Cells cannot grow indefinitely by simply consuming nutrients. Growth requires a coordinated supply of energy, carbon building blocks and molecular machinery, but it also creates damaged proteins, defective organelles and other waste that must be removed. Autophagy provides one of the cell’s principal quality-control systems. During autophagy, a small membrane structure called a phagophore expands around selected cellular material. The phagophore then closes to form an autophagosome, a double-membraned compartment that delivers its contents to lysosomes for degradation and recycling. This process can supply nutrients during starvation, remove potentially harmful debris and help cells recover from stress. Yet autophagy must be carefully controlled. Too little can allow damage to accumulate, while excessive or mistimed activity can consume essential components. The new findings place PGAM1 at an early decision point in this process, where metabolic status and autophagy initiation can be coordinated rather than regulated as separate cellular programs.

PGAM1 has traditionally been understood as a glycolytic enzyme. In glycolysis, a chain of reactions converts glucose into pyruvate while generating usable energy and producing intermediates that can be diverted into the synthesis of nucleotides, lipids and amino acids. PGAM1 catalyzes the reversible conversion of one phosphorylated sugar intermediate into another, helping maintain the flow of carbon through the pathway. Cancer cells frequently increase glycolytic activity even when oxygen is available, a metabolic pattern associated with rapid biomass production and adaptability. The study shows that PGAM1’s importance extends beyond this catalytic function. When researchers examined complementary yeast and mammalian systems, they found that the protein also acts as a physical organizer for the machinery that initiates autophagy. This distinction is crucial: the same protein can promote growth through its enzyme activity while supporting stress survival through a separate structural role.

The autophagy function of PGAM1 appears to depend on its ability to recruit phosphatidylinositol 3-kinase complex I to the phagophore assembly site. This complex is a central component of the molecular machinery that marks and organizes the membrane where an autophagosome will form. By helping bring the complex to the correct location, PGAM1 effectively licenses the earliest stages of autophagosome biogenesis. Without this recruitment step, the cell may possess the individual ingredients needed for autophagy but fail to assemble them into a functional initiation site. The finding suggests that PGAM1 is not merely associated with autophagy as a downstream consequence of altered metabolism. It operates directly at the point where the autophagic membrane-building program is switched on. In molecular terms, PGAM1 functions as a scaffold: a platform that assembles proteins into a productive complex without necessarily changing those proteins through an enzymatic reaction.

The researchers further found that this role is regulated by phosphorylation mediated by Atg1 in yeast and ULK1 in mammals. These related protein kinases are among the best-known initiators of autophagy, responding to conditions such as nutrient depletion. Phosphorylation changes the behavior of a target protein by adding a phosphate group to specific amino acids, potentially altering its shape, location or binding partners. Under starvation conditions, Atg1 or ULK1-mediated phosphorylation enhances PGAM1’s interaction with Atg14, a component associated with the autophagy-initiation machinery. This provides a direct biochemical route through which stress signals can redirect a glycolytic enzyme toward autophagy control. Rather than treating metabolism and autophagy as independent responses, the mechanism allows a cell to use information about nutrient availability to modify the physical assembly of its recycling apparatus. It also indicates that PGAM1’s checkpoint function is dynamically regulated, becoming especially important when external nutrients are scarce.

Genetic experiments described in the study indicate that PGAM1’s autophagy-regulatory activity is essential and evolutionarily conserved. Conservation across yeast and mammalian systems suggests that the mechanism arose early and has been retained because it solves a fundamental cellular problem: how to maintain growth when nutrients are plentiful and preserve viability when those nutrients disappear. The researchers also found that the autophagy function can be separated genetically from PGAM1’s role in glycolysis. In other words, disrupting the protein’s ability to support autophagy does not simply amount to shutting down its metabolic enzyme activity, and vice versa. This separation strengthens the case that PGAM1 has two distinct molecular identities within the cell. One supports the movement of glucose-derived metabolites through glycolysis; the other helps organize the machinery required to initiate autophagosome formation. Together, the two activities allow cells to match biomass production with quality control and stress tolerance.

