The team, led by senior author Daniel G. Isom, Ph.D., a Sylvester researcher and faculty member in the Department of Molecular and Cellular Pharmacology, turned to a vast computational dataset containing more than 214 million predicted protein structures. Rather than scanning for familiar sequence signatures, the researchers asked a different question: which of these predicted proteins fold into shapes that resemble known functional families, even if their sequences look like nothing recognizable? Their search concentrated on the G protein-coupled receptor family, or GPCRs, an enormous group of membrane proteins that allow cells to sense and respond to signals arriving from outside the cell. GPCRs are among the most heavily exploited targets in pharmacology, so any undiscovered relatives are of more than academic interest.

“For decades, we have largely explored protein biology using sequence as our guide,” Isom said. “We wanted to know what biology we might be missing if we searched by three-dimensional structure instead. What we found suggests there is another layer of biology that has been hiding in plain sight.” The structural approach flagged a set of proteins that classical sequence-based methods had never connected to the GPCR family, a category sometimes described as part of the dark proteome, the substantial fraction of predicted proteins whose functions remain entirely unknown.

One protein in particular stood out. Known as TM184C, it folded like a GPCR, but when the team examined its behavior in cells, it refused to follow the expected script. Classic GPCRs typically sit in the plasma membrane at the cell’s surface, waiting for extracellular ligands. TM184C, by contrast, was found largely inside the cell, embedded in the membranes of intracellular vesicles, the tiny membrane-bound packages that cells use to ferry materials between compartments and to one another. That difference in localization alone hinted that TM184C might represent an entirely new mode of GPCR-like function.

Following the protein’s location in living cells revealed something stranger still. The TM184C-positive vesicles did not sit still. They traveled along microtubules, the rigid protein filaments that serve as the cell’s internal highway system, and they accumulated in thin projections that extend from one cell toward its neighbors. These projections acted like bridges. Through them, the researchers observed cells exchanging metabolites, vesicles, and even entire organelles, including mitochondria, the power-generating structures that supply the energy currency of life. The discovery suggests that direct, physically connected exchange between neighboring cells may be far more common, and far more consequential, than previously appreciated.

“When we saw TM184C-positive vesicles moving through connections between cells, we realized these structures could be routes for substantial material exchange,” said Jenniffer Arcuri, Ph.D., a senior scientist with Sylvester and the study’s lead author. “That completely changed how we thought about TM184C and made us consider how cells might use these connections to cooperate and compete for resources.” To test whether the protein actually mattered, the team disrupted TM184C in cultured cells. The effect was clear: the cells formed fewer intercellular connections, and their overall shape and vesicle organization changed, indicating that TM184C helps build and manage these intercellular conduits rather than merely riding along inside them.

The findings raise a question that cuts to the heart of tissue biology: when neighboring cells share resources, who benefits? In healthy tissue, the exchange could be a form of cooperation, allowing cells under stress to survive by shuttling fuel, building blocks or damaged components to wherever they are needed most. But the conduits could also be exploited. If the exchange is unequal, one cell might gain at another’s expense, drawing support from a weaker neighbor. That possibility becomes especially provocative in cancer, where tumor cells frequently endure low oxygen and scarce nutrients. Intercellular bridges could give some cancer cells a lifeline, allowing them to share resources or siphon support from surrounding tissue in ways that conventional metabolic studies, which typically analyze cells in isolation, would never detect.

“I think cells coordinate until they have to compete,” said Shraddha Chandthakuri, a Cancer Biology doctoral student in the Isom lab. “When the cells are stressed, they may coordinate to redistribute the proteins, organelles, and metabolites to support the survival of the population as a whole.” Bruno Colon, a Molecular and Cellular Pharmacology graduate student in the same lab, is now probing that dynamic directly. “What excites me most is understanding what this exchange actually does to the cells on both sides,” Colon said. “As part of my doctoral work in the Isom lab, I am studying how these connections occur in normal cells and aggressive cancers like glioblastoma. Understanding their role could give us new insight into how these tumors communicate and potentially reveal vulnerabilities we haven’t recognized before.”

TM184C appears to influence more than just physical connectivity. The protein also seems to help regulate autophagy, the recycling program by which cells break down and reuse old or damaged components, a process critical to surviving starvation and other stresses. In the study, when the researchers reduced the amount of TM184C in cells, markers of autophagy rose, suggesting the protein normally acts as a brake or tuning mechanism on the process. Adding a structural dimension to the evidence, the team studied a yeast protein called Hfl1 that resembles the human protein. When Hfl1 was removed from yeast, the cells developed noticeable defects. Remarkably, inserting human TM184C into those yeast rescued the problems, demonstrating that the protein’s essential function has been conserved across roughly a billion years of evolution separating baker’s yeast from humans.

