Micafungin exerts antitumor effect on breast cancer and osteosarcoma through preventing EMT in tumor cells in an USP7/AKT/GSK-3ß pathway-dependent manner.

Breast cancer and osteosarcoma are common cancers in women and children, respectively, but ideal drugs for treating patients with breast cancer or osteosarcoma remain to be found. Micafungin is an antifungal drug with antitumor activity on leukemia. Based on the notion of drug repurposing, this study aims to evaluate the antitumor effects of micafungin on breast cancer and osteosarcoma in vitro and in vivo, and to elucidate the underlying mechanisms. Five breast cancer cell lines (MDA-MB-231, BT-549, SK-BR-3, MCF-7, and 4T1) and one osteosarcoma cell line (143B) were chosen for the in vitro studies. Micafungin exerted an inhibitory effect on the viability of all cell lines, and MCF-7 cells were most sensitive to micafungin among the breast cancer cell lines. In addition, micafungin showed an inhibitory effect on the proliferation, clone formation, and migration in MCF7 and 143B cells. The inhibitory effect of micafungin on the growth of breast cancer and osteosarcoma was further confirmed with xenograft tumor mouse models. To explore the underlying mechanisms, the effect of micafungin on epithelial-mesenchymal transition (EMT) was examined. As expected, the levels of matrix metalloproteinase 9 and vimentin in MCF-7 and 143B cells were notably reduced in the presence of micafungin, concomitant with the decreased levels of ubiquitin-specific protease 7 (USP7), p-AKT, and p-GSK-3ß. Based on these observations, we conclude that micafungin exerts antitumor effect on breast cancer and osteosarcoma through preventing EMT in an USP7/AKT/GSK-3ß pathway-dependent manner.

Role of Hippocampal miR-132-3p in Modifying the Function of Protein Phosphatase Mg2+/Mn2+-dependent 1 F in Depression.

Depression is a common, severe, and debilitating psychiatric disorder of unclear etiology. Our previous study has shown that protein phosphatase Mg2+/Mn2+-dependent 1F (PPM1F) in the hippocampal dentate gyrus (DG) displays significant regulatory effects in depression-related behaviors. miR-132-3p plays a potential role in the etiology of depression. This study explored the effect of miR-132-3p on the onset of depression and the possible underlying mechanism for modulating PPM1F expression during the pathology of depression. We found that miR-132-3p levels in the hippocampus of depressed mice subjected to chronic unpredictable stress (CUS) were dramatically reduced, which were correlated with depression-related behaviors. Knockdown of miR-132-3p in hippocampal DG resulted in depression-related phenotypes and increased susceptibility to stress. miR-132-3p overexpression in hippocampal DG alleviated CUS-induced depression-related performance. We then screened out the potential target genes of miR-132-3p, and we found that the expression profiles of sterol regulatory element-binding transcription factor 1 (Srebf1) and forkhead box protein O3a (FOXO3a) were positively correlated with PPM1F under the condition of miR-132-3p knockdown. Finally, as anticipated, we revealed that the activities of Ca2+/calmodulin-dependent protein kinase II (CAMKII) and adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) were reduced, which underlies the target signaling pathway of PPM1F. In conclusion, our study suggests that miR-132-3p was designed to regulate depression-related behaviors by indirectly regulating PPM1F and targeting Srebf1 and FOXO3a, which have been linked to the pathogenesis and treatment of depression.

Spatial Transcriptomics for Tumor Heterogeneity Analysis.

The molecular heterogeneity of cancer is one of the major causes of drug resistance that leads to treatment failure. Thus, better understanding the heterogeneity of cancer will contribute to more precise diagnosis and improved patient outcomes. Although single-cell sequencing has become an important tool for investigating tumor heterogeneity recently, it lacks the spatial information of analyzed cells. In this regard, spatial transcriptomics holds great promise in deciphering the complex heterogeneity of cancer by providing localization-indexed gene expression information. This study reviews the applications of spatial transcriptomics in the study of tumor heterogeneity, discovery of novel spatial-dependent mechanisms, tumor immune microenvironment, and matrix microenvironment, as well as the pathological classification and prognosis of cancer. Finally, future challenges and opportunities for spatial transcriptomics technology's applications in cancer are also discussed.

