Endosomal Escape of ASOs Internalized by Stabilin Receptors Is Regulated by Rab5C and EEA1.

Abstract

One of the major drug classes that has been gaining traction in the pharmacological world has been the emergence of Antisense oligonucleotides (ASOs). Increased modifications of these drugs have led to major breakthroughs leading to a boost in this drug class being adapted to clinical trials. Second generation (Gen 2) Antisense oligonucleotides show increased nuclease stability and affinity for their RNA targets which has translated to improved potency and therapeutic index in the clinic. Gen 2 ASOs are typically modified using the phosphorothioate (PS) backbone modification which enhances ASO interactions with plasma, cell surface and intracellular proteins. This facilitates ASO distribution to peripheral tissues and also promotes cellular uptake after injection into animals. Recent work of ours has shown that a group of class H Stabilin receptors specifically internalize PS‐ASOs in the sinusoidal cells of the liver and the spleen. This work identifies a breakthrough candidate for the determination of a molecular pathway for these drugs to reach their desired target in the cell. Further exploration of the endocytotic uptake by these proteins has led to a rudimentary understanding of this pathway. By modulating expression of specific proteins involved in the trafficking and maturation of the endo‐lysosomal compartments, we show that the proteins Rab5C and EEA1 play a direct role in the early endosomal pathway. These proteins, along with Rab7A and LBPA (lyso‐lipid) in the late endosomal pathway, are important for trafficking of PS‐ASOs and facilitate their escape from endo‐lysosomal compartments after Stabilin‐mediated internalization. In conclusion, this research identifies key interacting partners involved in ASO‐containing endosomal maturation, as well as late endosomal partners involved in PS‐ASO endosomal release. This work also identifies the limiting proteins in the pathway for PS‐ASO translocation and escape from the endosome.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.