For Isom, the broader lesson is about method as much as mechanism. He emphasized that the work depended on pairing AI-driven structure prediction with rigorous experimental validation, not on trusting the algorithms alone. “AI cannot be blindly trusted, but can lead to really big things in the hands of experts and prepared minds,” he said. “For decades, biomedical research has understandably concentrated on the proteins we could identify and understand. But there is another layer of biology that has remained largely invisible to us. AI gives us a way to start exploring it systematically. TM184C is one example of what can be found when we look.” The implication is that artificial intelligence is not merely accelerating the pace of existing science; it is changing what scientists can see at all. TM184C, pulled out of the dark proteome by searching the shapes rather than the sequences of 214 million predicted proteins, offers both a new way to study how cells communicate, survive stress and possibly drive disease, and a template for finding whatever else has been hiding in plain sight.

Subject of Research: Discovery and functional characterization of the hidden GPCR-like human protein TM184C, which regulates intercellular exchange and autophagy

Article Title: AI helps find hidden human proteins and reveals what they do

Article References: AI helps find hidden human proteins and reveals what they do. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: TM184C, GPCR, dark proteome, artificial intelligence, protein structure prediction, intercellular exchange, autophagy, vesicles, mitochondria, cell-to-cell bridges, Sylvester Comprehensive Cancer Center, cancer biology

G protein-coupled receptors, or GPCRs, form the largest receptor family in most animal genomes and are the targets of a substantial fraction of modern medicines. Classically, these proteins thread through the membrane seven times, forming a bundle that shifts shape when a hormone, neurotransmitter, or sensory molecule binds on the outside, thereby activating G proteins and other signaling partners on the inside. TM184C shares the hallmark seven-transmembrane architecture of this family, but the new work argues that its role is not the canonical one. Instead of simply relaying external signals, the protein appears to sit at the interface of membrane trafficking systems that determine what can pass between neighboring cells and what gets delivered to the lysosome for degradation. That dual assignment, intercellular exchange on one hand and autophagy on the other, points to a coordinating function at a junction where membrane biology has long been studied but poorly unified.

Intercellular exchange is a broad term covering several distinct mechanisms by which one cell transfers material to another. Cells can release small membrane-enclosed vesicles such as exosomes, form transient cytoplasmic bridges, or engage in contact-dependent transfer at specialized junctions. These processes matter in immunity, where antigen fragments are handed between immune cells; in development, where signaling molecules and even organelles can move between neighboring cells; and in disease, where tumor cells exploit exchange pathways to spread survival signals or drug resistance. The identification of TM184C as a regulator of such exchange suggests that at least part of this traffic is actively managed by a dedicated protein rather than arising purely from generic membrane dynamics. Understanding which exchange route TM184C controls, and how its GPCR-like fold supports that control, is now a central question raised by the study.

Autophagy, the second process attributed to TM184C, is the cell’s quality-control and recycling program. Through a sequence of carefully choreographed steps, the cell wraps damaged organelles, protein aggregates, and invading microbes in a double-membrane vesicle called an autophagosome, which then fuses with lysosomes where the contents are broken down into building blocks the cell can reuse. Autophagy is induced by starvation and stress, but a basal level runs continuously, clearing molecular wear and tear. Defects in the pathway are implicated in neurodegenerative disease, cancer, and metabolic disorders, which is why the machinery of autophagy has been mapped in extraordinary detail over the past three decades. That a GPCR-like protein would feed into this system is notable because autophagy regulation has traditionally been dominated by a different cast of characters: kinase cascades, ubiquitin-like conjugation systems, and adaptor proteins that recognize cargo.

The conceptual bridge between the two roles may lie in membrane handling. Both intercellular exchange and autophagy depend on the cell’s ability to remodel, tether, and fuse membranes with precision. Vesicles that leave one cell to enter another must bud, travel, and merge with target membranes; autophagosomes must nucleate from a specific membrane source, engulf cargo, and fuse with lysosomes. A protein with seven membrane-spanning segments has the structural means to sit within such membranes and influence their curvature, composition, or interactions with the trafficking machinery. The authors’ designation of TM184C as GPCR-like rather than simply a GPCR is therefore meaningful: it implies conservation of the fold, and possibly of some regulatory logic, without necessarily implying ligand binding and classical signal transduction. Evolutionary biologists have increasingly recognized that receptor-like folds are sometimes repurposed for transport, adhesion, or scaffolding roles, and TM184C may be a fresh example of that repurposing.

