Abstract
Ferroptosis is a type of iron-dependent regulated cell death caused by the disruption that occurs when oxidative stress and antioxidant defenses interact, and then driven by lipid peroxidation and subsequent plasma membrane ruptures. The regulation of ferroptosis involves many factors, including the crosstalk between subcellular organelles, such as mitochondria, endoplasmic reticulum (ER), lysosomes, lipid droplets, and peroxisomes. Here, we show that the ER protein STING1 (also known as STING or TMEM173) promotes ferroptosis in human pancreatic cancer cell lines by increasing MFN1/2-dependent mitochondrial fusion, but not mitophagy-mediated mitochondrial removal. The classic ferroptosis inducer erastin, but not sulfasalazine, induces the accumulation of STING1 in the mitochondria, where it binds to MFN1/2 to trigger mitochondrial fusion, leading to subsequent reactive oxygen species production and lipid peroxidation. Consequently, in vitro or xenograft mouse models show that the genetic depletion of STING1 or MFN1/2 (but not the mitophagy regulator PINK1 or PRKN) reduces the sensitivity of pancreatic cancer cells to ferroptosis. These findings not only establish a new mitochondrial fusion-dependent cell death mechanism, but also indicate a potential strategy for enhancing ferroptosis-based therapy.
Highlights
Mitochondria are dynamic membrane-bound organelles that are the main site of energy metabolism, and participate in various cell signal transduction processes by regulating oxidative stress and calcium homeostasis (Friedman and Nunnari, 2014)
In the study described here, we provide the first evidence that STING1 promotes erastin-induced ferroptosis in human pancreatic cancer cell lines by promoting mitochondrial fusion via binding to mitofusins, which are key regulators of mitochondrial dynamics
Since the endoplasmic reticulum (ER) membrane and mitochondrial membrane are in close contact during cell stresses (Bravo-Sagua et al, 2013), we first investigated whether the ER protein STING1 can be translocated to mitochondria in PANC1, a human pancreatic ductal adenocarcinoma (PDAC) cell line that expresses STING1 and is sensitive to ferroptosis (Zhu et al, 2017; Li C. et al, 2020)
Summary
Mitochondria are dynamic membrane-bound organelles that are the main site of energy metabolism, and participate in various cell signal transduction processes by regulating oxidative stress and calcium homeostasis (Friedman and Nunnari, 2014). Mitochondria are altered through balanced fission and fusion. Once this dynamic balance is broken, the mitochondria may show functional changes, and even defects (Giacomello et al, 2020). The destruction of mitochondrial dynamic regulation can lead to a variety of diseases, including cancer (Giacomello et al, 2020). Understanding the mechanism and regulation of mitochondrial dynamics may lead to the development of new cancer treatment strategies
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