Ca and Nε-lysine acetylation regulate the CALR-ATG9A interaction in the lumen of the endoplasmic reticulum.

The acetylation of autophagy protein 9 A (ATG9A) in the lumen of the endoplasmic reticulum (ER) by ATase1 and ATase2 regulates the induction of reticulophagy. Analysis of the ER-specific ATG9A interactome identified calreticulin (CALR), an ER luminal Ca-binding chaperone, as key for ATG9A activity. Specifically, if acetylated, ATG9A is sequestered by CALR and prevented from engaging FAM134B and SEC62.

Development of succinimide-based inhibitors for the mitochondrial rhomboid protease PARL.

While the biochemistry of rhomboid proteases has been extensively studied since their discovery two decades ago, efforts to define the physiological roles of these enzymes are ongoing and would benefit from chemical probes that can be used to manipulate the functions of these proteins in their native settings. Here, we describe the use of activity-based protein profiling (ABPP) technology to conduct a targeted screen for small-molecule inhibitors of the mitochondrial rhomboid protease PARL, which plays a critical role in regulating mitophagy and cell death. We synthesized a series of succinimide-containing sulfonyl esters and sulfonamides and discovered that these compounds serve as inhibitors of PARL with the most potent sulfonamides having submicromolar affinity for the enzyme.

ATG9A regulates proteostasis through reticulophagy receptors FAM134B and SEC62 and folding chaperones CALR and HSPB1.

The acetylation of ATG9A within the endoplasmic reticulum (ER) lumen regulates the induction of reticulophagy. ER acetylation is ensured by AT-1/SLC33A1, a membrane transporter that maintains the cytosol-to-ER flux of acetyl-CoA. Defective AT-1 activity, as caused by heterozygous/homozygous mutations and gene duplication events, results in severe disease phenotypes.