bims-mitpro 2024-10-06 papers

Issue of 2024–10–06
three papers selected by
Andreas Kohler, Umeå University

FEBS Open Bio. 2024 Oct;14(10): 1595-1609

Biogenesis of mitochondrial β-barrel membrane proteins.

Iniyan Ganesan, Jon V Busto, Nikolaus Pfanner, Nils Wiedemann.

β-barrel membrane proteins in the mitochondrial outer membrane are crucial for mediating the metabolite exchange between the cytosol and the mitochondrial intermembrane space. In addition, the β-barrel membrane protein subunit Tom40 of the translocase of the outer membrane (TOM) is essential for the import of the vast majority of mitochondrial proteins encoded in the nucleus. The sorting and assembly machinery (SAM) in the outer membrane is required for the membrane insertion of mitochondrial β-barrel proteins. The core subunit Sam50, which has been conserved from bacteria to humans, is itself a β-barrel protein. The β-strands of β-barrel precursor proteins are assembled at the Sam50 lateral gate forming a Sam50-preprotein hybrid barrel. The assembled precursor β-barrel is finally released into the outer mitochondrial membrane by displacement of the nascent β-barrel, termed the β-barrel switching mechanism. SAM forms supercomplexes with TOM and forms a mitochondrial outer-to-inner membrane contact site with the mitochondrial contact site and cristae organizing system (MICOS) of the inner membrane. SAM shares subunits with the ER-mitochondria encounter structure (ERMES), which forms a membrane contact site between the mitochondrial outer membrane and the endoplasmic reticulum. Therefore, β-barrel membrane protein biogenesis is closely connected to general mitochondrial protein and lipid biogenesis and plays a central role in mitochondrial maintenance.

Keywords: Mco6; Mdm10; SAM; Sam35; Sam37; Sam50; mitochondria; outer membrane; sorting and assembly machinery; β‐barrel protein

DOI: https://doi.org/10.1002/2211-5463.13905

Nat Cell Biol. 2024 Oct 02.

The role of PINK1-Parkin in mitochondrial quality control.

Derek P Narendra, Richard J Youle.

Mitophagy mediated by the recessive Parkinson's disease genes PINK1 and Parkin responds to mitochondrial damage to preserve mitochondrial function. In the pathway, PINK1 is the damage sensor, probing the integrity of the mitochondrial import pathway, and activating Parkin when import is blocked. Parkin is the effector, selectively marking damaged mitochondria with ubiquitin for mitophagy and other quality-control processes. This selective mitochondrial quality-control pathway may be especially critical for dopamine neurons affected in Parkinson's disease, in which the mitochondrial network is widely distributed throughout a highly branched axonal arbor. Here we review the current understanding of the role of PINK1-Parkin in the quality control of mitophagy, including sensing of mitochondrial distress by PINK1, activation of Parkin by PINK1 to induce mitophagy, and the physiological relevance of the PINK1-Parkin pathway.

DOI: https://doi.org/10.1038/s41556-024-01513-9

Cell Rep. 2024 Oct 02. pii: S2211-1247(24)01154-9. [Epub ahead of print]43(10): 114803

Temporal alterations of the nascent proteome in response to mitochondrial stress.

Tomasz M Stępkowski, Vanessa Linke, Dorota Stadnik, Maciej Zakrzewski, Anna E Zawada, Remigiusz A Serwa, Agnieszka Chacinska.

Under stress, protein synthesis is attenuated to preserve energy and mitigate challenges to protein homeostasis. Here, we describe, with high temporal resolution, the dynamic landscape of changes in the abundance of proteins synthesized upon stress from transient mitochondrial inner membrane depolarization. This nascent proteome was altered when global translation was attenuated by stress and began to normalize as translation was recovering. This transition was associated with a transient desynchronization of cytosolic and mitochondrial translation and recovery of cytosolic and mitochondrial ribosomal proteins. Further, the elongation factor EEF1A1 was downregulated upon mitochondrial stress, and its silencing mimicked the stress-induced nascent proteome remodeling, including alterations in the nascent respiratory chain proteins. Unexpectedly, the stress-induced alterations in the nascent proteome were independent of physiological protein abundance and turnover. In summary, we provide insights into the physiological and pathological consequences of mitochondrial function and dysfunction.

Keywords: CP: Cell biology; CP: Metabolism; EEF1A; EEF1A1; cellular stress; elongation factor; mass spectrometry; mitochondria; nascent chain; protein synthesis; proteomics; translation

DOI: https://doi.org/10.1016/j.celrep.2024.114803