A proximity labeling method for protein-protein interactions on cell membrane.

Antibodies targeting specific antigens are widely utilized in biological research to investigate protein interactions or to quantify target antigens. Here, we introduce antigen-antibody proximity labeling (AAPL), a novel method to map the antigen interaction sites as well as interactors of antibody-targeted proteins. As a proof of concept, AAPL was demonstrated using sodium/potassium transporting ATPase (ATP1A1) and epidermal growth factor receptor 2 (ERBB2)-specific antibodies that were modified with an Fe(iii) catalytic probe. Once bound to their target proteins, Fe(iii)-induced catalytic oxidation occurred in proximity of the antigen's epitope. Oxidative proteomic analysis was then used to determine the degree of oxidation, the site of oxidation within the targeted antigen, and the interacting proteins that were in close proximity to the targeted antigen. An AAPL score was generated for each protein yielding the specificity of the oxidation and proximity of the interacting protein to the target antigen. As a final demonstration of its utility, the AAPL approach was applied to map the interactors of liver-intestine-cadherin (CDH17) in colon cancer cells.

Novel plasma glycoprotein biomarkers predict progression-free survival in surgically resected clear cell renal cell carcinoma.

INTRODUCTION: Limited data exists on utilization of protein post-translational modifications as biomarkers for clear cell renal cell carcinoma (ccRCC). We employed high-throughput glycoproteomics to evaluate differential expression of glycoprotein-isoforms as novel markers for ccRCC progression-free survival (PFS). METHODS: Plasma samples were obtained from 77 patients treated surgically for ccRCC. Glycoproteomic analyses were carried out after liquid chromatography tandem mass spectrometry. Age-adjusted Cox proportional hazard models were constructed to evaluate PFS. Optimized Harrell's C-index was employed to dichotomize the collective for the construction of Kaplan-Meier curves. RESULTS: The average length of follow-up was 3.4 (range: 0.04-9.83) years. Glycoproteomic analysis identified 39 glycopeptides and 14 non-glycosylated peptides that showed statistically significant (false discovery rate P ≤ 0.05) differential expression associated with PFS. Five of the glycosylated peptides conferred continuous hazard ratio (HR) of > 6 (range 6.3-11.6). These included prothrombin A2G2S glycan motif (HR = 6.47, P = 9.53E-05), immunoglobulin J chain FA2G2S2 motif (HR = 10.69, P = 0.001), clusterin A2G2 motif (HR = 7.38, P = 0.002), complement component C8A A2G2S2 motif (HR = 11.59, P = 0.002), and apolipoprotein M glycopeptide with non-fucosylated and non-sialylated hybrid-type glycan (HR = 6.30, P = 0.003). Kaplan-Meier curves based on dichotomous expression of these five glycopeptides resulted in hazard ratios of 3.9 to 10.7, all with P-value < 0.03. Kaplan-Meyer plot using the multivariable model comprising 3 of the markers yielded HR of 11.96 (P < 0.0001). CONCLUSION: Differential glyco-isoform abundance of plasma proteins may be a useful source of biomarkers for the clinical course and prognosis of ccRCC.

Effect of PPM1F in dorsal raphe 5-HT neurons in regulating methamphetamine-induced conditioned place preference performance in mice.

