Mitochondria are the powerhouses of cells, and they are always changing shape. Why they do this has been a mystery. Scientists looked at yeast cells growing in different foods. They found that the shape of mitochondria and their activity do not go hand in hand. Cells can have different mitochondrial shapes in various food environments, regardless of how active the mitochondria are.

The key player here is the cell's redox state. This is a balance between molecules that can give or take electrons. The redox state depends on how electrons enter the electron transport chain (ETC). This can happen through complex I or II, or directly to coenzyme Q or cytochrome c. When electrons enter the ETC directly, reactive oxygen species (ROS) go up. This leads to an oxidized environment in the cell. As a result, mitochondria quickly break apart into fragments.

Now, if the direct entry of electrons into the ETC is reduced, either by genetic or chemical means, or if the cell's environment is made less oxidized, the mitochondria quickly form networks again. By controlling the flow of electrons, scientists showed that they could switch between networked and fragmented mitochondria in just minutes. This happened without changing the mitochondria's activity.

The machinery that controls this shape-shifting is called Dnm1. It responds to changes in the redox state in just minutes, before the mitochondria change shape. So, the cell's metabolic state and its redox state are the real bosses when it comes to the shape of mitochondria.

This discovery is a big deal. It shows that the shape of mitochondria is not just random. It is controlled by the cell's metabolism and redox state. This could have big implications for understanding diseases where mitochondria are involved. For instance, cancer cells often have different mitochondrial shapes. Understanding why this happens could lead to new treatments.

The study also raises questions. If the shape of mitochondria is so important, why do cells change it so much? And how do other organelles respond to these changes? These are questions for future research. But one thing is clear: the shape of mitochondria is not just a passive process. It is actively controlled by the cell.

MITOCHONDRIAL MORPHOLOGY

How Cells Shape Their Powerhouses

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