Blocking NEDD4L-Mediated ACE2 Ubiquitination at Lysine 788 Alleviates Hypoxia- Induced Pulmonary Hypertension: A Mechanistic Study
This study demonstrates that blocking NEDD4L-mediated ubiquitination of ACE2 at the specific lysine 788 residue prevents its degradation, thereby stabilizing ACE2 levels and alleviating hypoxia-induced pulmonary hypertension in rats, suggesting a precision therapeutic strategy that targets this interaction without inhibiting global NEDD4L function.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
The lungs are a delicate balance of pressure and flow, a system where blood vessels must remain open and flexible to deliver oxygen to the body. When this system fails, a condition known as pulmonary hypertension can develop, causing the vessels to stiffen and narrow. This forces the heart to work harder against increasing resistance, eventually leading to heart failure. One of the key players in keeping these vessels healthy is a protein called ACE2, which acts as a protective regulator, helping to relax blood vessels and prevent them from thickening. However, in diseased lungs, the body often loses this protection because the ACE2 protein is broken down too quickly. The mechanism behind this breakdown involves a cellular recycling system that tags proteins for destruction, but until now, scientists did not know exactly which part of the ACE2 protein was being targeted or how to stop it without disrupting other essential body functions.
A team of researchers at Xuzhou Medical University has now pinpointed the exact spot where this destruction begins and demonstrated that blocking it can restore health to the lungs. They focused on a specific amino acid, a tiny building block within the ACE2 protein, located at position 788. In healthy cells, a molecular machine known as NEDD4L attaches a tag to this specific spot, signaling the cell to discard the ACE2 protein. The researchers hypothesized that if they could prevent the tag from attaching to this single location, the protective protein would survive longer and keep the blood vessels open. To test this, they created a modified version of the ACE2 protein where the vulnerable spot at position 788 was swapped for a different building block that the tagging machine could not recognize. This change was designed to be subtle, altering only the target site while leaving the rest of the protein's structure and function intact.
The team first tested this idea in cells taken from the blood vessels of the lungs. They introduced the modified protein and observed that the tagging machine could no longer grab onto it, confirming that position 788 was indeed the critical handle used for destruction. When they looked at how these cells behaved, they found that the normal version of the protein helped stop the cells from dividing too rapidly, a key factor in preventing vessel thickening. The modified protein did this even better, suggesting that keeping the protein stable is crucial for controlling cell growth. Crucially, the cells remained healthy and did not die from the experiment, proving that the modification itself was safe.
To see if this worked in a living organism, the researchers turned to rats that had been genetically engineered to lack the ACE2 protein entirely. Without this protein, these animals are highly susceptible to developing lung disease when exposed to low oxygen levels. The team used a harmless virus to deliver instructions into the rats' lungs, telling them to produce either the original, unmodified ACE2 protein or the new, protected version. They then placed the animals in a chamber with low oxygen for four weeks to simulate the conditions that cause high blood pressure in the lungs. The results were striking. The rats that received the protected version of the protein maintained much lower blood pressure in their lungs compared to those with the original protein. Their blood vessels remained wider and less thickened, and their blood carried oxygen much more efficiently.
Further examination of the lung tissue revealed that the rats with the protected protein suffered far less cell death, a sign that the lung tissue was healthier and more resilient. The researchers also checked the levels of the tagging machine, NEDD4L, and found that while the amount of the machine's instructions increased in the rats with the protected protein, the actual amount of the machine itself dropped in the rats with the original protein. This suggests a complex feedback loop where the cell tries to compensate when the tagging process is blocked, but the end result remains positive for the lung. The study confirms that the protective effect comes from stabilizing the ACE2 protein at the molecular level, rather than simply adding more of it.
This work offers a new perspective on how to treat lung disease by focusing on a single, precise location on a protein rather than trying to shut down an entire cellular system. Because the tagging machine, NEDD4L, is responsible for managing many different proteins in the body, blocking it entirely could cause serious side effects elsewhere. By targeting only the specific spot at position 788 on the ACE2 protein, it may be possible to protect the lungs without disturbing the other vital jobs this machine performs. The researchers acknowledge that while their findings in rats are promising, more work is needed to verify these results in other models and to understand the full scope of how this protection works. Nevertheless, identifying this specific vulnerability provides a clear path forward for developing therapies that could stabilize the lungs' natural defenses against high blood pressure.
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