For researchers in membrane biology, the study offers a potential new handle on a long-standing puzzle: how cells coordinate what they send out with what they break down. If the same molecular apparatus governs both export routes and lysosomal delivery, then signals that alter TM184C function could simultaneously change how a cell communicates with its neighbors and how it recycles its own components. Such coupling would have wide implications. In the immune system, for instance, the presentation of antigens to other cells depends on both vesicular transfer and autophagic processing of intracellular proteins. In cancer, tumor cells often boost both exosome secretion and autophagy to survive hostile conditions, and a single regulator touching both pathways would be an attractive target for therapeutic intervention. The study’s framing of TM184C as a point of convergence makes these connections explicit even as many mechanistic details remain to be worked out.

The technical path to such a discovery typically involves a combination of genetic, cell biological, and structural approaches. Identifying a protein as a regulator of intercellular exchange generally requires assays that measure transfer of fluorescent or functional cargo between cells, coupled with perturbations, such as gene knockout or knockdown, that reveal what changes when the protein is absent. Assigning a role in autophagy demands complementary readouts: accumulation of autophagosome markers, flux assays that distinguish blocked degradation from increased autophagosome formation, and electron microscopy or biochemical fractionation to see where the protein acts in the pathway. Demonstrating GPCR-like character involves sequence and structural analysis confirming the seven-transmembrane arrangement and comparison with known receptor families. While the published report’s full experimental detail is not reproduced here, the combination of claims in the title indicates that the authors crossed these methodological thresholds, positioning TM184C within both the exchange and autophagy literatures simultaneously.

What makes the result likely to draw broad attention is the sheer prominence of both processes in current biology. Autophagy research has been recognized with a Nobel Prize, and extracellular vesicles have become one of the fastest-growing areas of biomedical science, driven by their roles in intercellular communication and their potential as drug delivery vehicles. A molecule that links these two fields creates an immediate agenda: structural biologists will want to see the protein’s architecture at atomic resolution; cell biologists will want to map its interaction partners and pinpoint which trafficking step it controls; physiologists will want to know in which tissues it matters most; and clinicians will ask whether its dysfunction contributes to diseases where exchange or recycling goes wrong. Each of these questions is standard follow-up for a new regulator, but few new regulators arrive with credentials in two such active areas at once.

There are also evolutionary implications worth noting. GPCR-like proteins that do not signal in the classical sense have been described before, including adhesion GPCRs with long N-terminal domains that function partly as structural tethers, and various orphan receptors whose ligands remain unknown. TM184C extends this spectrum by suggesting that the receptor fold can be recruited for intracellular membrane management, not just surface sensing. If homologs of TM184C exist across species, comparative studies could reveal when this exchange-and-autophagy function arose and how conserved it is, from single-celled organisms to complex animals. Conversely, if the protein is restricted to particular lineages, that distribution could explain why it escaped attention for so long and hint at specialized biological contexts, perhaps in tissues with high exchange demands, where its function is most critical.

As with any first report of a new regulator, caution is warranted until independent laboratories reproduce the findings and extend them. The field will want clarity on whether TM184C binds any ligand, whether it couples to G proteins at all, and exactly which step of autophagy it influences, from initiation to cargo recognition to lysosomal fusion. It will also matter whether the intercellular exchange phenotype reflects a direct role in vesicle formation or an indirect consequence of altered membrane homeostasis. Nevertheless, the study establishes a clear identity for TM184C and a defined set of processes to interrogate. In a research landscape where the boundaries between signaling, trafficking, and degradation are increasingly seen as porous, a GPCR-like protein that regulates both intercellular exchange and autophagy is a fitting emblem of that shift, and a reminder that some of the cell’s most important traffic controllers may have been hiding in plain sight within the receptor family’s structural vocabulary.

Subject of Research: TM184C, a GPCR-like regulator of intercellular exchange and autophagy

Article Title: TM184C is a GPCR-like regulator of intercellular exchange and autophagy

Article References: Lee, K. D., Taylor, S., Arcuri, J., Chandthakuri, S., Pujols, J., Colon, B., Wang, Q., Wu, C., Meng, Z., Thompson-Ceccato, S. J., Mitchell, J., Bayik, D., Carbone, A., Slepak, V., Slepak, T. I., Welford, S. M., Ivan, M. E., Wang, D., Goldberg, B. O., … Isom, D. G. (2026). TM184C is a GPCR-like regulator of intercellular exchange and autophagy. Nature. https://doi.org/10.1038/s41586-026-10993-8

Image Credits: AI Generated

DOI: 10.1038/s41586-026-10993-8

Keywords: TM184C, GPCR-like protein, autophagy, intercellular exchange, membrane trafficking, cell biology, exosomes, lysosomes, seven-transmembrane protein, cellular recycling, vesicle transfer, Nature