Cytotoxic activities of several Golgi-dispersing compounds including AMF-26/M-COPA, brefeldin A and golgicide A have previously been shown to induce autophagy or apoptosis. Here, we demonstrate that these Golgi disruptors also trigger ferroptosis, a non-apoptotic form of cell death characterized by iron-dependent oxidative degradation of lipids. Inhibitors of ferroptosis not only counteract cell death, but they also protect from Golgi dispersal and inhibition of protein secretion in response to several Golgi stress agents. Furthermore, the application of sublethal doses of ferroptosis-inducers such as erastin and sorafenib, low cystine growth conditions, or genetic knockdown of SLC7A11 and GPX4 all similarly protect cells from Golgi stress and lead to modulation of ACSL4, SLC7A5, SLC7A11 or GPX4 levels. Collectively, this study suggests a previously unrecognized function of the Golgi apparatus, which involves cellular redox control and prevents ferroptotic cell death.

Tether complexes play important roles in endocytic and exocytic trafficking of lipids and proteins. In yeast, the multisubunit transport protein particle (TRAPP) tether regulates endoplasmic reticulum (ER)-to-Golgi and intra-Golgi transport and is also implicated in autophagy. In addition, the TRAPP complex acts as a guanine nucleotide exchange factor (GEF) for Ypt1, which is homologous to human Rab1a and Rab1b. Here, we show that human TRAPPC13 and other TRAPP subunits are critically involved in the survival response to several Golgi-disrupting agents. Loss of TRAPPC13 partially preserves the secretory pathway and viability in response to brefeldin A, in a manner that is dependent on ARF1 and the large GEF GBF1, and concomitant with reduced caspase activation and ER stress marker induction. TRAPPC13 depletion reduces Rab1a and Rab1b activity, impairs autophagy and leads to increased infectivity to the pathogenic bacterium in response to brefeldin A. Thus, our results lend support for the existence of a mammalian TRAPPIII complex containing TRAPPC13, which is important for autophagic flux under certain stress conditions.

The Golgi apparatus is part of the secretory pathway and of central importance for modification, transport and sorting of proteins and lipids. ADP‐ribosylation factors, whose activation can be blocked by brefeldin A (BFA), play a major role in functioning of the Golgi network and regulation of membrane traffic and are also involved in proliferation and migration of cancer cells. Due to high cytotoxicity and poor bioavailability, BFA has not passed the preclinical stage of drug development. Recently, AMF‐26 and golgicide A have been described as novel inhibitors of the Golgi system with antitumor or bactericidal properties. We provide here further evidence that AMF‐26 closely mirrors the mode of action of BFA but is less potent. Using several human cancer cell lines, we studied the effects of AMF‐26, BFA and golgicide A on cell homeostasis including Golgi structure, endoplasmic reticulum (ER) stress markers, secretion and viability, and found overall a significant correlation between these parameters. Furthermore, modulation of ADP‐ribosylation factor expression has a profound impact on Golgi organization and survival in response to Golgi stress inducers.

Transcriptomic profiling of cells treated with Golgi-disrupting compounds reveals that some target genes including several spliceosome components are controlled by ELK1, GABPA, and ETS1, the activity of which is regulated by MEK/ERK signaling. Furthermore, brefeldin A and golgicide A cause increased splicing of the proapoptotic MCL1-S isoform.

Changes in the transcriptome of cells treated with established Golgi apparatus-dispersing agents were analyzed, and HDAC inhibitors (HDACis) and DNA damage-causing drugs were found to induce similar transcriptional profiles. In parallel, an image-based screen validated HDACis and DNA-damaging agents as novel Golgi disruptors.

No abstract