Year: 2015
Type: article
Abstract: Myoglobin and mitochondria have been studied extensively over the past century; however, the mechanisms by which they interact still remain unclear. Myoglobin is known for its localization in skeletal muscle where it stores and transports oxygen to respiring mitochondria. Myoglobin is now gaining recognition for its expression in cancer and its function as a nitrite reductase, able to reduce nitrite to nitric oxide (NO). The overall objective of this study is to characterize the regulation of mitochondria by myoglobin, specifically in ischemia/reperfusion injury and breast cancer. Mitochondrial damage is a central component to ischemia/reperfusion injury. Nitrite is known to mediate protection after ischemia/reperfusion through its reduction to NO, which S-nitrosates complex I of the electron transport chain. This S-nitrosation reduces reactive oxygen species generation, thereby reducing cell death. Using myoglobin positive and negative cells, this study shows that nitrite is only able to mediate protection in myoglobin-expressing cells through S-nitrosation. Furthermore, by knocking down complex I by siRNA transfection, it is confirmed that this protection occurs through complex I. Therefore, myoglobin expression is required for nitrite to have protective effects in reperfusion injury. Myoglobin has only recently been discovered in cancer tumors; therefore, little is known about its function in these tissues. Interestingly, myoglobin expression in breast cancer has been associated with better patient prognosis. In this study, stable transfection of myoglobin in MDA-MB-231 breast cancer cells caused a significant decrease in cell proliferation and marked mitochondrial fusion. This fusion of mitochondria resulted in cell cycle arrest at the G1/S phase transition of the cell cycle. Further investigation showed that myoglobin expression prevents ubiquitination of mitochondrial fusion proteins. Myoglobin-expressing cells therefore have extensive mitochondrial fusion, which causes cell cycle arrest and reduced cell proliferation and tumor growth in vivo. This project has identified that myoglobin is necessary for nitrite to have protective effects in ischemia/reperfusion and begun to elucidate the mechanism by which myoglobin is beneficial in breast cancer. With further research, myoglobin may be used as a therapeutic target for cancer as well as ischemia/reperfusion in other tissues.
Author: Janelle Bickta
Language: English
Subfield: Biochemistry
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W804851436