PFK Enzyme: New Role in RNA Unwinding & Cell Division Discovered

A long-studied metabolic enzyme, phosphofructokinase (PFK), appears to have a surprising second job: regulating cell division. Research led by the University of Surrey reveals that PFK isn’t just a key player in breaking down sugar for energy – it also directly influences the cell cycle by unwinding RNA and promoting the production of proteins needed for growth. This discovery, published in Nucleic Acids Research, challenges decades of understanding about this fundamental enzyme and could open new avenues for understanding and treating diseases linked to cell cycle misregulation.

Beyond Glycolysis: The Dual Life of Pfk2

For over 70 years, PFK has been recognized as the “gatekeeper” of glycolysis, the process cells use to convert glucose into energy. This ancient metabolic pathway is essential for life and PFK’s role in controlling its speed has been extensively researched. The enzyme exists in yeast, the organism used in this study, as two subunits: Pfk1 (alpha) and Pfk2 (beta). Whereas both subunits were known to perform together in metabolism, the Surrey team’s work demonstrates that Pfk2 possesses a completely separate and previously unknown function.

The researchers found that Pfk2 binds to hundreds of messenger RNA (mRNA) molecules within cells. MRNA carries genetic instructions from DNA to the protein-building machinery of the cell. Pfk2 doesn’t just bind to these mRNA strands; it actively unwinds short, double-stranded sections of RNA in a specific direction. This unwinding action then boosts the translation of genes responsible for driving cell division. Essentially, Pfk2 appears to be signaling to the cell to grow, and divide.

Cell Cycle Disruption Without Pfk2

To understand the impact of this newly discovered function, the researchers examined what happened when Pfk2 was absent in yeast cells. They observed that these cells grew much slower and became significantly larger than normal. More critically, they struggled to progress through the G1 to S phase of the cell cycle. This transition is a crucial checkpoint where cells commit to dividing.

Interestingly, the team found that even without Pfk2’s metabolic function, restoring its RNA-unwinding capability was enough to correct these defects. This was achieved by reintroducing a modified version of Pfk2 that couldn’t perform glycolysis. This result definitively proves that the enzyme’s role in cell division is independent of its traditional metabolic role. This separation of function is a key finding, suggesting a sophisticated level of cellular regulation.

A Molecular Relay Switch: Linking Metabolism to Growth

Professor André Gerber, the corresponding author of the study from the University of Surrey’s School of Biosciences, describes the finding as revealing that PFK functions as a “molecular relay.” He proposes that the enzyme senses the cell’s energy status and uses that information to determine whether to promote growth. “What we have found is that one of its subunits, Pfk2, also functions as an RNA regulator that helps to coordinate when cells divide. What we have is not about energy production,” Gerber explained.

The research team developed a model they call a “molecular relay switch.” When cellular energy levels are low, PFK operates in its typical enzymatic state, prioritizing glycolysis. Still, when energy is plentiful, Pfk2 shifts into a shape that enhances its ability to bind and unwind RNA. This, in turn, promotes the translation of genes involved in the cell cycle, ultimately triggering cell division. This model establishes a direct link between a cell’s metabolic state and its decision to proliferate.

How the Research Was Conducted

The team employed a comprehensive suite of techniques to reach their conclusions. They used RNA sequencing to identify the mRNA molecules that Pfk2 interacts with. Biochemical assays were used to study the molecular behavior of the enzyme, and proteomics – the large-scale analysis of proteins – helped confirm changes in protein levels. They also used a technique called polysome profiling, which separates cell contents to reveal which mRNAs are actively being translated into proteins. This revealed that without Pfk2, mRNAs for key cell cycle regulators, like the G1 cyclin CLN3 and the spindle checkpoint protein BUB3, were less efficiently translated.

Further supporting their findings, the researchers used tests involving light signals to track RNA strands being unwound in real-time. These tests demonstrated that Pfk2, unlike Pfk1, could unwind short double-stranded RNA molecules in a specific direction – a function typically associated with specialized RNA helicase enzymes. This suggests Pfk2 has evolved to take on a role traditionally performed by a different class of proteins.

Implications for Disease and Future Research

Waleed Albihlal, the first author of the study, emphasizes the significance of this discovery. “For decades, PFK has been described in every biochemistry textbook as a unifunctional enzyme acting solely in glycolysis,” he said. “The discovery of this dual function of PFK opens up new avenues to advance our knowledge of critical cell functions.”

The implications of this research extend to a wide range of diseases where cell cycle regulation is disrupted, such as cancer. Understanding how PFK coordinates metabolism and cell division could lead to the development of new therapeutic strategies. The researchers suggest that targeting Pfk2’s RNA-regulating activity could potentially offer a novel approach to controlling cell growth in cancerous tissues. However, it’s significant to note that this research is still in its early stages, and further investigation is needed to determine the feasibility of such therapies.

The study also raises a broader question: how many other enzymes might have hidden functions waiting to be discovered? This finding encourages a re-evaluation of our understanding of enzyme function and suggests that many biological processes may be more interconnected than previously thought. The News-Medical report highlights the potential for future research to uncover similar dual roles in other enzymes.

The next steps involve further investigation into the precise mechanisms by which Pfk2 regulates RNA translation and identifying the specific cellular signals that trigger the switch between its metabolic and RNA-regulating functions. Researchers will also need to explore whether this dual function of PFK is conserved in other organisms, including humans, and whether it plays a role in human diseases. The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Cancer Research UK and the Engineering and Physical Sciences Research Council (EPSRC), indicating a strong foundation for continued exploration.