Excess RNA Starves Cells of Energy, New Study Reveals

Research from the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS) indicates that excessive RNA generated during poxvirus infections hinders mitochondria, the cellular components that generate most of the cell's energy.

The study, published in Proceedings of the National Academy of Sciences, highlights a previously unknown link between RNA accumulation and cellular energy generation. These findings might extend beyond viral infections, offering insights into aging-related diseases and advancing RNA-based medical treatments, including mRNA vaccines.

'We've long understood that RNA degradation plays a role in controlling protein synthesis and clearing faulty RNA,' stated Dr. Zhilong Yang, a professor in VMBS' Department of Veterinary Pathobiology. 'Our research unveils an additional vital function: it helps cells maintain the energy necessary for proper functioning.'

Cells continuously produce and break down RNA as part of their regular activity. This process, known as RNA degradation, helps regulate protein production, remove defective RNA, and manage immune responses. The new findings suggest it also protects the cell's energy supply.

Why Too Much RNA Damages Cells

RNA performs various crucial roles in maintaining cell viability. Messenger RNA (mRNA), for instance, carries genetic information directing cells to synthesize proteins. These proteins are fundamental to all cellular processes, from structural integrity to chemical reactions.

Another form, double-stranded RNA (dsRNA), commonly appears during viral infections. Its presence can signal the immune system to a potential viral intrusion.

Viruses produce significant amounts of RNA as they multiply within infected cells. Normally, cellular mechanisms prevent RNA from reaching harmful levels. However, when RNA production surpasses the cell's degradation capacity, the surplus material can disrupt mitochondria and reduce energy output.

It was previously known that excess double-stranded RNA could trigger adverse immune reactions. The researchers were surprised to find that an overabundance of regular messenger RNA could also damage mitochondria.

'mRNA is a natural component of our cells, but like many beneficial elements, an excess can become problematic,' Yang explained. 'When too much RNA accumulates, including mRNA, it can damage mitochondria and impede the cell's energy production.'

This presents a paradox for viruses. While they rely entirely on host cells for energy and protein synthesis, generating excessive viral RNA can damage the very machinery they need to replicate.

According to Yang, poxviruses, which include those causing smallpox and mpox, appear to possess mechanisms for managing this issue. They employ RNA clearance systems to eliminate excess RNA, keeping infected cells functional long enough for viral replication.

'A compromised cell would hinder viral replication,' Yang noted. 'The virus requires balanced RNA levels within the cell.'

Scientists Find RNA Directly Harms Mitochondria

A key unexpected finding emerged when researchers explored how excess RNA impacts mitochondria.

The team initially hypothesized that RNA buildup indirectly damaged these cellular powerhouses by activating the immune system, as certain RNA types are known to provoke defensive responses that stress infected cells.

However, experiments showed damage occurred even without an immune response.

'When we isolated mitochondria and introduced RNA, we still observed mitochondrial damage,' reported Dr. Djamal Brahim Belhaouari, the study's lead author. 'That was the moment we recognized this might be a previously unknown cellular reaction to RNA.'

The researchers also noted that mitochondrial issues arose before significant immune activation. Furthermore, the damage did not involve immune pathways typically activated during infection.

These results suggest that excess RNA itself interferes with mitochondrial function, rather than solely causing damage through the body's response to a virus.

The exact mechanism is still under investigation, but researchers propose a potential explanation involving electrical charges.

Mitochondria generate energy by maintaining an electrical and chemical gradient across their inner membranes. This gradient drives ATP production, the cell's primary energy currency.

RNA carries a negative electrical charge. The researchers suspect that when abnormally high amounts accumulate near mitochondria, they may disrupt the electrical conditions necessary for efficient energy production.

'We believe the negatively charged RNA might gather around mitochondria and disrupt the electrical balance needed for energy production, though the exact process is unknown,' Yang stated. 'This is a novel concept we are continuing to explore.'

Implications for Aging and Disease

While the experiments focused on viral infections, the findings raise questions about RNA accumulation's potential role in other health conditions.

Abnormal RNA buildup has been observed in conditions such as certain cancers, neurodegenerative diseases, and age-related disorders. Neurodegenerative diseases involve the gradual loss of nerve cells, as seen in Alzheimer's and Parkinson's.

Given mitochondria's essential role in cellular health, impaired energy production could contribute to cellular dysfunction in these conditions.

The researchers suggest that excess RNA might be an unrecognized contributor to mitochondrial stress. Further research is necessary to determine the breadth of this mechanism and its direct involvement in these diseases.

'We believe this has significant translational implications,' Belhaouari remarked. 'Excessive double-stranded RNA or mRNA that cannot be effectively degraded may contribute to disease processes in certain contexts.'

Potential Impact on mRNA Vaccines and Future Therapies

The discovery could also inform the development of RNA-based medicines.

RNA therapies, including mRNA vaccines, function by delivering RNA instructions to cells, prompting them to produce specific proteins. Understanding how cells process and degrade RNA is crucial for designing these treatments.

By identifying another way excessive RNA can affect cellular health, these findings may help researchers optimize future RNA-based therapies and vaccines. The study does not conclude that current mRNA vaccines cause mitochondrial damage in humans.

'Understanding this mechanism could aid researchers in designing and refining future RNA-based therapeutics and vaccines by providing a clearer picture of how cells respond to substantial RNA quantities,' Yang commented.

More broadly, the research indicates that RNA level control is vital not only for accurate protein synthesis or immune regulation but also for maintaining mitochondrial function and ensuring sufficient cellular energy.

The most striking outcome for the scientists was realizing that a molecule essential for daily cellular life can become detrimental when its levels exceed normal thresholds.

'Scientists were aware that excessive double-stranded RNA could be harmful,' Yang stated. 'Our surprise came from discovering that too much mRNA—a molecule cells require daily—can also damage mitochondria and disrupt cellular energy production.'