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Quantification and Size-profiling of Extracellular Vesicles Using Tunable Resistive Pulse Sensing
Published on: October 19, 2014
Nano-sized CA125 antigen glycocamouflage: Mucin - Extracellular vesicles alliance to watch?
Ninoslav Mitić1, Maja Kosanović1, Bojana Milutinović1
1Department of Immunochemistry and Glycobiology, Institute for the Application of Nuclear Energy, INEP, University of Belgrade, Banatska 31b, 11080, Belgrade, Serbia.
Abstract:
Mucin 16 (MUC16) is a transmembrane type mucin and its released extracellular portion is designated as CA125 antigen. It is considered to be part of a supramolecular glycoprotein complex having a complicated epitope map and extreme structural heterogeneity. Starting from the initial transmembrane localization of MUC16/CA125 antigen and its alternative routes of release by shedding or putative secretion, CA125 antigen from human amniotic fluid soluble and extracellular vesicles (EVs)-containing fractions were characterized aiming at the possible glycosylation-associated mode of distribution as a factor contributing to the reported conflicting structural data. Ultracentrifugation, sucrose density gradient centrifugation, ion-exchange chromatography and TEM were used for analysis. The results indicated that the smeared abundantly glycosylated high molecular mass CA125-immunoreactive species, which follow the wheat germ agglutinin-binding pattern, were shared across amniotic fluid soluble and particulate fractions. A lower molecular mass glycoprotein-like CA125-immunoreactive species which follows the peanut agglutinin-binding pattern and was specifically associated with the EVs-enriched fraction was observed. CA125 presentation in the particulate amniotic fluid fraction was found to be shaped by a complex interactome partially involving lactose-sensitive galectin-3 binding. The MUC16 - EVs alliance as well as heterogeneous mucin/macromolecular complexes, at membranes or extracellularly, may represent cryptic pools of distinct CA125 species.
Insights
Mucin 16 (MUC16), known as CA125 antigen, exhibits varied structures in amniotic fluid. This study reveals distinct glycosylation patterns in soluble and extracellular vesicle (EV)-associated CA125, explaining structural heterogeneity.
Area of Science:
- Biochemistry
- Glycobiology
- Cell Biology
Background:
- Mucin 16 (MUC16) is a transmembrane mucin, with its extracellular portion identified as CA125 antigen.
- CA125 exhibits significant structural heterogeneity and a complex epitope map, leading to conflicting data.
- Understanding MUC16/CA125 release mechanisms and distribution is crucial for interpreting its biological roles.
Purpose of the Study:
- To characterize CA125 antigen in human amniotic fluid, focusing on soluble and extracellular vesicle (EV)-containing fractions.
- To investigate the role of glycosylation in the distribution and structural heterogeneity of CA125.
- To explore potential interactions shaping CA125 presentation in different biological compartments.
Main Methods:
- Ultracentrifugation and sucrose density gradient centrifugation for fractionation.
- Ion-exchange chromatography and Transmission Electron Microscopy (TEM) for analysis.
- Lectins (WGA, PNA) and galectin-3 binding assays to assess glycosylation and interactions.
Main Results:
- Abundantly glycosylated, high molecular mass CA125 species with WGA-binding patterns were found in both soluble and particulate amniotic fluid fractions.
- A distinct lower molecular mass, PNA-binding CA125 species was specifically associated with EV-enriched fractions.
- CA125 in particulate fractions showed complex interactions, including lactose-sensitive galectin-3 binding.
Conclusions:
- CA125 antigen exists in diverse forms within amniotic fluid, influenced by glycosylation.
- The association of MUC16 with EVs contributes to CA125 heterogeneity.
- Heterogeneous mucin complexes, both membrane-bound and extracellular, represent distinct pools of CA125 species.
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