IF PEGylated MTS-WRAP5 cell-penetrating peptide nanocomplexes (N/P ratio 10:1, 2 µg plasmid per well, re-dosed every 72 hours for 14 days) loaded with a codon-optimized nuclear ND1 construct bearing a bipartite mitochondrial targeting sequence — combining the canonical COX8A leader with an appended MPP (mitochondrial processing peptidase) consensus cleavage motif engineered from the CAMP design principle (R-2 rule: Arg at position −2 relative to cleavage site) — are delivered to ARPE-19 cells harboring the m.3460G>A mutation and to ND1-depleted cybrids,

THEN ≥70% restoration of spectrophotometric Complex I enzymatic activity, ≥50 pmol O₂/min/10⁶ cells increase in OCR (Seahorse XF), restoration of ATP synthesis to ≥80% of wild-type levels, and crucially, re-emergence of the CI/CIII respiratory supercomplex band on Blue Native PAGE (BN-PAGE) in-gel activity assay will be observed by week 6 — with functional rescue magnitude equaling or exceeding single-dose AAV2-ND1 (10⁹ vg/well) at the same timepoint —

BECAUSE the following mechanistic chain operates:

1. PEGylation of WRAP5 nanocomplexes reduces non-specific aggregation and extends extracellular stability, permitting repeated dosing every 72 hours to offset protein turnover; the CAMP paper establishes that computationally designed CPP-MTS fusions with cationic amino acid content of ~15–70% mediate efficient cellular uptake and mitochondrial targeting, validating the general CPP-MTS architecture for macromolecular mitochondrial cargo delivery (Cell-penetrating artificial mitochondria-targeting peptide)[https://doi.org/10.1038/s12276-018-0124-z]. [SPECULATIVE: direct PEGylation data for WRAP5 is absent from the current evidence set; PEG effects on uptake are inferred from general CPP nanocomplex literature]

2. The bipartite COX8A + MPP-optimized cleavage motif on the encoded ND1 fusion protein dramatically enhances the probability of mitochondrial matrix import compared to COX8A alone; the CAMP study demonstrates that inclusion of an MPP processing site within the MTS substantially increases predicted mitochondrial-targeting probability across diverse cargo constructs, and that the MPP cleavage functions as a molecular ratchet preventing retrograde translocation of partially imported hydrophobic cargo (CAMP MPP processing site enhances mitochondrial import)[https://doi.org/10.1038/s12276-018-0124-z]. This directly addresses the canonical barrier to allotopic ND1 expression: the extreme hydrophobicity of the ND1 protein that impedes TIM23 channel threading.

3. Codon optimization of the nuclear-encoded ND1 construct is non-negotiable for achieving adequate steady-state mRNA and translated protein levels; the codon optimization study demonstrates that only codon-optimized (not wild-type mitochondrial codon) constructs generate detectable allotopic protein and restore Complex I function, and that CI/CIII supercomplex reassembly — not merely isolated CI enzymatic activity — i...

SENS category: LysoSENS

Key references: • doi.org/10.1038/s12276-018-0124-z]. • doi.org/10.1016/j.redox.2020.101429]. • doi.org/10.1038/s41434-022-00333-6]. • doi.org/10.1038/s41434-022-00333-6 • doi.org/10.1038/s12276-018-0124-z];