Unseen changes at a molecular level hold the key to understanding and treating cardiovascular diseases.
Imagine your body as a sophisticated city, with your heart as its central power station. For this station to run smoothly, countless workers—proteins—must be precisely managed, turned on or off, or sent to specific locations. Post-translational modifications (PTMs) are the master controllers performing this vital management. These subtle chemical changes to proteins after they are built occur in every cell in your body, serving as dynamic regulators that determine how your heart functions, adapts, and sometimes fails.
Proteins are the workhorses of our cells, but they are not static entities. After their initial assembly, most undergo crucial chemical adjustments known as post-translational modifications. These PTMs are fundamental to life, acting as rapid-response systems that allow cells to adapt to changing demands without needing to build new proteins from scratch.
The scale of this process is staggering. While the human genome contains roughly 20,000-25,000 genes, the functional proteome is estimated to encompass over 1 million distinct protein forms, largely due to PTMs . In cardiovascular biology, these molecular switches regulate everything from the heart's pumping force to its energy production and response to damage.
PTMs allow rapid cellular adaptation without new protein synthesis
1M+ protein forms from just 20K-25K genes through PTM combinations
Regulates heart contraction, energy production, and stress response
Several types of PTMs play particularly important roles in cardiovascular health and disease. The table below summarizes the most significant ones:
| Modification Type | Function | Role in Cardiovascular Diseases |
|---|---|---|
| Phosphorylation | Activates/deactivates proteins by adding phosphate groups 1 | Heart failure, ischemia/reperfusion injury, hypertension 2 |
| Acetylation | Regulates gene expression and enzyme activity 2 | Myocardial hypertrophy, heart failure, atherosclerosis 2 6 |
| Ubiquitination | Marks proteins for degradation 1 | Heart failure, cardiac hypertrophy 2 6 |
| SUMOylation | Modifies protein interactions and localization 2 | Cardiac development, hypertrophy, ischemia 2 |
| Glycosylation | Affects protein folding, stability, and cell communication 1 | Heart regeneration, ion channel function 6 |
| Lactylation | Links metabolism to gene expression 1 | Emerging roles in cardiovascular disease 9 |
Protein phosphorylation is perhaps the most studied PTM. It works like a binary switch: the addition of a phosphate group to proteins at serine, threonine, or tyrosine residues can turn their activity on or off . This switch regulates nearly every aspect of cardiac function, from how heart muscles contract to how energy is produced.
The AKT protein, a pivotal kinase, is activated by phosphorylation at two specific sites (Thr308 and Ser473). Once activated, AKT triggers cascades that can either promote or inhibit cardiac hypertrophy—the heart's often harmful response to stress 6 .
Another critical kinase, AMPK, is activated by phosphorylation at Thr172 and plays a key role in the heart's energy management and stress response 6 .
Some PTMs, particularly on histone proteins that package DNA, act as master regulators of gene expression. Acetylation of histones, controlled by the opposing actions of histone acetyltransferases (HATs) and deacetylases (HDACs), can unlock genetic programs that influence heart cell growth and survival 6 . HDAC inhibitors have shown promise in animal studies, reducing myocardial infarct size and preserving cardiac function after ischemia/reperfusion injury 6 .
Methylation provides another layer of control. The histone demethylase JMJD2A promotes cardiac hypertrophy in mice; when JMJD2A is inactivated, hypertrophic responses are significantly blunted 6 . Similarly, the histone methyltransferase G9a is crucial for epigenetic changes during cardiac hypertrophy progression 6 .
Ubiquitination involves attaching a small protein called ubiquitin to target proteins, often marking them for destruction by cellular machinery . This process is vital for removing damaged proteins and regulating key signaling pathways. The E3 ubiquitin ligase Cullin7, for instance, promotes cardiomyocyte proliferation by facilitating the degradation of MST1, thereby activating the growth-promoting YAP pathway 6 .
While we've understood the importance of PTMs for decades, studying them has been challenging because they're often hidden within proteins' complex three-dimensional structures. Traditional methods typically require denaturing proteins—unfolding them from their native state—which can strip away crucial information about how modifications affect protein interactions.
A groundbreaking approach called native top-down mass spectrometry (nTDMS) now allows scientists to study PTMs within intact protein complexes 4 . The experimental workflow follows these essential steps:
Protein complexes are gently isolated from tissues or cells, preserving their native structure and modifications.
Intact protein complexes are introduced into the mass spectrometer, which precisely weighs them.
Complexes are gently disassembled into individual protein subunits.
These subunits are fragmented, and the resulting pieces are analyzed to pinpoint exactly where modifications are located on the protein.
To overcome the challenge of interpreting the incredibly complex data generated, researchers developed an innovative software package called precisION (precise and accurate Identification Of Native proteoforms) 4 . This tool uses a data-driven, fragment-level open search to detect, localize, and quantify previously "hidden" modifications that conventional methods might miss.
The following table outlines essential tools and reagents that enabled this research:
| Research Tool | Function in the Experiment |
|---|---|
| precisION Software | Detects and identifies hidden PTMs from complex spectral data 4 |
| Native Mass Spectrometry | Preserves protein complexes in their near-native state for analysis 4 |
| High-Performance Liquid Chromatography (HPLC) | Separates complex protein mixtures before mass analysis 7 |
| Electron Transfer Dissociation (ETD) | Fragments proteins while preserving labile PTMs for analysis 7 |
When applied to key cardiac proteins, this approach has revealed an unexpected diversity of PTMs. For instance, research on proteins like osteopontin (SPP1)—a signaling factor involved in cardiovascular disease—has uncovered previously undocumented phosphorylation, glycosylation, and lipidation events that were hidden at the intact protein level due to sample complexity 4 .
These findings are crucial because they demonstrate that the PTM landscape of cardiovascular proteins is far more complex than previously appreciated. The ability to detect these modifications while proteins maintain their functional interactions provides unprecedented insights into how multiple PTMs might work together to fine-tune cardiac function.
The growing understanding of PTMs is opening new frontiers in cardiovascular medicine. As research progresses, we're moving toward a future where doctors might:
cardiovascular diseases earlier by detecting specific PTM patterns in blood tests
targeted therapies that correct harmful PTM patterns while preserving beneficial ones
treatments based on an individual's unique PTM profile
The dynamic and reversible nature of most PTMs makes them particularly attractive drug targets. Unlike genetic mutations, which are permanent, PTMs can be chemically modified, offering hope for restoring normal cellular function 5 .
From the initial discovery of phosphorylation to the recent characterization of lactylation and succinylation, our journey to understand the hidden language of protein modifications has fundamentally transformed cardiology. These microscopic switches, though invisible to the naked eye, ultimately determine the macroscopic rhythm of our beating hearts—and hold the key to keeping them healthy for a lifetime.
This article is based on recent scientific research published in peer-reviewed journals including Nature, Cell Death Discovery, FEBS Journal, and Journal of Cardiovascular Translational Research.