bims-tricox 2026-03-01 papers

Issue of 2026–03–01
two papers selected by
Yash Verma, Universität Zürich

Nat Cell Biol. 2026 Feb 26.

Mitochondria contact lipid droplets through the mitochondrial import complex binding to lipid metabolism enzyme Ayr1.

Mitochondria play central roles in the energetics and metabolism of eukaryotic cells. Their outer membrane is essential for protein transport, membrane dynamics, signalling and metabolic exchange with other cellular compartments. The mitochondrial import (MIM) complex functions as main translocase for importing the precursors of more than 90% of integral outer-membrane proteins. Here we report that the MIM complex performs a second major function in lipid-droplet homeostasis. Lipid droplets are crucial in cellular lipid metabolism and as storage organelles for neutral lipids. The lipid metabolism enzyme Ayr1 captures the MIM complex, promoting the formation of mitochondria-lipid droplet contact sites. MIM and Ayr1 enhance the lipid droplet number in cells. Ayr1 binds to MIM via its single hydrophobic segment in a substrate-mimicry mechanism but remains bound and is not released into the outer membrane. The functional diversity is mediated by different MIM complexes: MIM-Ayr1 for recruiting lipid droplets and MIM-preprotein for protein insertion into the outer membrane. Our work uncovers translocase capture as a mechanism for functional conversion of a membrane protein complex from protein insertion to lipid metabolism.

DOI: https://doi.org/10.1038/s41556-026-01890-3

Nat Struct Mol Biol. 2026 Feb 27.

Stress adaptation of mitochondrial protein import by OMA1-mediated degradation of DNAJC15.

Lara Kroczek, Hendrik Nolte, Yvonne Lasarzewski, Ishita Agrawal, Thibaut Molinié, Daniel Curbelo Piñero, Kathrin Lemke, Elena Rugarli, Thomas Langer.

Mitochondria dynamically adapt to cellular stress to ensure cell survival. The stress-regulated mitochondrial peptidase OMA1 orchestrates these adaptive responses, which limit mitochondrial fusion and promote mitochondrial stress signaling and metabolic rewiring. Here, we show that cellular stress adaptation involves OMA1-mediated regulation of mitochondrial protein import and OXPHOS biogenesis. OMA1 cleaves the mitochondrial chaperone DNAJC15 and promotes its degradation by the m-AAA protease AFG3L2. Loss of DNAJC15 impairs mitochondrial protein import and restricts OXPHOS biogenesis under conditions of mitochondrial dysfunction. Non-imported mitochondrial preproteins accumulate at the endoplasmic reticulum, inducing an unfolded protein response. Our results demonstrate stress-dependent changes in mitochondrial protein import as part of the OMA1-mediated mitochondrial stress response and highlight the interdependence of proteostasis regulation between different organelles.

DOI: https://doi.org/10.1038/s41594-026-01756-0