Glycosidase-derived **Gh_112** peptide from gut microbiome mediates selective uptake into cancerous epithelial cells

Intracellular delivery of therapeutics remains a significant hurdle in modern medicine, limiting the efficacy of many promising compounds, including peptides and nucleic acids. Current carrier systems, while useful, often lack the diverse biophysical properties and mechanisms of action needed for a broad range of therapeutic cargo. This creates a critical gap for targeted delivery, especially to specific cell types or tissues. Exploring novel sources for cell-penetrating carriers is essential to overcome these limitations and improve drug bioavailability and specificity. The human gut microbiome, a vast and underexplored reservoir of protein sequences, represents a potential new frontier for discovering such carriers.

Researchers conducted a high-throughput functional metagenomic screen of the human gut microbiome to identify novel cell-penetrating protein fragments. They focused on sequences encoded within glycosidase enzymes from members of the Bacteroidetes phylum. Identified fragments were then displayed on the surface of nonpathogenic, noninvasive Escherichia coli to assess their ability to mediate internalization into human cell lines. One specific fragment, dubbed Gh_112, was selected for further detailed investigation. Its adherence to human fibronectin, activation of endocytic pathways, and selective uptake into various cancerous epithelial cell lines versus healthy tissue were evaluated in vitro.

The high-throughput screen successfully identified multiple protein fragments from the human gut microbiome that exhibited cell-penetrating activity. Specifically, these fragments were encoded within glycosidase enzymes from Bacteroidetes phylum members.

The fragment Gh_112 demonstrated significant and selective internalization into multiple cancerous epithelial cell lines in vitro, while showing minimal uptake into healthy epithelial tissue. Further mechanistic studies revealed that Gh_112 adheres to human fibronectin, a key extracellular matrix protein, suggesting a potential targeting mechanism. The peptide also activated multiple distinct endocytic pathways, indicating a complex and robust internalization process rather than a single entry route. This broad activation of endocytic machinery likely contributes to its efficient cellular uptake. The ability of Gh_112 to promote uptake of E. coli into specific cancerous cells highlights its potential as a targeted delivery vehicle.