Recombinant vault nanoparticle: a potential tool for the targeted delivery of siRNA as therapeutic molecules

Vaults are eukaryotic ribonucleoproteic particles involved in several cellular processes, with promising application as nano-vector of therapeutic molecules. Here, the yeast K. phaffii has been used to constitutively express human recombinant vaults, subsequently purified by size exclusion chromatography, following a simple procedure we optimized. Purified recombinant vaults display the same morphology, size, and biological properties than their natural counterpart, as shown by transmission electron microscopy and dynamic light scattering analysis. To promote antibody-mediated vault targeting, a Z peptide-fused vault variant that selectively binds the constant portion of antibodies has been produced. Vault-Z particle has been proved to enable vault-antibody direct binding. Thus, we are working to optimize the binding ratio of vault-Z variant to antibodies against different cell-type specific receptor, to improve vault uptake. Small interfering RNAs have promising pharmacological potential but its realization depends on their ability to reach their targets in vivo. We are currently attempting to load vault-Z with siRNAs targeting LADON, a lncRNA known to promote tumour progression and invasion in melanoma. SiRNAs are loaded into the vaults by a chemical conjugation to the interaction domain (INT) domain, which is known to bind tightly to vault inner cavity. Vault complexes carrying anti-LADON siRNAs will then be used to target melanoma cells, where their ability to decrease LADON expression and LADON-dependent effects will be tested.