That coordination becomes particularly significant in cancer. Tumour cells are under continuous pressure: they must divide rapidly, secure enough nutrients to make new cellular material and survive conditions created by poor blood supply, crowding and fluctuating oxygen or nutrient levels. Increased PGAM1 expression, according to the findings, enhances both glycolytic flux and autophagy capacity. The first effect can provide energy and biosynthetic intermediates for proliferation. The second can help cancer cells recycle internal resources and remove damage when their environment becomes difficult. This combination could give tumour cells a form of metabolic flexibility, allowing them to grow under favorable conditions and endure unfavorable ones. The study reports that disrupting either PGAM1 function markedly impairs tumour growth. That result suggests that cancer cells may depend on the enzyme’s two activities simultaneously, rather than relying only on its established contribution to glycolysis.

The findings could influence how researchers think about targeting metabolic proteins in cancer. A drug designed only to block PGAM1’s catalytic activity might reduce glycolytic output while leaving the protein’s autophagy-scaffolding function intact. Conversely, an intervention that prevents PGAM1 from recruiting autophagy-initiation factors could weaken tumour stress tolerance without necessarily eliminating all glycolytic activity. The study therefore points to a potential therapeutic vulnerability at the interface between metabolism and autophagy. However, the discovery does not by itself establish a treatment or show how such an approach would behave in patients. Autophagy is also essential for normal cells, particularly those exposed to nutrient limitation or other physiological stresses, so broadly suppressing the pathway could carry substantial risks. The significance of the work is instead that it identifies a more precise molecular connection—PGAM1’s interaction with the autophagy machinery—that future research can examine in detail.

More broadly, the study presents cellular survival as a balancing act governed by shared molecular components rather than by isolated pathways. Glycolysis is often described as an energy-producing route, while autophagy is commonly framed as a recycling and quality-control system. PGAM1 shows how those categories can overlap: a protein best known for processing a glycolytic intermediate can also determine whether a membrane structure for autophagy is assembled. Its phosphorylation by Atg1 or ULK1 during starvation places the enzyme within a responsive network that can shift the cell from growth toward maintenance without abandoning metabolism altogether. In cancer, that same integration appears to be exploited, coupling the production of cellular building blocks with the ability to survive stress. By revealing PGAM1 as a metabolic–autophagy checkpoint, the work provides a mechanistic explanation for how cells coordinate proliferation, recycling and resilience—and identifies a molecular junction where the biological logic of healthy adaptation can be repurposed to sustain tumour growth.

Multiple myeloma develops from abnormal plasma cells, the immune cells responsible for producing antibodies. These cancerous cells accumulate in the bone marrow and release large quantities of immunoglobulins, placing exceptional demands on their protein-production machinery. They must continuously fold, transport and maintain vast numbers of proteins while coping with oxidative stress, metabolic pressure and damage to cellular components. Autophagy, a regulated recycling process, helps cells endure these conditions. During autophagy, portions of the cytoplasm, damaged proteins and defective organelles are enclosed in double-membrane structures called autophagosomes. These structures then fuse with lysosomes, where their contents are broken down and recycled.

The new research focuses on ULK3, a member of the Unc-51-like kinase family. Kinases are enzymes that control other proteins by adding phosphate groups to them, thereby changing their activity, location or stability. ULK proteins are widely recognized as early regulators of autophagy, helping cells decide when to initiate the formation of autophagosomes. ULK1 and ULK2 have traditionally received most of the attention in this pathway, while ULK3 has remained less clearly defined. The study now links ULK3 to the biology of multiple myeloma, suggesting that this kinase is not merely a redundant relative of other autophagy regulators but may perform a meaningful function in malignant plasma cells.

The importance of this connection lies in the way myeloma cells use autophagy as a survival strategy. Autophagy is not automatically beneficial or harmful; its effect depends on the cell and its circumstances. In healthy tissues, it can remove damaged mitochondria, eliminate toxic protein aggregates and preserve energy during starvation. In cancer, the same recycling system can help tumor cells tolerate chemotherapy, nutrient deprivation and rapid growth. For plasma-cell cancers, which are burdened by intense protein synthesis, autophagy may be especially valuable because it helps maintain internal quality control and supplies metabolic building blocks when external resources are limited.

