Custom PRPF19 Protein Enables Ferroptosis Drug Target Discovery in Diabetic Nephropathy | AtaGenix

Study Context

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide. While early-stage DN is driven by hemodynamic and metabolic factors, late-stage progression involves a less understood mechanism: ferroptosis — iron-dependent, lipid peroxidation-driven cell death in renal tubular epithelial cells (RTECs). The molecular switch controlling this process remained elusive until this study.

A 2025 study by Qiongyao He and colleagues, published in Cell Communication and Signaling (DOI: 10.1186/s12964-025-02253-5), identified PRPF19 as that switch. Under diabetic conditions, PRPF19 (an E3 ubiquitin ligase) tags the vitamin D receptor (VDR) for proteasomal degradation. Without VDR, the anti-ferroptosis enzyme GPX4 is downregulated, leaving RTECs vulnerable to iron-induced lipid peroxidation. The team then showed that berberine (BBR), a natural alkaloid, directly binds PRPF19 and inhibits its E3 ligase activity — stabilizing VDR and rescuing GPX4 expression. But proving "direct binding" required one critical experiment: SPR with purified PRPF19.

Figure 1. Proposed mechanism: In diabetic conditions, PRPF19 ubiquitinates VDR for degradation, reducing GPX4 and triggering ferroptosis in renal tubular epithelial cells. Berberine (BBR) directly binds PRPF19 to block this cascade, offering a potential therapeutic strategy for diabetic nephropathy.

The Challenge

The entire therapeutic hypothesis rested on one question: does berberine physically bind PRPF19, or does it act through an indirect upstream mechanism? Answering this required SPR — the gold standard for measuring real-time, label-free molecular interactions. But SPR on a Biacore T200 demands protein of exceptional quality: high purity (aggregates produce kinetic artifacts), accurate concentration (for meaningful K_D calculation), and sufficient quantity to run replicate injections across multiple analyte concentrations. The team needed a reliable external partner to deliver this critical reagent.

AtaGenix's Approach

AtaGenix designed the PRPF19 expression and purification workflow specifically for SPR-grade output:

• Expression System: Optimized recombinant expression to produce full-length PRPF19 with intact E3 ligase domain architecture. The system was selected to maximize soluble yield while preserving the protein's native fold.
• Purification for SPR: Multi-step chromatography was tailored to eliminate aggregates and co-purifying contaminants that would compromise Biacore sensorgram quality. Final protein was delivered at 1.67 mg/mL — well above the threshold for amine-coupling chip immobilization and multi-concentration analyte series.
• QC Package: SDS-PAGE confirmed identity and purity. Concentration was verified by Bradford/BCA to ensure accurate SPR data fitting. The protein was additionally validated by the client's own Western Blot and immunoprecipitation assays, confirming functional integrity.

Results and Impact

The AtaGenix-produced PRPF19 enabled the pivotal experiment in the study: Biacore T200 SPR confirmed that berberine directly binds PRPF19 in a concentration-dependent manner, with clear association and dissociation kinetics. This was the key piece of evidence elevating the finding from "berberine reduces PRPF19-mediated VDR degradation" (correlative) to "berberine physically engages PRPF19" (mechanistic).

Figure 2. Biacore T200 SPR analysis. Berberine (BBR) binds to immobilized AtaGenix-produced PRPF19 protein with concentration-dependent kinetics, confirming direct physical interaction. This result established PRPF19 as a bona fide molecular target of berberine in the ferroptosis–diabetic nephropathy axis.

With direct binding established, the study went on to show that berberine treatment stabilized VDR, restored GPX4 expression, and reduced ferroptotic kidney damage in both cell models and diabetic mice — positioning the PRPF19–VDR axis as a promising therapeutic target for DN.

This case study is based on a published research collaboration. Results may vary depending on target protein, construct design, and project scope. All proprietary client information is subject to NDA.