Keratin, the protein behind hair and nails, turns out to have a hidden role in controlling skin inflammation

Keratin is the tough, fibrous protein that gives fingernails their hardness, hair its strength, and skin its outermost armor. For most of its scientific history, that structural role was considered the whole story.

But researchers at the University of Michigan have found that one form of the protein has a second, unexpected job. Their study, published in Science Translational Medicine, suggests keratin 16 actively regulates the immune signals that drive inflammation in skin tissue. The discovery grew out of research into a rare, painful genetic disorder — and its implications may reach far beyond it, touching conditions as common as psoriasis and eczema.

A rare disease offered the first clue

Pachyonychia congenita, or PC, is a painful genetic disorder caused by mutations in the KRT16 gene — the gene that encodes keratin 16. In people with PC, those mutations disrupt the dense network of filaments that normally helps skin cells in high-friction zones, particularly the soles of the feet, withstand mechanical stress. Ordinary activities like walking cause skin cells to break down, forming chronic, painful calluses and blisters accompanied by persistent inflammation.

What made PC scientifically interesting beyond its rarity was a pattern researchers noticed in healthy skin. When skin faces stressors — including inflammation — it ramps up production of keratin 16. That raised an obvious but unanswered question: why would a structural protein be produced in greater quantities precisely when the immune system is activated? The answer, it turns out, is that the protein was never purely structural to begin with.

When the brake fails, inflammation surges

To investigate the link between keratin 16 and inflammation, the research team took a multi-pronged approach. They examined thickened skin samples from PC patients, studied lab mice engineered to develop a similar condition, and then created a second group of mice in which the KRT16 gene was disabled entirely.

The results were consistent across every method. When keratin 16 was either mutated or absent, skin inflammation surged — driven by overactive type I interferon signaling. Type I interferons are immune proteins that play a critical role in fighting viruses and cancer, but when their activity goes unchecked, they can trigger excessive, damaging inflammation. In both PC patients and mice lacking functional keratin 16, type I interferon signaling was significantly more active than in healthy controls.

The researchers described keratin 16 as normally acting as a “brake” on the signals skin cells send to recruit the immune system. When that brake fails — through mutation or absence — the immune response accelerates without adequate control.

More than scaffolding: redefining keratin’s role

For most of its scientific history, keratin 16 has been understood primarily as a structural component. Wendy Bollag, a professor of physiology at Augusta University who wasn’t involved in the study, put it plainly: “Keratins are like the steel cables or steel beams of the cell.” That tensile strength is what allows skin to resist breaks and tears that would otherwise let microorganisms in and trigger immune reactions.

The new findings complicate that picture considerably. Study authors Erez Cohen and Pierre Coulombe said that learning about keratin 16’s immune-regulatory function “completely changes how we view the skin’s defense system and the role keratins play within it.” A protein long categorized under structural support now has a documented role in molecular signaling — a meaningful reclassification.

Bollag, assessing the study independently, was struck by its methodological depth. “This article is even more impressive than I thought in terms of all of the different techniques and approaches that were used,” she said. Her core point: when multiple independent methods converge on the same conclusion, the finding carries considerably more weight.

A path toward new treatments

The research team didn’t stop at identifying the mechanism. In a mouse model of PC, they administered an inhibitor of type I interferon signaling and observed clearing of skin lesions. The result is preliminary — based on animal models and tissue samples rather than human clinical trials — but it provides a concrete proof-of-concept.

The broader implications extend well beyond PC. Because type I interferon signaling is implicated in other inflammatory skin conditions, including psoriasis, the findings point toward a potential new therapeutic avenue for diseases that affect far more people. Cohen and Coulombe stated that the work could “identify new ways to treat PC, psoriasis and related conditions.” The researchers also suggested that keratin 16 could serve as both a therapeutic target and a diagnostic marker — a dual role that, if validated, could give clinicians a practical new tool.

What researchers will be watching next

The immediate next step is moving from mice to people. Animal models and patient tissue samples have established the biological plausibility of the keratin 16–interferon connection, but human clinical trials are needed before any new treatment can reach patients. That process is typically lengthy, involving multiple stages of testing for both safety and efficacy.

The conceptual shift this research represents is significant on its own terms. If keratin 16 can be shown to modulate immune signaling in human skin under controlled clinical conditions, it would open a new chapter in how dermatologists approach chronic inflammatory disease. Researchers and clinicians working on psoriasis, eczema, and PC now have a specific molecular pathway to investigate — and, potentially, to target.