Methamphetamine (METH), a synthetically produced central nervous system stimulant, is one of the most illicit and addictive drugs worldwide. Protein phosphatase Mg2 + /Mn2 + -dependent 1F F (PPM1F) has been reported to exert multiple biological and cellular functions. Nevertheless, the effects of PPM1F and its neuronal substrates on METH addiction remain unclear. Herein, we first established a METH-induced conditioned place preference (CPP) mouse model. We showed that PPM1F is widely distributed in 5-HT neurons of the dorsal raphe nucleus (DRN), and METH treatment decreased the expression of PPM1F in DRN, which was negatively correlated with METH-induced CPP behaviors. Knockout of PPM1F mediated by adeno-associated virus (AAV) in DRN produced enhanced susceptibility to METH-induced CPP, whereas the overexpression of PPM1F in DRN attenuated METH-induced CPP phenotypes. The expression levels of Tryptophan hydroxylase2 (TPH2) and serotonin transporter (SERT) were down-regulated with a concurrent reduction in 5-hydroxytryptamine (5-HT), tryptophan hydroxylase2 (TPH2)-immunoreactivity neurons and 5-HT levels in DRN of PPM1F knockout mice. In the end, decreased expression levels of PPM1F were found in the blood of METH abusers and METH-taking mice. These results suggest that PPM1F in DRN 5-HT neurons regulates METH-induced CPP behaviors by modulating the key components of the 5-HT neurotransmitter system, which might be an important pathological gene and diagnostic marker for METH-induced addiction.

Cryptotanshinone ameliorates CUS-induced depressive-like behaviors in mice.

OBJECTIVES: Cryptotanshinone (CPT), a natural quinoid diterpene, isolated from Salvia miltiorrhiza, has shown various pharmacological properties. However, its effect on chronic unpredictable stress (CUS)-induced depression phenotypes and the underlying mechanism remain unclear. Therefore, the aim of this study was to investigate whether CPT could exert an antidepressant effect. METHODS: We investigated the effects of CPT in a CUS-induced depression model and explored whether these effects were related to the anti-inflammatory and neurogenesis promoting properties by investigating the expression levels of various signaling molecules at the mRNA and protein levels. RESULTS: Administration of CPT improved depression-like behaviors in CUS-induced mice. CPT administration increased the levels of doublecortin-positive cells and reversed the decrease in the expression levels of brain-derived neurotrophic factor (BDNF)/tyrosine kinase receptor B (TrkB) signaling transduction, as well as the downstream functional proteins, phosphorylated extracellular regulated protein kinases (p-ERK), and cyclic adenosine monophosphate (cAMP)-response element-binding protein levels (p-CREB) in hippocampus. CPT treatment also inhibited the activation of microglia and suppressed M1 microglial polarization, while promoting M2 microglial polarization by monitoring the expression levels of arginase 1 (Arg-1) and inducible nitric oxide synthase (iNOS), and further inhibited the expression of proinflammatory cytokines, including interleukin (IL)-1, IL-6, and tumor necrosis factor-α (TNF-α), and increased the expression of the anti-inflammatory cytokine IL-10 by regulating nuclear factor-κB (NF-κB) activation. CONCLUSIONS: CPT relieves the depressive-like state in CUS-induced mice by enhancing neurogenesis and inhibiting inflammation through the BDNF/TrkB and NF-κB pathways and could therefore serve as a promising candidate for the treatment of depression.

Glycan-protein cross-linking mass spectrometry reveals sialic acid-mediated protein networks on cell surfaces.

