page_title: Mitochondrial biogenesis
section_title: Protein import
hierarchical_section_title: Mitochondrial biogenesis / Protein import
context_page_description: Mitochondrial biogenesis is the process by which cells increase mitochondrial mass. It was first described by John Holloszy in the 1960s, when it was discovered that physical endurance training induced higher mitochondrial content levels, leading to greater glucose uptake by muscles. Mitochondrial biogenesis is activated by numerous different signals during times of cellular stress or in response to environmental stimuli, such as aerobic exercise.
context_section_description: Since the majority of mitochondrial protein comes from the nuclear genome, the proteins need to be properly targeted and transported into the mitochondria to perform their functions. First, mRNA is translated in the cell’s cytosol. The resulting unfolded precursor proteins will then be able to reach their respective mitochondrial compartments. Precursor proteins will be transported to one of four areas of the mitochondria, which include the outer membrane, inner membrane, intermembrane space, and matrix. All proteins will enter the mitochondria by a translocase on the outer mitochondrial membrane (TOM). Some proteins will have an N-terminal targeting signal, and these proteins will be detected and transported into the matrix, where they will then be cleaved and folded. Other proteins may have targeting information in their sequences and will not include an N-terminal signal. During the past two decades, researchers have discovered over thirty proteins that participate in mitochondrial protein import. As researchers learn more about these proteins and how they reach the respective mitochondrial compartments that utilize them, it becomes evident that there is a multitude of processes that work together in the cell to allow for mitochondrial biogenesis.
caption: Mitochondrial proteins encoded from the nuclear genome need to be targeted and transported appropriately into the mitochondria.