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Porin / VDAC acts as a coupling factor to stimulate the import of carrier proteins into the inner mitochondrial membrane. Credit: Becker and Pfanner working groups
The research laboratories of Drs. Thomas Becker and Nikolaus Pfanner of the Institute of Biochemistry and Molecular Biology of the University of Freiburg have reported a function of the mitochondria outer membrane metabolic pathway in protein transport. The researchers published their findings in Molecular cell.
Mitochondria play a fundamental role in the metabolism of the cell. They produce the main energy for cellular functions and are therefore known as the central cell. The defects of mitochondrial metabolism cause a number of serious diseases of the cardiac, muscular or nervous system. The mitochondrial function depends on the exchange of metabolites with the surrounding cell. Therefore, the metabolites must be transported through both surrounding membranes. The porin / VDAC of the voltage-dependent anion channel allows the transfer of metabolites through the outer membrane. The inner membrane is equipped with specific transporters, the carrier proteins, which carry the metabolites through the inner membrane.
Mitochondria also depend on the importation of about 1,000 types of cytosol proteins. The translocase of the outer membrane, also called TOM complex, is the gateway for precursor proteins. The import of carrier proteins is particularly important for mitochondrial metabolism. Carrier precursors pbad the outer membrane via the TOM channel. Subsequently, the auxiliary proteins, the small TIM proteins, guide the precursors towards the inner membrane. The support translocase, the TIM22 complex, integrates the precursors into the inner membrane. The way in which the different stages of transport of the carrier import channel are connected to each other has not been known before.
Researchers at the University of Friborg have discovered an unexpected function of porin / VDAC in metabolite channels in the import of proteins into mitochondria. Dr. Lars Ellerieder of Thomas Becker's research laboratory has shown that porin / VDAC stimulates the import of carrier proteins into the inner membrane. The function of porin / VDAC in protein transport occurs regardless of the activity of its channel. Instead, porin / VDAC acts as a coupling factor. Proteins bind to carrier precursors in the intermembrane space, TOM complex, and carrier translocase. Thus, porin / VDAC spatially links the unique transport steps and thus stimulates the import of carrier proteins.
The researchers demonstrate that the transport of proteins and mitochondrial metabolites are linked: "The role of porin / VDACs in protein transport could represent an elegant mechanism for fine-tuning the import of vector proteins and therefore possibly metabolite transport to meet the needs of the cell, "says Becker
Explore further:
Help transport proteins inside the cell
More information:
Ellenrieder, L et al. (2019): Double role of mitochondrial porin in the transport of metabolites through the outer membrane and the transfer of proteins to the inner membrane. Molecular cell. DOI: 10.1016 / j.molcel.2018.12.014, https://www.cell.com/molecular-cell/fulltext/S1097-2765(18)31068-2
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