GCN5L1 interacts with αTAT1 and RanBP2 to regulate hepatic α-tubulin acetylation and lysosome trafficking

Although GCN5L1 facilitates mitochondrial protein acetylation and controls endosomal-lysosomal trafficking mechanisms underpinning these disparate effects are unclear. As microtubule acetylation modulates endosome-lysosome trafficking we reasoned that exploring the role of GCN5L1 in this biology may enhance our understanding of GCN5L1-mediated protein acetylation. We show that α-tubulin acetylation is reduced in GCN5L1 knockout hepatocytes and restored by GCN5L1 reconstitution. Furthermore, GCN5L1 binds to the alpha-tubulin acetyltransferase αTAT1 and GCN5L1 mediated α-tubulin acetylation is αTAT1-dependent. Given that cytosolic GCN5L1 has been identified as a component of numerous multiprotein complexes, we explored whether novel interacting partners contribute to this regulation. We identify RanBP2 as a novel interacting partner of GCN5L1 and αTAT1. Genetic silencing of RanBP2 phenocopies GCN5L1 depletion by reducing α-tubulin acetylation and we find that RanBP2 possesses a tubulin binding domain which recruits GCN5L1 to α-tubulin. Finally, genetic depletion of GCN5L1 promotes perinuclear lysosome accumulation and histone deacetylase inhibition partially restores lysosomal positioning. We conclude that the interactions of GCN5L1, RanBP2 and αTAT1 function in concert to control α-tubulin acetylation and may contribute towards the regulation of cellular lysosome positioning.