Introduction
Serum glycoprofiling is a powerful new biomarker-finding technique that shows us how the proteins in our blood are glycosylated. The glycosylated molecules—these molecules—stick to proteins by binding to them by covalently linking them together. Infection, cancer, autoimmune disease, and cardiovascular disease all result in altered serum protein glycosylation profiles. And so serum glycoprofiling has become one of our favorite ways to find novel biomarkers, diagnose disease in the first place, and track disease course or treatment outcome.
In this blog, we’ll see why and how serum glycoprofiling is important, how it works, and how to use it in diagnosis and disease monitoring.
1. What is Serum Glycoprofiling?
Serum glycoprofiling is the total glycan chains of the serum glycoproteins sequenced. The serum is blood’s liquid, and it’s a cumbersome concoction of glycosylated proteins. The enzymes, antibodies, hormones, and acute-phase proteins—that glycoprotein—contribute to just about everything biology does, from immunity to cell signaling to repair.
Glycosylation is an active process, but one also regulated by genes and environmental stressors. It’s a random value for disease states, making it a great biomarker candidate. With serum protein glycoprofiling, pathological glycosylation mutations in disease can be identified as a cause of pathology.
2. Glycosylation and Serum Proteins: Why the FU*K?
Glycosylation is the most common protein post-translational modification. That’s when amino acids are followed by oligosaccharides (glycans) such as asparagine (N-glycosylation) or serine/threonine (O-glycosylation). These glycans can also be extremely differently structured, and this shapes the way the glycoproteins work.
The glycosylation of proteins, antibodies, transferrin, haptoglobin, and the rest is what serum is all about. They operate in the immune system, iron transport, and inflammation, respectively. Glycosylate them in biology, polarity, interactions with other molecules, and that will be disease.
In cancer, for instance, the glycosylation of some proteins changes as the tumor grows. Formally mangled glycans either let the cancer grow (since cancer cells cannot be recognized by the immune system) or multiply. Immunopathological changes in glycosylation might be caused by a supercharged immune system.
So, a more detailed view of glycosylation reactions in serum proteins could be instructive in terms of disease mechanisms and perhaps diagnostic biomarkers.
Serum Glycoprofiling: Taking the Future of Disease Diagnosis and Biomarker Identification Back.
Introduction
The glycosylation of blood proteins is what serum glycoprofiling—one of the best biomarker-discovery tools of our time—reveals. The covalent glucosylation of proteins with carbohydrates is also function-, stability-, and interconnectivity-dependent. Increases in serum protein glycosylation patterns are linked to cancer, autoimmune disorders, and cardiovascular disease. And so serum glycoprofiling is one of the most commonly used approaches to identifying new biomarkers, early disease detection, or an indicator of disease progression or efficacy.
We will be talking about serum glycoprofiling, how to do it, and clinical diagnosis and disease surveillance in this blog.
1. What is Serum Glycoprofiling?
Serum glycoprofiling is an extra-deep examination of the glycans in the serum glycoproteins. As part of the serum (the blood-liquid fraction), the mixture of proteins is modified by glycosylation. These glycoproteins consist of enzymes, antibodies, hormones, and acute-phase proteins—all necessary ingredients of so many biological processes, from immune system activity to cell signaling to wound healing.
Glycosylation is a gene-environment dynamic. It’s dependent on disease, so that’s an excellent one to use in a biomarker search. From glycoprofiles of serum proteins, pathology-specific glycosylation shifts can be recognized as onset markers of pathology.
2. How Does Glycosylation Affect Serum Proteins?
Glycosylation is the most frequent protein post-translational modification. It binds to amino acid oligosaccharides (glycans)—normally asparagine (N-glycosylation) or serine/threonine (O-glycosylation). They can be very different in their architecture, and that will have consequences for how the glycoproteins function.
Especially in serum, proteins such as antibodies, transferrin, and haptoglobin have very specific glycosylation sequences. They serve the immune defense, iron transport, and inflammation, respectively. They can change their glycosylation, and thus biological function, stability, and chemistry with other molecules to produce pathology.
In cancer, for instance, protein glycosylation changes during tumor growth. Changes to glycan structure drive tumors forward by giving cancer cells a way out of immune surveillance or migration. Stable glycosylation also marks abnormal immune systems in autoimmune disorders.
Glycosylation of serum proteins, therefore, might be an invaluable doorway into pathophysiology and an early biomarker for early diagnosis.
