VPS26A Subunit Enhancement to Stabilize Retromer Complex Assembly

This hypothesis proposes that targeted enhancement of VPS26A subunit expression and stability can rescue retromer complex dysfunction by improving the structural integrity and assembly efficiency of the VPS26/VPS29/VPS35 heterotrimer. Unlike approaches focusing on VPS35 restoration, this strategy targets the cargo recognition subunit VPS26A, which serves as the critical interface between the retromer core and cargo-selective sorting nexins. The mechanism involves VPS26A-mediated stabilization of the entire retromer complex through enhanced protein-protein interactions at the endosomal membrane. Specifically, increased VPS26A levels would promote more robust binding between the cargo recognition domain and sorting nexin dimers (SNX1/SNX2 or SNX5/SNX6), leading to improved retrograde transport from endosomes to the trans-Golgi network. This approach addresses the fundamental assembly defects observed in neurodegenerative diseases where retromer dysfunction contributes to pathological protein accumulation. The intervention would utilize VPS26A overexpression vectors or small molecule stabilizers that enhance VPS26A folding and membrane recruitment. Evidence would focus on measuring retromer complex stability through co-immunoprecipitation assays, tracking cargo trafficking efficiency using fluorescent protein reporters, and quantifying endosomal morphology changes via electron microscopy. Success metrics include increased retromer complex half-life, restored mannose-6-phosphate receptor recycling, and reduced endosomal enlargement phenotypes. This VPS26A-centric approach offers a complementary strategy to VPS35-focused therapies by targeting the rate-limiting step of retromer assembly and cargo recognition specificity.