A cross-linking method is developed to elucidate glycan-mediated interactions between membrane proteins through sialic acids. The method provides information on previously unknown extensive glycomic interactions on cell membranes. The vast majority of membrane proteins are glycosylated with complicated glycan structures attached to the polypeptide backbone. Glycan-protein interactions are fundamental elements in many cellular events. Although significant advances have been made to identify protein-protein interactions in living cells, only modest advances have been made on glycan-protein interactions. Mechanistic elucidation of glycan-protein interactions has thus far remained elusive. Therefore, we developed a cross-linking mass spectrometry (XL-MS) workflow to directly identify glycan-protein interactions on the cell membrane using liquid chromatography-mass spectrometry (LC-MS). This method involved incorporating azido groups on cell surface glycans through biosynthetic pathways, followed by treatment of cell cultures with a synthesized reagent, N-hydroxysuccinimide (NHS)-cyclooctyne, which allowed the cross-linking of the sialic acid azides on glycans with primary amines on polypeptide backbones. The coupled peptide-glycan-peptide pairs after cross-linking were identified using the latest techniques in glycoproteomic and glycomic analyses and bioinformatics software. With this approach, information on the site of glycosylation, the glycoform, the source protein, and the target protein of the cross-linked pair were obtained. Glycoprotein-protein interactions involving unique glycoforms on the PNT2 cell surface were identified using the optimized and validated method. We built the GPX network of the PNT2 cell line and further investigated the biological roles of different glycan structures within protein complexes. Furthermore, we were able to build glycoprotein-protein complex models for previously unexplored interactions. The method will advance our future understanding of the roles of glycans in protein complexes on the cell surface.

Diet affects glycosylation of serum proteins in women at risk for cardiometabolic disease.

BACKGROUND: Glycoproteomics deals with glycoproteins that are formed by post-translational modification when sugars (like fucose and sialic acid) are attached to protein. Glycosylation of proteins influences function, but whether glycosylation is altered by diet is unknown. OBJECTIVE: To evaluate the effect of consuming a diet based on the Dietary Guidelines for Americans on circulating glycoproteins that have previously been associated with cardiometabolic diseases. DESIGN: Forty-four women, with one or more metabolic syndrome characteristics, completed an 8-week randomized controlled feeding intervention (n = 22) consuming a diet based on the Dietary Guidelines for Americans (DGA 2010); the remaining consumed a 'typical American diet' (TAD, n = 22). Fasting serum samples were obtained at week0 (baseline) and week8 (post-intervention); 17 serum proteins were chosen for targeted analyses. Protein standards and serum samples were analyzed in a UHPLC-MS protocol to determine peptide concentration and their glycan (fucosylation or sialylation) profiles. Data at baseline were used in correlational analyses; change in proteins and glycans following intervention were used in non-parametric analyses. RESULTS: At baseline, women with more metabolic syndrome characteristics had more fucosylation (total di-fucosylated proteins: p = 0.045) compared to women with a lesser number of metabolic syndrome characteristics. Dietary refined grain intake was associated with increased total fucosylation (ρ = - 0.530, p < 0.001) and reduced total sialylation (ρ = 0.311, p = 0.042). After the 8-week intervention, there was higher sialylation following the DGA diet (Total di-sialylated protein p = 0.018, poly-sialylated orosomucoid p = 0.012) compared to the TAD diet. CONCLUSIONS: Based on this study, glycosylation of proteins is likely affected by dietary patterns; higher sialylation was associated with a healthier diet pattern. Altered glycosylation is associated with several diseases, particularly cancer and type 2 diabetes, and this study raises the possibility that diet may influence disease state by altering glycosylation. CLINICAL TRIAL REGISTRATION: NCT02298725 at clinicaltrials.gov; https://clinicaltrials.gov/ct2/show/NCT02298725 .

PPM1F in Dentate Gyrus Modulates Anxiety-Related Behaviors by Regulating BDNF Expression via AKT/JNK/p-H3S10 Pathway.

Anxiety is a serious psychiatric disorder, with a higher incidence rate in women than in men. Protein phosphatase Mg2+/Mn2+-dependent 1F (PPM1F), a serine/threonine phosphatase, has been shown to have multiple biological and cellular functions. However, the effects of PPM1F and its neuronal substrates on anxiety remain largely unclear. In this study, we showed that chronic restraint stress (CRS) induced anxiety-related behaviors only in female mice, while acute restraint stress (ARS) produced anxiety-related behaviors in both male and female mice in light-dark and elevated plus maze tests and induced upregulation of PPM1F and downregulation of brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Adeno-associated virus-mediated overexpression of PPM1F or conditional knockout of BDNF in dentate gyrus (DG) led to a more pronounced anxiety-related behavior in female than in male mice as indicated by the behavioral evaluations. Meanwhile, overexpression of PPM1F in the DG decreased total Bdnf exon-specific messenger RNA expression in the hippocampus with the decreased binding activity of phosphorylated H3S10 to its individual promoters in female mice. Furthermore, we identified that overexpression of PPM1F decreased the phosphorylation levels of AKT and JNK in the hippocampus of female mice. These results may suggest that PPM1F regulates anxiety-related behaviors by modulating BDNF expression and H3S10 phosphorylation-mediated epigenetic modification, which may be served as potentially pathological genes associated with anxiety or other mental diseases.