3. Methodologies for Serum Glycoprofiling
In the case of full glycoprofiles, there are new de-glycanization, deconvoluting , and measurement of glycans in serum proteins. The most popular are:
3.1. Liquid Chromatography-Mass Spectrometry (LC-MS)
Glycans are quantified with sensitive, accurate， and very sensitive liquid chromatography-mass spectrometry (LC-MS) that is able to perform on very complex samples. The process involves several steps:
Extracting proteins from serum and expulsion of glycans: Proteins from serum are isolated and glycans are expelled by an enzyme such as PNGase F (N-glycans) or O-glycosidases (O-glycans).
Labeling of glycans: Released glycans are occasionally labeled with a fluorescent or mass-tagging agent to identify them quickly in analysis.
Separation chromatographically: Labeled glycans are size-, charge-, or hydrophobicity-separated by HPLC or UPLC (high-performance liquid chromatography).
Mass spectrometry: The broken-up glycans are mass spectrometers known for their structure and content.
It allows us to measure individual glycan molecules and presents us with a whole picture of the glycoprofile in serum.
3.2. Lectin Microarrays
The other serum glycoprofiling method is lectin microarrays. Lectins are proteins that stick directly to carbohydrate chains on glycoproteins. Scientists can look for specific glycan motifs on serum proteins using a microarray with lectins. It is super sensitive and can measure tiny variations in the patterned glycosylation of different glycoproteins in the same solution.
3.3. Enzyme-Linked Lectin Assays (ELLA)
Enzyme-linked lectin assays (ELLA) are like lectin microarrays but in a solid-phase enzyme-linked immunosorbent assay (ELISA). They are particularly useful for the calculation of individual glycans in disease.
3.4. High-Throughput Glycan Profiling
Automation and robotics have now made possible the kind of high-throughput glycan profiling that can be performed on clinical sample sets. Multichannel machines with automated glycan release, labeling, and sequencing allow for fast and adaptable glycoprofiling. These run hundreds of serum samples in parallel; hence, they are best suited for clinical applications and biomarker searches on a large scale.
4. Applications of Serum Glycoprofiling
The applications of serum glycoprofiling in diagnosis, disease surveillance, and biomarker discovery are endless. These are only a few of the more ubiquitous use cases:
4.1. Cancer Diagnosis and Monitoring
Many cancers have glycosylation changes. Truncated or sialylated glycans on tumor glycoproteins, for instance, can be cancer markers. Researchers can look for these variations in glycoprofiling serum samples to develop non-invasive early cancer tests. Glycoprofiling can also be used to track success and relapse with a chronology of glycosylation changes.
4.2. Autoimmune Diseases
Antibiotic-mediated diseases—such as rheumatoid arthritis, lupus, and multiple sclerosis—are accompanied by glycosylation alterations. Alterations in the glycosylation of immunoglobulins (antibodies), for instance, can affect their affinity for antigens or instigate immune reactions.
4.3. Infectious Diseases
The same principle can be used with infectious diseases. Viruses and bacteria normally latch on to host glycoproteins to get to you. Glycosylation of host proteins may be the markers of disease if they are infected. Glycosylation alterations of serum proteins have been reported in HIV and hepatitis infections, for instance, and serum glycoprofiling can be analyzed to track disease activity and therapy response.
4.4. Cardiovascular Diseases
Even acute-phase proteins like haptoglobin and transferrin are reset to glycosylation by inflammation (the biggest culprit in the majority of cardiovascular diseases). Such changes are tracked by serum glycoprofiling and assessed for the risk of atherosclerosis, myocardial infarction, stroke, etc.
4.5. Personalized Medicine
Glycosylation is both gene and environment and with that comes custom medicine. Then, from the individual’s glycoprofile, doctors can identify which disease states the patient is at risk for, what medication might be beneficial, and tailor treatment to the patient.
5. Challenges and Future Directions
Serum glycoprofiling has two things to overcome, though, before the whole clinic is using it. These challenges include:
Glycan Complexity: Glycans are very complex; they are very heterogeneous, and there are so many possible structures that we can’t measure and analyze.
Standardization: There are no standard protocols for glycoprofiling, and the results are not comparable from lab to lab or trial to trial.
Interpretation of Data: Glycoprofiling data isn’t straightforward, as glycosylation differs from gene to gene and disease to environment.
But in time, glycomics, bioinformatics, and high-throughput technologies will cover all of that and bring serum glycoprofiling to the clinic.
Below is a table summarizing some of the services and products offered by Creative Biolabs in the area of glycoprotein development and analysis, along with links to learn more about each one:
These offerings highlight the company’s expertise in custom synthesis and glycoprotein-related research, providing essential tools and services for scientific investigations and product development.