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Borgert L, Becker T, den Brave F. Conserved quality control mechanisms of mitochondrial protein import. J Inherit Metab Dis 2024. [PMID: 38790152 DOI: 10.1002/jimd.12756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 04/15/2024] [Accepted: 05/08/2024] [Indexed: 05/26/2024]
Abstract
Mitochondria carry out essential functions for the cell, including energy production, various biosynthesis pathways, formation of co-factors and cellular signalling in apoptosis and inflammation. The functionality of mitochondria requires the import of about 900-1300 proteins from the cytosol in baker's yeast Saccharomyces cerevisiae and human cells, respectively. The vast majority of these proteins pass the outer membrane in a largely unfolded state through the translocase of the outer mitochondrial membrane (TOM) complex. Subsequently, specific protein translocases sort the precursor proteins into the outer and inner membranes, the intermembrane space and matrix. Premature folding of mitochondrial precursor proteins, defects in the mitochondrial protein translocases or a reduction of the membrane potential across the inner mitochondrial membrane can cause stalling of precursors at the protein import apparatus. Consequently, the translocon is clogged and non-imported precursor proteins accumulate in the cell, which in turn leads to proteotoxic stress and eventually cell death. To prevent such stress situations, quality control mechanisms remove non-imported precursor proteins from the TOM channel. The highly conserved ubiquitin-proteasome system of the cytosol plays a critical role in this process. Thus, the surveillance of protein import via the TOM complex involves the coordinated activity of mitochondria-localized and cytosolic proteins to prevent proteotoxic stress in the cell.
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Affiliation(s)
- Lion Borgert
- Faculty of Medicine, Institute of Biochemistry and Molecular Biology, University of Bonn, Bonn, Germany
| | - Thomas Becker
- Faculty of Medicine, Institute of Biochemistry and Molecular Biology, University of Bonn, Bonn, Germany
| | - Fabian den Brave
- Faculty of Medicine, Institute of Biochemistry and Molecular Biology, University of Bonn, Bonn, Germany
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Inada T, Beckmann R. Mechanisms of Translation-coupled Quality Control. J Mol Biol 2024; 436:168496. [PMID: 38365086 DOI: 10.1016/j.jmb.2024.168496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 02/05/2024] [Accepted: 02/12/2024] [Indexed: 02/18/2024]
Abstract
Stalling of ribosomes engaged in protein synthesis can lead to significant defects in the function of newly synthesized proteins and thereby impair protein homeostasis. Consequently, partially synthesized polypeptides resulting from translation stalling are recognized and eliminated by several quality control mechanisms. First, if translation elongation reactions are halted prematurely, a quality control mechanism called ribosome-associated quality control (RQC) initiates the ubiquitination of the nascent polypeptide chain and subsequent proteasomal degradation. Additionally, when ribosomes with defective codon recognition or peptide-bond formation stall during translation, a quality control mechanism known as non-functional ribosomal RNA decay (NRD) leads to the degradation of malfunctioning ribosomes. In both of these quality control mechanisms, E3 ubiquitin ligases selectively recognize ribosomes in distinct translation-stalling states and ubiquitinate specific ribosomal proteins. Significant efforts have been devoted to characterize E3 ubiquitin ligase sensing of ribosome 'collision' or 'stalling' and subsequent ribosome is rescued. This article provides an overview of our current understanding of the molecular mechanisms and physiological functions of ribosome dynamics control and quality control of abnormal translation.
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Affiliation(s)
- Toshifumi Inada
- Division of RNA and Gene Regulation, Institute of Medical Science, The University of Tokyo, Minato-Ku, Tokyo 108-8639, Japan.
| | - Roland Beckmann
- Gene Center and Department of Biochemistry, Feodor-Lynen-Str. 25, University of Munich, 81377 Munich, Germany.
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Svetlov MS, Dunand CF, Nakamoto JA, Atkinson GC, Safdari HA, Wilson DN, Vázquez-Laslop N, Mankin AS. Peptidyl-tRNA hydrolase is the nascent chain release factor in bacterial ribosome-associated quality control. Mol Cell 2024; 84:715-726.e5. [PMID: 38183984 DOI: 10.1016/j.molcel.2023.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 11/08/2023] [Accepted: 12/01/2023] [Indexed: 01/08/2024]
Abstract
Rescuing stalled ribosomes often involves their splitting into subunits. In many bacteria, the resultant large subunits bearing peptidyl-tRNAs are processed by the ribosome-associated quality control (RQC) apparatus that extends the C termini of the incomplete nascent polypeptides with polyalanine tails to facilitate their degradation. Although the tailing mechanism is well established, it is unclear how the nascent polypeptides are cleaved off the tRNAs. We show that peptidyl-tRNA hydrolase (Pth), the known role of which has been to hydrolyze ribosome-free peptidyl-tRNA, acts in concert with RQC factors to release nascent polypeptides from large ribosomal subunits. Dislodging from the ribosomal catalytic center is required for peptidyl-tRNA hydrolysis by Pth. Nascent protein folding may prevent peptidyl-tRNA retraction and interfere with the peptide release. However, oligoalanine tailing makes the peptidyl-tRNA ester bond accessible for Pth-catalyzed hydrolysis. Therefore, the oligoalanine tail serves not only as a degron but also as a facilitator of Pth-catalyzed peptidyl-tRNA hydrolysis.
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Affiliation(s)
- Maxim S Svetlov
- Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA; Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA.
| | - Clémence F Dunand
- Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA; Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Jose A Nakamoto
- Department of Experimental Medicine, University of Lund, 221 00 Lund, Sweden
| | - Gemma C Atkinson
- Department of Experimental Medicine, University of Lund, 221 00 Lund, Sweden
| | - Haaris A Safdari
- Institute for Biochemistry and Molecular Biology, University of Hamburg, 20146 Hamburg, Germany
| | - Daniel N Wilson
- Institute for Biochemistry and Molecular Biology, University of Hamburg, 20146 Hamburg, Germany
| | - Nora Vázquez-Laslop
- Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA; Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Alexander S Mankin
- Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA; Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA.
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