PPM1F in hippocampal dentate gyrus regulates the depression-related behaviors by modulating neuronal excitability.

Major depressive disorder (MDD) is a common, serious, debilitating mental illness. Protein phosphatase Mg2+/Mn2+-dependent 1F (PPM1F), a serine/threonine phosphatase, has been reported to have multiple biological and cellular functions. However, the effects of PPM1F and its neuronal substrates on depressive behaviors remain largely unknown. Here, we showed that PPM1F is widely distributed in the hippocampus, and chronic unpredictable stress (CUS) can induce increased expression of PPM1F in the hippocampus, which was correlated with depression-associated behaviors. Overexpression of PPM1F mediated by adeno-associated virus (AAV) in the dentate gyrus (DG) produced depression-related behaviors and enhanced susceptibility to subthreshold CUS (SCUS) in both male and female mice, while, knockout of PPM1F in DG produced antidepressant phonotypes under stress conditions. Whole-cell patch-clamp recordings demonstrated that overexpression of PPM1F increased the neuronal excitability of the granule cells in the DG. Consistent with neuronal hyperexcitability, overexpression of PPM1F regulated the expression of certain ion channel genes and induced decreased phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CAMKII) and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) in hippocampus. These results suggest that PPM1F in the DG regulates depression-related behaviors by modulating neuronal excitability, which might be an important pathological gene for depression or other mental diseases.

A site-specific map of the human plasma glycome and its age and gender-associated alterations.

Alterations in the human glycome have been associated with cancer and autoimmunity. Thus, constructing a site-specific map of the human glycome for biomarker research and discovery has been a highly sought-after objective. However, due to analytical barriers, comprehensive site-specific glycoprofiling is difficult to perform. To develop a platform to detect easily quantifiable, site-specific, disease-associated glycan alterations for clinical applications, we have adapted the multiple reaction monitoring mass spectrometry method for use in glycan biomarker research. The adaptations allow for highly precise site-specific glycan monitoring with minimum sample prep. Using this technique, we successfully mapped out the relative abundances of the most common 159 glycopeptides in the plasma of 97 healthy volunteers. This plasma glycome map revealed 796 significant (FDR < 0.05) site-specific inter-protein and intra-protein glycan associations, of which the vast majority were previously unknown. Since age and gender are relevant covariants in biomarker research, these variables were also characterized. 13 glycopeptides were found to be associated with gender and 41 to be associated with age. Using just five age-associated glycopeptides, a highly accurate age prediction model was constructed and validated (r2 = 0.62 ± 0.12). The human plasma site-specific glycan map described herein has utility in applications ranging from glycan biomarker research and discovery to the development of novel glycan-altering interventions.

High Mannose N-Glycans Promote Migration of Bone-Marrow-Derived Mesenchymal Stromal Cells.

