In Situ Cellular Glycan Analysis

Abstract

Glycan decorates all mammalian cell surfaces through glycosylation, which is one of the most important post-modifications of proteins. Glycans mediate a wide variety of biological processes, including cell growth and differentiation, cell-cell communication, immune response, pathogen interaction, and intracellular signaling events. Besides, tumor cells aberrantly express distinct sets of glycans, which can indicate different tumor onsets and progression processes. Thus, analysis of cellular glycans may contribute to understanding of glycan-related biological processes and correlation of glycan patterns with disease states for clinical diagnosis and treatment. Although proteomics and glycomics have included great efforts for in vitro study of glycan structures and functions using lysis samples of cells or tissues, they cannot offer real-time qualitative or quantitative information, especially spatial distribution, of glycans on/in intact cells, which is important to the revelation of glycan-related biological events. Moreover, the complex lysis and separation procedures may bring unpredictable loss of glycan information. Focusing on the great urgency for in situ analysis of cellular glycans, our group developed a series of methods for in situ analysis of cellular glycans in the past 10 years. By construction of electrochemical glycan-recognizable probes, glycans on the cell surface can be quantified by direct or competitive electrochemical detection. Using multichannel electrodes or encoded lectin probes, multiple glycans on the cell surface can be dynamically monitored simultaneously. Through design of functional nanoprobes, the cell surface protein-specific glycans and intracellular glycan-related enzymes can be visualized by fluorescence or Raman imaging. Besides, some biological enzymes-based methods have been developed for remodeling or imaging of protein-specific glycans and other types of glycoconjugates, such as gangliosides. Through tracing the changes of glycan expression induced by drugs or gene interference, some glycan-related biological processes have been deduced or proved, demonstrating the reliability and practicability of the developed methods. This Account surveys the key technologies developed in this area, along with the discussion on the shortages of current methodology as well as the possible strategies to overcome those shortages. The future trend in this topic is also discussed. It is expected that this Account can provide a versatile arsenal for chemical and biological researchers to unravel the complex mechanisms involved in glycan-related biological processes and light new beacons in tumor diagnosis and treatment.

Switchable Enzymatic Accessibility for Precision Cell‐Selective Surface Glycan Remodeling

“…For example, hypersialylation is a phenotypic signature displayed by tumor cells to evade immune surveillance . The ability to target a specific type or population of cells for glycan remodeling is therefore essential for the full understanding and precise modulation of glycan functions, tissue‐specific glycan imaging, and tumor immunotherapy . Previous attempts at developing cell‐selective glycan remodeling methods rely on either indirect internal metabolic pathway or direct external enzymatic action .…”

Laser cleavable probes for in situ multiplexed glycan detection by single cell mass spectrometry

“…Traditional technologies limited glycan analysis to the provided data that are averaged over a bulk cell population, [10][11][12][13] but even genetically identical cells present in the same microenvironment can show strong variations in biochemical compositions and even in phenotypes. [14][15][16] The shi from bulk to single-cell analysis is necessary in developing glycan proling, which plays an essential role in measuring cell-to-cell heterogeneity within a population and diagnosing diseases in the early stage.…”

Glycan Nanobiosensors

“…For many years, the role of sugars was considered to be primarily nutritional, but the role of glycans becomes progressively more complex [ 9 ]. Conjugates are part of interfacial layers of cells and responsible for mediation of the first contact in the host-pathogen interactions [ 10 , 11 ]. Highly specific, but weak protein–glycan interactions are commonly observed in nature and have an essential role in many cellular mechanisms, e.g., cell–cell and cell–biomolecule interactions, stabilization of tertiary structure of proteins, mechanism of signaling molecules or disease progression and infection of pathogens including toxins, bacteria and viruses [ 8 , 10 , 11 , 12 , 13 ].…”