title: Increased RNAi is related to intracellular release of siRNA via a covalently attached signal peptide.
abstract: In the last decade short interfering RNA (siRNA) became an important means for functional genomics and the development of gene-specific drugs. However, major technical hurdles in the application of siRNA include its cellular delivery followed by its intracellular trafficking and its release in order to enter the RNA interference (RNAi) machinery. The novel phosphorothioate-stimulated cellular uptake of siRNA contrasts other known delivery systems because it involves a caveosomal pathway in which large amounts of siRNA are delivered to the perinuclear environment, leading to measurable though moderate target suppression. Limited efficacy seems to be related to intracellular trapping of siRNA. To study the role of intracellular trafficking of siRNA for biological effectiveness we studied whether a signal peptide for trans-membrane transport of bacterial protein toxins, which is covalently attached to siRNA, can promote its release from the perinuclear space into the cytoplasm and thereby enhance its biological effectiveness. We show that attachment of the peptide TQIENLKEKG to lamin A/C-directed siRNA improves target inhibition after its PS-stimulated delivery. This is related to increased efflux of the siRNA-peptide conjugate from the ER-specific perinuclear sites. In summary, this study strongly suggests that intracellular release of siRNA leads to increased biological effectiveness. Thus covalent peptide-siRNA conjugates are proposed as new tools to study the relationship between intracellular transport and efficacy of siRNA.
authors.affiliation: Institut für Molekulare Medizin, Universität zu Lübeck and Schleswig-Holstein, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Detzer
authors.forename: Marita
authors.initials: M
authors.lastname: Overhoff
authors.forename: Winfried
authors.initials: W
authors.lastname: Wünsche
authors.forename: Maria
authors.initials: M
authors.lastname: Rompf
authors.forename: John J
authors.initials: JJ
authors.lastname: Turner
authors.forename: Gabriela D
authors.initials: GD
authors.lastname: Ivanova
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gait
authors.forename: Georg
authors.initials: G
authors.lastname: Sczakiel
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D007797:Laminin / Q000235:genetics; D021382:Protein Sorting Signals; D034622:RNA Interference; D034443:RNA Transport; D034741:RNA, Small Interfering / Q000378:metabolism*
chemical_list: D007797:Laminin; D021382:Protein Sorting Signals; D034741:RNA, Small Interfering