For hundreds of indications, mesenchymal stromal cells (MSCs) have not achieved the expected therapeutic efficacy due to an inability of the cells to reach target tissues. We show that inducing high mannose N-glycans either chemically, using the mannosidase I inhibitor Kifunensine, or genetically, using an shRNA to silence the expression of mannosidase I A1 (MAN1A1), strongly increases the motility of MSCs. We show that treatment of MSCs with Kifunensine increases cell migration toward bone fracture sites after percutaneous injection, and toward lungs after intravenous injection. Mechanistically, high mannose N-glycans reduce the contact area of cells with its substrate. Silencing MAN1A1 also makes cells softer, suggesting that an increase of high mannose N-glycoforms may change the physical properties of the cell membrane. To determine if treatment with Kifunensine is feasible for future clinical studies, we used mass spectrometry to analyze the N-glycan profile of MSCs over time and demonstrate that the effect of Kifunensine is both transitory and at the expense of specific N-glycoforms, including fucosylations. Finally, we also investigated the effect of Kifunensine on cell proliferation, differentiation, and the secretion profile of MSCs. Our results support the notion of inducing high mannose N-glycans in MSCs in order to enhance their migration potential.

The Global Phosphorylation Landscape of SARS-CoV-2 Infection.

The causative agent of the coronavirus disease 2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected millions and killed hundreds of thousands of people worldwide, highlighting an urgent need to develop antiviral therapies. Here we present a quantitative mass spectrometry-based phosphoproteomics survey of SARS-CoV-2 infection in Vero E6 cells, revealing dramatic rewiring of phosphorylation on host and viral proteins. SARS-CoV-2 infection promoted casein kinase II (CK2) and p38 MAPK activation, production of diverse cytokines, and shutdown of mitotic kinases, resulting in cell cycle arrest. Infection also stimulated a marked induction of CK2-containing filopodial protrusions possessing budding viral particles. Eighty-seven drugs and compounds were identified by mapping global phosphorylation profiles to dysregulated kinases and pathways. We found pharmacologic inhibition of the p38, CK2, CDK, AXL, and PIKFYVE kinases to possess antiviral efficacy, representing potential COVID-19 therapies.

IGFBP-4 enhances VEGF-induced angiogenesis in a mouse model of myocardial infarction.

Vascular endothelial growth factor (VEGF) is a well-known angiogenic factor, however its ability in promoting therapeutic angiogenesis following myocardial infarction (MI) is limited. Here, we aimed to investigate whether dual treatment with insulin-like growth factor binding protein-4 (IGFBP-4), an agent that protects against early oxidative damage, can be effective in enhancing the therapeutic effect of VEGF following MI. Combined treatment with IGFBP-4 enhanced VEGF-induced angiogenesis and prevented cell damage via enhancing the expression of a key angiogenic factor angiopoietin-1. Dual treatment with the two agents synergistically decreased cardiac fibrosis markers collagen-I and collagen-III following MI. Importantly, while the protective action of IGFBP-4 occurs at an early stage of ischemic injury, the action of VEGF occurs at a later stage, at the onset angiogenesis. Our findings demonstrate that VEGF treatment alone is often not enough to protect against oxidative stress and promote post-ischemic angiogenesis, whereas the combined treatment with IGFBP4 and VEGF can utilize the dual roles of these agents to effectively protect against ischemic and oxidative injury, and promote angiogenesis. These findings provide important insights into the roles of these agents in the clinical setting, and suggest new strategies in the treatment of ischemic heart disease.

Metastasis of cholangiocarcinoma is promoted by extended high-mannose glycans.

Membrane-bound oligosaccharides form the interfacial boundary between the cell and its environment, mediating processes such as adhesion and signaling. These structures can undergo dynamic changes in composition and expression based on cell type, external stimuli, and genetic factors. Glycosylation, therefore, is a promising target of therapeutic interventions for presently incurable forms of advanced cancer. Here, we show that cholangiocarcinoma metastasis is characterized by down-regulation of the Golgi α-mannosidase I coding gene MAN1A1, leading to elevation of extended high-mannose glycans with terminating α-1,2-mannose residues. Subsequent reshaping of the glycome by inhibiting α-mannosidase I resulted in significantly higher migratory and invasive capabilities while masking cell surface mannosylation suppressed metastasis-related phenotypes. Exclusive elucidation of differentially expressed membrane glycoproteins and molecular modeling suggested that extended high-mannose glycosylation at the helical domain of transferrin receptor protein 1 promotes conformational changes that improve noncovalent interaction energies and lead to enhancement of cell migration in metastatic cholangiocarcinoma. The results provide support that α-1,2-mannosylated N-glycans present on cancer cell membrane proteins may serve as therapeutic targets for preventing metastasis.

