STRC GPI-Anchor Analysis
What GPI-Anchor Does
Stereocilin is a GPI-anchored glycoprotein. GPI (glycosylphosphatidylinositol) anchor tethers it to the outer leaflet of the hair cell membrane. Without GPI, protein can’t attach to stereocilia tips or form horizontal top connectors with the tectorial membrane.
GPI Signal in STRC
C-terminal 25 aa: ...GLQDWSRPSWSLVLTISFLGHLL
- Hydrophobic tail:
LVLTISFLGHLL(classic GPI signal) - Omega site candidates: S1758, S1761, S1763
- UniProt Q16563: annotated as GPI-anchored (by similarity)
All mini-STRC constructs preserve the C-terminal intact. The GPI signal is NOT affected by N-terminal truncation.
Web Prediction: NetGPI 1.1 (2026-03-19)
Submitted to NetGPI 1.1 (DTU Health Tech).
Job ID: 69BB8C1F0023C6795E530357 (resubmitted via file upload after first attempt failed with template error)
Three sequences submitted:
- Full STRC (positive control)
- IgK-SP + shorter mini-STRC (our construct)
- Shorter mini-STRC without SP (negative control)
Results: All three constructs predicted GPI-Anchored, omega site S1749 (S in full STRC numbering), likelihood 0.471. Identical across all three. C-terminal GPI signal is not affected by N-terminal truncation.
Plots saved: ~/Sites/site-strc-egor-lol/public/images/netgpi-*.png (404 on DTU server, plots expired)
Prerequisite Chain
For mini-STRC to reach the cell surface:
- Signal peptide → ER entry ✅ (validated by SignalP, see STRC Signal Peptide Validation)
- ER processing → N-glycosylation of available sites
- GPI attachment → transamidase cleaves at omega site, attaches GPI
- Golgi → glycan maturation
- Surface display → stereocilia tip localization
Steps 2-5 cannot be validated computationally. Require cell-based assays.
N-Glycosylation Sites
Full STRC has 14 predicted N-glycosylation sites (NxS/T sequons).
| Construct | Sites retained | Sites lost | Risk |
|---|---|---|---|
| Full STRC (1-1775) | 14 | 0 | Reference |
| Shorter mini-STRC (700-1775) | 5 (at 824, 916, 964, 1179, 1274) | 9 (res 65-656) | Medium: lost sites may affect folding/trafficking |
| C-term only (1075-1775) | 2 (at 1179, 1274) | 12 | High: minimal glycosylation |
NetNGlyc 1.0 submission pending for confidence scores.
Connections
- STRC Signal Peptide Validation — SP is step 1 of the GPI pathway
[part-of]STRC Mini-STRC Single-Vector Hypothesis — GPI preservation is critical for mini-STRC function[see-also]STRC Hearing Loss — stereocilin function requires membrane anchoring[about]Misha