Scientists at the University of Wisconsin-Madison (UW-Madison) have developed a new method, nanoproteomics, which captures and analyzes various forms of the protein cardiac troponin I, or cTnI, more effectively.
Troponin I, or cTnI is a biomarker of heart damage currently used to help diagnose heart attacks and other heart diseases.
According to the study, published in Nature Communications, an effective test of cTnI variations could lead to better ability to diagnose heart disease.
Cardiac troponin I (cTnI)
- Cardiac troponin I (cTnI) is a gold-standard biomarker for cardiovascular diseases.
- cTnI forms the inhibitory subunit of the cTn complex and is released into the bloodstream following cardiac injury where it circulates with low abundance (typically < 50 ng/mL) and in myriad proteoforms (e.g., phosphorylated, acetylated, oxidized, and truncated), making detection and analysis extremely challenging.
- Like many proteins, cTnI can be modified by the body depending on factors like an underlying disease or changes in the environment.
- In the case of cTnI, the body adds various numbers of phosphate groups, small molecular tags that might change the function of cTnI. These variations are subtle and hard to track.
The researchers now plan to use their new method to associate the various forms of cTnI with specific heart diseases as a step toward developing a new diagnostic test.
They found that top-down nanoproteomics can provide high-resolution proteoform-resolved molecular fingerprints of diverse cTnI proteoforms to establish proteoform-pathophysiology relationships.
Carefully designed peptide-functionalized NPs can directly capture and enrich cTnI from human serum with high specificity and reproducibility, while simultaneously depleting highly abundant blood proteins, such as HSA.
These NPs not only outperform conventional monoclonal antibody platforms for serum cTnI enrichment, but also faithfully and holistically preserve all endogenous cTnI proteoforms. Thus, these NPs can serve as replacements to conventional immuno-based techniques to overcome the antibody-related limitations in cTnI immunoassays and potentially address the current reproducibility crisis caused by antibodies in general.
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This antibody-free approach can be leveraged in future clinical cTnI diagnostic assays. By further applying to a large human cohort, patient blood samples can be analyzed to comprehensively detect all cTnI proteoforms and establish the relationships between cTnI proteoforms and underlying disease etiology.
The researchers hope that future blood test will be based on their work which could be complementary to the current ELISA test.
“In the future, when ELISA shows an elevated cTnI level, your doctor might order a comprehensive nanoproteomics test to determine whether it is caused by heart disease or not, and identify different types of heart disease, for more precise treatment while avoiding unnecessary care and expense for patients”, says Song Jin, PhD, professor of chemistry.
UW-Madison Ying Ge, PhD, professor of cell and regenerative biology and chemistry, Song Jin, PhD, professor of chemistry, and chemistry graduate students Timothy Tiambeng and David Roberts led the study.
