Scientists found that mitochondria in skeletal muscle form networks, fuse, and share components. Flaws in this process may contribute to muscle disorders.
Skeletal muscles are made of long fibers packed with many highly organized proteins and organelles. Nestled among the protein machinery responsible for muscle contraction are mitochondria. These globular-shaped organelles provide energy for muscle and also help regulate the calcium signals that trigger muscle contraction.
Mitochondria undergo constant change. Defective parts are removed and replaced with new ones. Mitochondria can repair themselves through a process called mitochondrial fusion—joining with other mitochondria and exchanging material.
The mitochondria in muscle, however, were presumed to be fairly isolated with little ability to interact with each other, due to the tissue’s compact organization.
The team examined several mitochondrial proteins that are involved with fusion and may play a role in some muscle disorders. They found that fusion depended on the presence of mitofusin 1 (Mfn1), a protein located on the outer membrane of mitochondria.
In further experiments, the group found that disruptions in Mfn1 and fusion led to abnormal calcium regulation in mitochondria. Calcium signaling problems might thus account for defects in muscle function, such as fatigue.