Imaging cell surface glycosylation in vivo using "double click" chemistry.

Dynamic alterations in cell surface glycosylation occur in numerous biological processes that involve cell-cell communication and cell migration. We report here imaging of cell surface glycosylation in live mice using double click chemistry. Cell surface glycans were metabolically labeled using peracetylated azido-labeled N-acetylgalactosamine and then reacted, in the first click reaction, with either a cyclooctyne, in a Huisgen [3 + 2] cycloaddition, or with a Staudinger phosphine, via Staudinger ligation. The second click reaction was a [4 + 2] inverse electron demand Diels-Alder reaction between a trans-cyclooctene and a tetrazine, where the latter reagent had been fluorescently labeled with a far-red fluorophore. After administration of the fluorescent tetrazine, the bifunctional cyclooctyne-cyclooctene produced significant azido sugar-dependent fluorescence labeling of tumor, kidney, liver, spleen, and small intestine in vivo, where the kidney and tumor could be imaged noninvasively in the live mouse

Metabolic glycan imaging by isonitrile-tetrazine click chemistry.

Seeing the sugar coating: N-Acetyl-glucosamine and mannosamine derivatives tagged with an isonitrile group are metabolically incorporated into cell-surface glycans and can be detected with a fluorescent tetrazine. This bioorthogonal isonitrile-tetrazine ligation is also orthogonal to the commonly used azide-cyclooctyne ligation, and so will allow simultaneous detection of the incorporation of two different sugars

Glycosylation in Indolent, Significant and Aggressive Prostate Cancer by Automated High-Throughput N-Glycan Profiling

The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies

Sialylation of N-Linked Glycans Influences the Immunomodulatory Effects of IgM on T Cells

Abstract Human serum IgM Abs are composed of heavily glycosylated polymers with five glycosylation sites on the μ (heavy) chain and one glycosylation site on the J chain. In contrast to IgG glycans, which are vital for a number of biological functions, virtually nothing is known about structure–function relationships of IgM glycans. Natural IgM is the earliest Ig produced and recognizes multiple Ags with low affinity, whereas immune IgM is induced by Ag exposure and is characterized by a higher Ag specificity. Natural anti-lymphocyte IgM is present in the serum of healthy individuals and increases in inflammatory conditions. It is able to inhibit T cell activation, but the underlying molecular mechanism is not understood. In this study, to our knowledge, we show for the first time that sialylated N-linked glycans induce the internalization of IgM by T cells, which in turn causes severe inhibition of T cell responses. The absence of sialic acid residues abolishes these inhibitory activities, showing a key role of sialylated N-glycans in inducing the IgM-mediated immune suppression

Superconducting terminals as sensitive probes for scarred states.

When a quantum-chaotic normal conductor is coupled to a superconductor, the random-matrix theory (RMT) predicts that a gap opens up in the excitation spectrum which is of universal size E_g^RMT approx 0.3 hbar/tD, where tD is the mean scattering time between Andreev reflections. We show that a scarred state of long lifetime tS>>tD suppresses the excitation gap over a window Delta E approx 2E_g^RMT which can be much larger than the narrow resonance width Gamma_S=hbar/tS of the scar in the normal system. The minimal value of the excitation gap within this window is given by Gamma_S/2<<E_g^RMT. Via this suppression of the gap to a nonuniversal value, the scarred state can be detected over a much larger energy range than it is in the case when the superconducting terminal is replaced by a normal one

N‐glycan signatures identified in tumor interstitial fluid and serum of breast cancer patients: association with tumor biology and clinical outcome

Particular N‐glycan structures are known to be associated with breast malignancies by coordinating various regulatory events within the tumor and corresponding microenvironment, thus implying that N‐glycan patterns may be used for cancer stratification and as predictive or prognostic biomarkers. However, the association between N‐glycans secreted by breast tumor and corresponding clinical relevance remain to be elucidated. We profiled N‐glycans by HILIC UPLC across a discovery dataset composed of tumor interstitial fluids (TIF, n = 85), paired normal interstitial fluids (NIF, n = 54) and serum samples (n = 28) followed by independent evaluation, with the ultimate goal of identifying tumor‐related N‐glycan patterns in blood of patients with breast cancer. The segregation of N‐linked oligosaccharides revealed 33 compositions, which exhibited differential abundances between TIF and NIF. TIFs were depleted of bisecting N‐glycans, which are known to play essential roles in tumor suppression. An increased level of simple high mannose N‐glycans in TIF strongly correlated with the presence of tumor infiltrating lymphocytes within tumor. At the same time, a low level of highly complex N‐glycans in TIF inversely correlated with the presence of infiltrating lymphocytes within tumor. Survival analysis showed that patients exhibiting increased TIF abundance of GP24 had better outcomes, whereas low levels of GP10, GP23, GP38, and coreF were associated with poor prognosis. Levels of GP1, GP8, GP9, GP14, GP23, GP28, GP37, GP38, and coreF were significantly correlated between TIF and paired serum samples. Cross‐validation analysis using an independent serum dataset supported the observed correlation between TIF and serum, for five of nine N‐glycan groups: GP8, GP9, GP14, GP23, and coreF. Collectively, our results imply that profiling of N‐glycans from proximal breast tumor fluids is a promising strategy for determining tumor‐derived glyco‐signature(s) in the blood. N‐glycans structures validated in our study may serve as novel biomarkers to improve the diagnostic and prognostic stratification of patients with breast cancer