The promise of TFEB has never been in doubt. The transcription factor controls the expression of hundreds of genes involved in lysosomal biogenesis and autophagy, the twin processes by which cells build new recycling machinery and degrade damaged components. When TFEB is active, it migrates into the nucleus and switches on the genetic program that keeps cellular clearance running. Boosting TFEB activity, researchers reasoned, could help cells cope with the buildup of toxic material that characterizes many diseases. The idea has attracted enormous attention: nearly 3,000 scientific publications now focus on TFEB, more than 90 percent of them appearing in the last decade alone. Experimental studies have explored TFEB activation as a strategy in lysosomal storage disorders, Parkinson’s disease, obesity and cancer, and the protein ranks among the priority targets of the Michael J. Fox Foundation’s Targets to Therapies initiative for Parkinson’s disease.

Yet a stubborn obstacle has kept TFEB from the clinic. Transcription factors as a class are notoriously difficult to target with drugs. They operate inside the nucleus, lack the well-defined enzymatic pockets that medicinal chemists prefer to bind, and are embedded in dense regulatory networks that are hard to manipulate selectively. No therapy specifically designed to activate TFEB has reached patients, despite years of effort. What was missing, essentially, was a handle: an upstream control point that could be pharmacologically tuned to dial TFEB activity up or down. The new study, coordinated by Gennaro Napolitano at TIGEM, provides exactly that. Rather than attacking TFEB itself, the researchers mapped the molecular machinery that senses lysosomal stress and switches TFEB on, revealing several proteins along the way that are far more amenable to drug development.

The scientific lineage of the work runs through Andrea Ballabio, former scientific director of TIGEM, whose research in 2009 first established TFEB as the master regulator of lysosomal function and cellular clearance. That discovery transformed lysosomal biology, recasting the lysosome from a static waste bin into a dynamically regulated system with its own genetic control hub. But one fundamental question remained open: how do cells actually detect that their lysosomes are malfunctioning, and how do they translate that signal into TFEB activation? The sensing step, the molecular bridge between lysosomal perturbation and the nuclear response, had never been fully described. Closing that gap was the central achievement of the new research, which involved collaborators at the University of Fribourg in Switzerland, UC Berkeley in the United States, the University of Rome Tor Vergata in Italy and the German Cancer Research Center (DKFZ) in Germany, with primary support from Fondazione Telethon and Fondazione AIRC.

The answer the team uncovered is a signaling cascade that begins at the lysosome itself. When lysosomal function is disturbed, the lysosomal proton pump known as v-ATPase, a molecular machine that acidifies the organelle’s interior, initiates the response. The stress signal is then transmitted through the adaptor protein TAX1BP1 to two enzymes, TBK1 and ULK1, which become activated. Once switched on, these kinases modify a protein called FNIP1, and this modification sets off a chain of events that releases TFEB to move from the cytoplasm into the nucleus. There, TFEB activates the genes that drive cellular recycling and lysosomal biogenesis. In effect, the cell possesses a dedicated alarm system for lysosomal trouble, wired through TBK1 and ULK1, and TFEB is the responder that answers the call.

“Researchers have known for years that TFEB plays a fundamental role in helping cells maintain their recycling machinery and adapt to stress,” says Alessandra Esposito, first author of the study. “What remained unclear was how cells sense lysosomal dysfunction and translate that signal into TFEB activation. Our work identifies the molecular players involved in this process and reveals a signaling pathway that had never been described before.” The identification of this axis, running from v-ATPase through TAX1BP1 and the TBK1 and ULK1 kinases to FNIP1 and finally TFEB, gives researchers a complete wiring diagram of the lysosomal stress response, and every component in that diagram is a potential point of pharmacological intervention.

The discovery is not only about boosting cellular recycling. The researchers also examined the pathway in the context of follicular lymphoma, a blood cancer in which mutations affecting ATP6V1B2, a component of the v-ATPase proton pump, are relatively common. They showed that these mutations cause persistent activation of TFEB, which in turn helps tumor cells survive and proliferate in nutrient-poor environments, a hallmark of the tumor microenvironment in lymphoma. In this setting, the newly mapped pathway works against the patient: cancer cells exploit the lysosomal stress response to adapt to scarcity and keep growing. That finding suggests a second therapeutic strategy, one of inhibition rather than activation. Drugs that block the TBK1-ULK1 signaling axis might deprive such tumors of their survival advantage, opening a potential avenue for treating follicular lymphoma and possibly other malignancies that depend on lysosomal reprogramming.

“Rather than targeting TFEB itself, our study identifies molecular regulators that control its activation,” Esposito explains. “This provides new entry points for the development of therapeutic strategies aimed at harnessing TFEB activity in disease.” The distinction matters enormously for drug development. Kinases such as TBK1 and ULK1 are enzymes with well-characterized active sites, and potent inhibitors of both already exist in the chemical biology toolkit. A pathway made of kinases and adaptor proteins is, from a medicinal chemistry standpoint, a far more tractable target than a transcription factor. By identifying the regulators upstream of TFEB, the study converts an aspirational goal, pharmacological control of the cell’s recycling master switch, into a concrete set of engineering problems that pharmaceutical researchers know how to approach.

“The identification of the TBK1/ULK1 pathway expands the therapeutic opportunities for modulating TFEB,” says Napolitano, the study’s lead investigator. “Because this mechanism acts upstream of TFEB, it could offer new opportunities not only in TFEB-dependent cancers but also in a broader spectrum of diseases where improving lysosomal function may be beneficial.” That broader spectrum is large. Lysosomal dysfunction lies at the heart of dozens of rare genetic diseases, collectively affecting a substantial number of patients worldwide, and has been implicated in common neurodegenerative disorders, metabolic conditions and aging itself. A single druggable pathway that modulates lysosomal clearance could therefore have applications that span from ultra-rare pediatric storage diseases to some of the most prevalent illnesses of old age.

The study, published under the title describing a TBK1-ULK1 signaling axis that couples lysosomal stress to TFEB activation, marks a turning point in a research story that began in 2009. For fifteen years, the field has known what TFEB does; now it knows how cells control it, and the control points are druggable. Translating that knowledge into medicines will take years of further work, from developing selective modulators of the pathway to testing them in disease models and, eventually, patients. But the direction is clear. By uncovering the molecular sensors and kinases that stand between lysosomal stress and the master regulator of cellular recycling, the TIGEM-led team has brought researchers a decisive step closer to turning one of lysosomal biology’s most celebrated discoveries into real therapies for rare genetic diseases, cancer and beyond.

Subject of Research: The TBK1-ULK1 signaling pathway that regulates TFEB activation in response to lysosomal stress

Article Title: Newly discovered pathway unlocks the therapeutic potential of TFEB

Article References: Newly discovered pathway unlocks the therapeutic potential of TFEB. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: TFEB, lysosomes, TBK1, ULK1, FNIP1, autophagy, lysosomal storage diseases, follicular lymphoma, v-ATPase, TAX1BP1, drug targets, TIGEM