Determination of the glycoprotein specificity of lectins on cell membranes through oxidative proteomics.

The cell membrane is composed of a network of glycoconjugates including glycoproteins and glycolipids that presents a dense matrix of carbohydrates playing critical roles in many biological processes. Lectin-based technology has been widely used to characterize glycoconjugates in tissues and cell lines. However, their specificity toward their putative glycan ligand and sensitivity in situ have been technologically difficult to study. Additionally, because they recognize primarily glycans, the underlying glycoprotein targets are generally not known. In this study, we employed lectin proximity oxidative labeling (Lectin PROXL) to identify cell surface glycoproteins that contain glycans that are recognized by lectins. Commonly used lectins were modified with a probe to produce hydroxide radicals in the proximity of the labeled lectins. The underlying polypeptides of the glycoproteins recognized by the lectins are oxidized and identified by the standard proteomic workflow. As a result, approximately 70% of identified glycoproteins were oxidized in situ by all the lectin probes, while only 5% of the total proteins were oxidized. The correlation between the glycosites and oxidation sites demonstrated the effectiveness of the lectin probes. The specificity and sensitivity of each lectin were determined using site-specific glycan information obtained through glycomic and glycoproteomic analyses. Notably, the sialic acid-binding lectins and the fucose-binding lectins had higher specificity and sensitivity compared to other lectins, while those that were specific to high mannose glycans have poor sensitivity and specificity. This method offers an unprecedented view of the interactions of lectins with specific glycoproteins as well as protein networks that are mediated by specific glycan types on cell membranes.

Effects of N-Glycosylation on the Structure, Function, and Stability of a Plant-Made Fc-Fusion Anthrax Decoy Protein.

Protein N-glycosylation is an important post-translational modification and has influences on a variety of biological processes at the cellular and molecular level, making glycosylation a major study aspect for glycoprotein-based therapeutics. To achieve a comprehensive understanding on how N-glycosylation impacts protein properties, an Fc-fusion anthrax decoy protein, viz rCMG2-Fc, was expressed in Nicotiana benthamiana plant with three types of N-glycosylation profiles. Three variants were produced by targeting protein to plant apoplast (APO), endoplasmic reticulum (ER) or removing the N-glycosylation site by a point mutation (Agly). Both the APO and ER variants had a complex-type N-glycan (GnGnXF) as their predominant glycans. In addition, ER variant had a higher concentration of mannose-type N-glycans (50%). The decoy protein binds to the protective antigen (PA) of anthrax through its CMG2 domain and inhibits toxin endocytosis. The protein expression, sequence, N-glycosylation profile, binding kinetics to PA, toxin neutralization efficiency, and thermostability were determined experimentally. In parallel, we performed molecular dynamics (MD) simulations of the predominant full-length rCMG2-Fc glycoform for each of the three N-glycosylation profiles to understand the effects of glycosylation at the molecular level. The MAN8 glycoform from the ER variant was additionally simulated to resolve differences between the APO and ER variants. Glycosylation showed strong stabilizing effects on rCMG2-Fc during in planta accumulation, evidenced by the over 2-fold higher expression and less protein degradation observed for glycosylated variants compared to the Agly variant. Protein function was confirmed by toxin neutralization assay (TNA), with effective concentration (EC50) rankings from low to high of 67.6 ng/ml (APO), 83.15 ng/ml (Agly), and 128.9 ng/ml (ER). The binding kinetics between rCMG2-Fc and PA were measured with bio-layer interferometry (BLI), giving sub-nanomolar affinities regardless of protein glycosylation and temperatures (25 and 37°C). The protein thermostability was examined utilizing the PA binding ELISA to provide information on EC50 differences. The fraction of functional ER variant decayed after overnight incubation at 37°C, and no significant change was observed for APO or Agly variants. In MD simulations, the MAN8 glycoform exhibits quantitatively higher distance between the CMG2 and Fc domains, as well as higher hydrophobic solvent accessible surface areas (SASA), indicating a possibly higher aggregation tendency of the ER variant. This study highlights the impacts of N-glycosylation on protein properties and provides insight into the effects of glycosylation on protein molecular dynamics.

