Abstract
BACKGROUND
Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE+HS) exhibits a "proteostatic crisis" where oxidative stress defense is compromised. Vital neuroprotective proteins regulating oxidative stress pathways, OXR1 (Oxidation Resistance 1) and GLRX (Glutaredoxin), have been identified by multi-omics studies as consistently downregulated in affected tissue. While rare OXR1 loss-of-function mutations cause severe neurological phenotypes, the common MTLE downregulation may involve post-translational modifications (PTMs). This study computationally predicts ubiquitination, acetylation, phosphorylation, and SUMOylation sites in OXR1 and GLRX.
METHODS
Canonical sequences for human OXR1 and GLRX plus orthologs (mouse, rat, zebrafish) were obtained from UniProt. Clustal Omega performed multiple sequence alignments; Scorecons calculated per-residue conservation (0-1 scale; ≥0.7 = highly conserved). MusiteDeep predicted PTM sites for ubiquitination, phosphorylation, acetylation, and SUMOylation (≥0.5 retained; ≥0.7 = high-confidence).
RESULTS
OXR1 showed 62% high conservation (550/884 residues ≥0.7), concentrated in the TLDc domain. GLRX exhibited 96% conservation (103/107 residues), including perfect scores across the glutaredoxin domain and CXXC active site.
OXR1 displayed dominant phosphorylation predictions (ten sites ≥0.85) and K385 SUMOylation (0.897). Top-scoring sites showed moderate conservation (0.58-0.62), below threshold. Phosphorylation clusters at positions 161-168 and 201-204 suggest multi-site regulation.
GLRX predictions were sparse but functionally relevant: K20 acetylation (0.645, conservation 1.0) sits two residues from the CXXC active site; K39 ubiquitination (0.582, conservation 1.0) lies within the domain core. Both sites showed perfect evolutionary conservation despite moderate prediction scores.
DISCUSSION
GLRX's perfectly conserved K20/K39 sites could disrupt redox function if dysregulated, impairing glutathione-dependent antioxidant pathways in TLE. K20's proximity to the catalytic CXXC motif suggests acetylation could sterically block substrate binding, contributing to proteostatic crisis. OXR1's high-scoring sites occupy moderately conserved regions, potentially representing lineage-specific regulation. However, moderate-confidence PTMs within the highly conserved TLDc domain warrant validation. Phosphorylation dominance suggests kinase-mediated regulation responsive to oxidative stress.
Predictions require mass spectrometry validation in MTLE+HS tissue; priority validation candidates include GLRX K20/K39 and OXR1 TLDc domain sites with high PTM scores and conservation. Cross-referencing with TLE proteomics could identify disease-relevant modifications, revealing therapeutic targets beyond ion channels.
