Li 2019 — 4PBA in Cdh23 Mice (Neuroreport)
Journal: Neuroreport, December 2019
PMID: 30516593
PMC: PMC6355346
Lab: Qingyin Zheng, Binzhou Medical University + Case Western Reserve University
Key Ideas
- IP 4PBA 50 mg/kg/day starting P7 (preventive design, not rescue) protected ABR thresholds and DPOAE amplitudes in Cdh23^erl/erl mice over 12 weeks versus saline controls.
- Proposed mechanism: CDH23 E1519del mutant protein misfolds in ER, triggers UPR/ER stress. 4PBA as chemical chaperone reduces that ER stress, allowing more correctly folded CDH23 to reach the plasma membrane.
- This is the primary cited paper for “4PBA reaches cochlea at active concentrations.”
Cautionary Framing — Why This Is a Dead End for STRC/Misha
The Li 2019 paper is real data. The cochlear bioactivity is a genuine positive signal. But the mechanism does NOT transfer to STRC:
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CDH23 is an ER-folded transmembrane protein. Its mutant form accumulates in the ER and triggers canonical UPR. That’s what 4PBA’s chemical chaperone activity addresses — it facilitates ER folding checkpoints.
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STRC is an extracellular structural protein secreted from the cell. It doesn’t accumulate in the ER. E1659A may destabilize folding in transit, but the protein isn’t ER-trapped — it just doesn’t assemble correctly into horizontal top connectors once secreted. 4PBA’s ER-stress mechanism has no functional target in STRC biology.
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Study quality is weak. n=6 per group, no power analysis reported, no absolute dB threshold values stated in the paper text. Zero replications in the 6+ years since publication. A 2024 Frontiers ER stress review covering this exact disease area doesn’t cite it. The design is preventive (P7 start before hearing onset), not rescue — irrelevant to a 4-year-old child who already has hearing loss.
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Mechanism mismatch is the killer. Even if 4PBA reaches cochlear fluid at therapeutic concentrations, it can’t rescue an extracellular structural protein that isn’t ER-trapped. The mechanistic logic doesn’t chain.
What This Paper Does vs Doesn’t Prove
| Question | Li 2019 answer |
|---|---|
| Does 4PBA reach the cochlea at active concentrations? | Probably yes — indirect evidence from ABR/DPOAE in Cdh23 mice |
| Does 4PBA rescue CDH23 misfolding? | Yes, in Cdh23^erl mice via ER stress reduction |
| Does 4PBA rescue STRC E1659A? | No evidence; mechanism doesn’t apply |
| Is Li 2019 a strong paper? | No — n=6, no power analysis, undetailed reporting, 0 replications in 6+ years |
Connections
[contradicts]STRC Repurposed FDA Chaperone Branch — mechanism mismatch kills 4PBA as STRC-specific therapeutic; this paper was the evidence base that looked promising but doesn’t transfer[see-also]STRC Pharmacochaperone Virtual Screen E1659A[about]Misha