Synergistic effect of kaempferol and 5­fluorouracil on the growth of colorectal cancer cells by regulating the PI3K/Akt signaling pathway.

Combination chemotherapy with chemosensitizers can exert synergistic therapeutic effects, reduce toxicity, and delay the induction of drug resistance. In the present study, the antitumor effects were investigated, and the possible underlying mechanisms of kaempferol combined with 5­fluorouracil (5­FU) in colorectal cancer cells were explored. HCT­8 or HCT­116 cells were treated with various concentrations of kaempferol and/or 5­FU for the indicated time­points. An MTT assay was used to determine cell viability, whereas the synergistic effects were assessed by calculating the combination indices of kaempferol and 5­FU. Annexin V analysis and Hoechst staining were used to determine cell apoptosis. q­PCR and western blotting were performed to determine the expression levels of Bax, Bcl­2, thymidylate synthase (TS), PTEN, PI3K, AKT, and p­AKT. The combination of kaempferol and 5­FU was determined to be more effective in inhibiting cell viability than either of the agents alone. The inhibition of tumors in response to kaempferol and 5­FU was associated with the reduction in proliferation ability and stimulation of apoptosis. The protein results indicated that kaempferol and 5­FU could significantly upregulate the expression levels of Bax and downregulate the expression levels of Bcl­2 and TS. Furthermore, the combination treatment greatly inhibited the activation of the PI3K/Akt pathway, suggesting the involvement of this pathway in the synergistic effects. The present study demonstrated that kaempferol has a synergistic effect with 5­FU by inhibiting cell proliferation and inducing apoptosis in colorectal cancer cells via suppression of TS or attenuation of p­Akt activation. The combination of kaempferol and 5­FU may be used as an effective therapeutic strategy for colorectal cancer.

Site-Specific Glycosylation Quantitation of 50 Serum Glycoproteins Enhanced by Predictive Glycopeptidomics for Improved Disease Biomarker Discovery.

Analysis of serum protein glycovariants has the potential to identify new biomarkers of human disease. However, the inability to rapidly quantify glycans in a site-specific fashion remains the major barrier to applying such biomarkers clinically. Advancements in sample preparation and glycopeptide quantification are thus needed to better bridge glycoscience with biomarker discovery research. We present here the successful utilization of several sample preparation techniques, including multienzyme digestion and glycopeptide enrichment, to increase the repertoire of glycopeptides that can be generated from serum glycoproteins. These techniques combined with glycopeptide retention time prediction and UHPLC-QqQ conditions optimization were then used to develop a dynamic multiple-reaction monitoring (dMRM)-based strategy to simultaneously monitor over 100 glycosylation sites across 50 serum glycoproteins. In total, the abundances of over 600 glycopeptides were simultaneously monitored, some of which were identified by utilizing theoretically predicted ion products and presumed m/ z values. The dMRM method was found to have good sensitivity. In the targeted dMRM mode, the limit of quantitation (LOQ) of nine standard glycoproteins reached femtomole levels with dynamic ranges spanning 3-4 orders of magnitude. The dMRM-based strategy also showed high reproducibility with regards to both instrument and sample preparation performance. The high coverage of the serum glycoproteins that can be quantitated to the glycopeptide level makes this method especially suitable for the biomarker discovery from large sample sets. We predict that, in the near future, biomarkers, such as these, will be deployed clinically, especially in the fields of cancer and autoimmunity.