According to the study, ULK3 contributes to the ability of multiple myeloma cells to sustain autophagy and remain viable. This finding implies that ULK3 may help coordinate the early steps of the autophagic response or support the broader cellular machinery required to complete it. When such a regulatory node is weakened, cancer cells may lose their capacity to clear damaged material and respond to stress. The result can be an accumulation of defective proteins, impaired organelle function and increased susceptibility to cell death. In myeloma, where the production of abnormal or excessive proteins is already a central feature of the disease, disruption of this balance could be particularly damaging.

The work also offers a biological explanation for why targeting autophagy may affect myeloma survival. Blocking the pathway can produce a form of “stress overload”: cellular waste accumulates, energy production becomes less efficient and damaged components remain in the cytoplasm. At the same time, cancer cells may be unable to reduce their protein burden or adapt to hostile conditions. ULK3 therefore represents a potential control point before the later stages of autophagosome formation and lysosomal degradation. Targeting an early regulator could, in principle, interrupt the process before malignant cells can activate several downstream protective mechanisms.

However, the study does not imply that ULK3 is a universal cancer switch or that a single intervention will eliminate multiple myeloma. Autophagy is a complex network with overlapping regulators, feedback loops and cell-specific effects. If one ULK family member is inhibited, cancer cells may compensate through alternative signaling routes, including pathways controlled by ULK1, ULK2, nutrient-sensing complexes or stress-responsive kinases. The therapeutic challenge will be to determine whether ULK3 can be blocked selectively enough to harm myeloma cells without causing unacceptable injury to normal tissues that also depend on autophagy for long-term maintenance.

The findings are especially relevant to the search for treatments that can overcome drug resistance. Modern myeloma therapy commonly combines agents that attack different aspects of plasma-cell biology, yet many patients eventually relapse because residual malignant cells adapt and survive. A therapy directed at ULK3 could potentially be evaluated alongside established treatments, with the goal of preventing cancer cells from using autophagy as a backup survival program. Such combinations would require careful testing, because some drugs may increase cellular stress and thereby make autophagy inhibition more powerful, while others could trigger compensatory responses that reduce its effect.

Before ULK3 can become a clinical target, researchers will need to clarify how its activity is controlled, which molecular partners it engages and whether its dependence is strongest in particular genetic or metabolic subtypes of myeloma. Biomarkers will also be essential. Measuring ULK3 abundance or activity alone may not predict response if the pathway is governed by several interacting proteins. Investigators may instead need to examine autophagic flux—the rate at which cellular material moves through the pathway—along with protein-folding stress, mitochondrial condition and the molecular features of each patient’s tumor. The study’s central message is therefore both mechanistic and practical: ULK3 helps myeloma cells survive, and understanding that dependence could reveal a new route for weakening a disease that remains difficult to cure.

Subject of Research: Unc-51-like kinase 3 (ULK3), autophagy, cell survival and multiple myeloma

Article Title: Unc-51 like kinase 3 (ULK3) contributes to autophagy and cell survival in multiple myeloma

Article References: Tauro, M., Li, T., Sudalagunta, P.R. et al. “Unc-51 like kinase 3 (ULK3) contributes to autophagy and cell survival in multiple myeloma.” Nature Communications (2026). https://doi.org/10.1038/s41467-026-76711-0

Image Credits: AI Generated

DOI: 10.1038/s41467-026-76711-0

Keywords: ULK3, autophagy, multiple myeloma, plasma cells, cancer cell survival, cellular stress, kinase signaling, therapeutic targets

A breakthrough study conducted by researchers at Aarhus University’s Department of Biomedicine, led by Professor Fulvio Reggiori, has shed light on a critical regulatory mechanism controlling the expansion of this autophagic sack. This discovery centers on a molecular “switch” named Ypt1, also known as RAB1, which orchestrates the enlargement of the phagophore to accommodate varying quantities of cellular debris. Understanding the precise molecular cues that govern this switch opens up exciting avenues for manipulating autophagy therapeutically.

