibiting viral DNA replication, and often results in adverse side effects and the appearance of resistant virus strains. Recently, the HCMV terminase has emerged as an auspicious target for novel antiviral drugs. A new drug candidate inhibiting the HCMV terminase, Letermovir, displayed excellent potency in clinical trials; however, its precise mode of action is not understood yet. Here, we describe the mutual dependence of the HCMV terminase constituents for their assembly into a functional terminase complex. Besides providing new basic insights into terminase formation, these results will be valuable when studying the mechanism of action for drugs targeting the HCMV terminase and developing additional substances interfering with viral genome encapsidation.

Pregnancy Specific β-1 Glycoprotein 1 is Expressed in Pancreatic Ductal Adenocarcinoma and its Subcellular Localization Correlates with Overall Survival

Proteins of the pregnancy specific β-1 glycoprotein (PSG) family are renowned for their elevated expression during pregnancy. Only few reports have investigated their expression in adenocarcinomas. We studied the expression of PSG1 in pancreatic adenocarcinoma (PDAC). In a cohort of 104 patient samples, immunohistochemical analysis determined PSG1 expression in every specimen. PSG1 was found at apical and cytoplasmic localization or solely at cytoplasmic localization, with the latter case being correlated to shortened median survival (25 vs 11 months, logrank p-value < 0.001). At the same time, enzyme linked immunosorbent assay (ELISA) did not detect elevated PSG1 levels in the plasma of PDAC patients as opposed to the plasma of healthy, non-pregnant control individuals. We also probed the impact of PSG1 expression in a murine tumor model system, using subcutaneous injection of Colo-26 cells into immunocompetent BALB/c mice. Here, tumor growth was not affected by the expression of human PSG1. Our study reaffirms interest into the tumor-contextual biology of PSG proteins.