Mitochondria import about 1000 proteins that are produced as precursors on cytosolic ribosomes. Defects in mitochondrial protein import result in the accumulation of non-imported precursor proteins and proteotoxic stress. The cell is equipped with different quality control mechanisms to monitor protein transport into mitochondria. First, molecular chaperones guide unfolded proteins to mitochondria and deliver non-imported proteins to proteasomal degradation. Second, quality control factors remove translocation stalled precursor proteins from protein translocases. Third, protein translocases monitor protein sorting to mitochondrial subcompartments. Fourth, AAA proteases of the mitochondrial subcompartments remove mislocalized or unassembled proteins. Finally, impaired efficiency of protein transport is an important sensor for mitochondrial dysfunction and causes the induction of cellular stress responses, which could eventually result in the removal of the defective mitochondria by mitophagy. In this review, we summarize our current understanding of quality control mechanisms that govern mitochondrial protein transport.
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Cover Image
Cover Image
Parp7 is part of an androgen signaling axis that controls its expression in prostate cancer cells. Kamata and colleagues (pp. 2999–3014) show that Parp7 selectively ADP-ribosylates the agonist conformation of the androgen receptor (AR). The cover image shows nuclear localization of Parp7 (red) and AR (green) in prostate cancer cells using confocal scanning microscopy. Co-localization of Parp7 and AR (yellow) and DAPI staining of DNA (blue) is also shown. Image provided by Natalia Dworak, Chun-Song Yang, and Bryce Paschal.
Quality control of protein import into mitochondria
Fabian den Brave, Jeannine Engelke, Thomas Becker; Quality control of protein import into mitochondria. Biochem J 27 August 2021; 478 (16): 3125–3143. doi: https://doi.org/10.1042/BCJ20190584
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