Before this research, the initial formation of the phagophore was relatively well-understood; however, the mechanisms enabling its enlargement remained obscure. The Aarhus team has identified that Ypt1 functions as a gatekeeper, coordinating both the supply of lipid building blocks and the autophagic machinery necessary for phagophore growth. This regulation is essential because the phagophore must adjust its size dynamically depending on the volume of intracellular material targeted for degradation, making Ypt1 a crucial node in cellular homeostasis.

The process begins with the phagophore establishing a physical bridge with the endoplasmic reticulum exit sites (ERES), which are major lipid production factories within the cell. This membrane contact site acts as a conduit through which lipids are delivered to the expanding phagophore membrane. Ypt1 activates this lipid transfer by signaling the formation of this bridge, effectively pressing the “gas pedal” for autophagic expansion. This coordinated response ensures that the autophagic membrane has sufficient resources to encapsulate its cargo fully.

Such a molecular switch not only enhances our fundamental understanding of autophagy but also holds profound implications for human health. In neurodegenerative diseases like dementia and amyotrophic lateral sclerosis (ALS), defective autophagy leads to the accumulation of toxic protein aggregates. By pharmacologically “stepping on the gas,” it might one day be possible to stimulate autophagy and clear these harmful deposits, slowing disease progression. Conversely, many cancer cells exploit autophagy for survival under stressful conditions, suggesting that “hitting the brakes” on Ypt1 activity could starve tumors by disrupting their cellular housekeeping.

The double-edged role of autophagy in health and disease underscores the importance of precise regulation rather than wholesale activation or inhibition. This delicate balance implies that therapeutic modulation must be finely tuned, tailored to the pathological context. The identification of Ypt1’s role in phagophore expansion offers a novel target to develop such therapies, enabling selective augmentation or suppression of autophagic flux as needed.

Professor Reggiori explains that the research utilized advanced biochemical and imaging techniques to decipher these molecular interactions. By mapping the interface between the phagophore and the endoplasmic reticulum, and demonstrating the necessity of Ypt1 for their contact site formation, the study clarifies how cells translate biochemical signals into physical membrane remodeling. This mechanistic insight represents a significant leap forward in the field of cell biology and autophagy research.

Beyond neurodegeneration and cancer, autophagy plays an essential role in immunity and infection control. By modulating autophagic flux, immune cells can enhance the clearance of intracellular pathogens, presenting another therapeutic frontier. Understanding Ypt1’s regulatory function could thus inform drug development aiming to boost host defenses against a range of infectious agents.

While the discovery marks a crucial milestone, the researchers emphasize that more work is needed to translate these findings into clinical applications. The complexity of the autophagy pathway, with its myriad interacting proteins and dynamic membrane behaviors, demands comprehensive study. Future investigations will explore the regulatory networks upstream and downstream of Ypt1, druggable targets within this signaling axis, and potential side effects of modulating this pathway in vivo.

The study also highlights the value of collaborative research, with contributions from experts at Osnabrueck University, Germany, and Cornell University, USA. Supported by funding from the Novo Nordisk Foundation and the Dutch Research Council, this work exemplifies international cooperation in addressing fundamental yet clinically relevant biological questions.

In essence, the identification of Ypt1 as a molecular switch responsible for phagophore expansion provides a crucial missing link in our understanding of autophagy. This foundational knowledge not only enriches basic cell biology but also charts a promising roadmap toward innovative treatments for diseases characterized by cellular waste accumulation or autophagy-dependent survival.

As the field advances, it is conceivable that pharmacological agents targeting the Ypt1 pathway will become part of personalized therapeutic regimens. Such future treatments may revolutionize how conditions like cancer, neurodegeneration, and infections are managed, turning cellular trash management from a mundane housekeeping process into a powerful ally in medicine.

Subject of Research: Molecular regulation of autophagy via the Ypt1/RAB1 switch controlling phagophore expansion

Article Title: Establishment of the phagophore–ERES membrane contact site initiates phagophore elongation

Image Credits: Jens Hartmann Schmidt, Aarhus University

Keywords: Autophagy, phagophore expansion, Ypt1, RAB1, lysosome, membrane contact site, endoplasmic reticulum exit site, neurodegeneration, cancer, intracellular degradation