Two Endoplasmic Reticulum (ER)/ER Golgi Intermediate Compartment-based Lysine Acetyltransferases Post-translationally Regulate BACE1 Levels

We have recently identified a novel form of post-translational regulation of BACE1(beta-site amyloid precursor protein-cleaving enzyme 1), a membrane protein that acts as the rate-limiting enzyme in the generation of the Alzheimer disease amyloid beta-peptide. Specifically, nascent BACE1 is transiently acetylated in seven lysine residues clustered in a highly disordered region of the protein that faces the lumen of the endoplasmic reticulum (ER)/ER Golgi intermediate compartment (ER/ERGIC). The acetylation protects the nascent protein from degradation by PCSK9/NARC-1 in the ERGIC and allows it to reach the Golgi apparatus. Here we report the identification of two ER/ERGIC-based acetyltransferases, ATase1 and ATase2. Both proteins display acetyl-CoA: lysine acetyltransferase activity, can interact with and acetylate BACE1, and display an ER/ERGIC localization with the catalytic site facing the lumen of the organelle. Both ATase1 and ATase2 regulate the steady-state levels of BACE1 and the rate of amyloid beta-peptide generation. Finally, their transcripts are up-regulated by ceramide treatment. In conclusion, our studies have identified two new enzymes that may be involved in the pathogenesis of late-onset Alzheimer disease. The biochemical characterization of the above events could lead to the identification of novel pharmacological strategies for the prevention of this form of dementia.