bims-mitpro 2025-07-13 papers

Issue of 2025–07–13
three papers selected by
Andreas Kohler, Umeå University

J Cell Sci. 2025 Jul 01. pii: jcs263701. [Epub ahead of print]138(13):

MitoRUSH as a tool to study the efficiency of mitochondrial import in complex I-deficient cells.

Michal Wasilewski, Karthik Mohanraj, Maciej Zakrzewski, Remigiusz A Serwa, Agnieszka Chacinska.

Most mitochondrial proteins are imported through the actions of the presequence translocase of the inner membrane, the TIM23 complex, which requires energy in the form of the electrochemical potential of the inner membrane and ATP. Conversions of energy in mitochondria are disturbed in mitochondrial disorders that affect oxidative phosphorylation. Despite the widely accepted dependence of protein import into mitochondria on mitochondrial bioenergetics, effects of mitochondrial disorders on biogenesis of the mitochondrial proteome are poorly characterized. Here, we describe molecular tools that can be used to explore mitochondrial protein import in intact cells, the mitoRUSH assay, and a novel method based on labeling of nascent proteins with an amino acid analog and click chemistry. Using these orthogonal approaches, we discovered that defects in the electron transport chain and manipulating the expression of TIMM23, as well as the TIMM17A or TIMM17B paralogs, in human cells are associated with a decrease in protein import into mitochondria. We postulate that in the absence of a functional electron transfer chain, the mechanisms that support electrochemical potential of the inner membrane and ATP production are insufficient to sustain the import of proteins to mitochondria.

Keywords: Bioenergetics; Mitochondria; Mitochondrial diseases; Protein import; TIM23; Translocase; mitoRUSH

DOI: https://doi.org/10.1242/jcs.263701

FASEB Bioadv. 2025 Jul;7(7): e70030

PINK1 Loss of Function Selectively Alters the Mitochondrial-Derived Vesicle Pathway.

Charlotte L Collier, Colleen Ruedi, Naomi J Thorne, David A Tumbarello.

Cell homeostasis and metabolic control require the efficient function of mitochondria and implementation of quality control pathways following damage. Cells have various discrete pathways of mitochondrial quality control (mitoQC) to maintain the healthy network. PINK1 and Parkin are two key players in mitoQC, most highly associated with the ubiquitin-dependent capture and degradation of whole mitochondria by autophagy. However, these proteins have alternative roles in repair routes directing locally damaged cargo to the lysosome, such as the mitochondrial-derived vesicle (MDV) pathway. We aimed to clarify the role of PINK1 and determine how its loss of function impacts mitochondrial dynamics and quality control. Results indicate PINK1 knockout (KO) has little impact on whole mitochondrial turnover in response to damage in SH-SY5Y cells, whereas both PINK1 and Parkin KO cells have healthy mitochondrial networks with efficient ATP production. However, TOM20 positive outer-membrane and damage-induced PDH-positive inner-membrane MDVs are elevated in PINK1 KO cells. Although, in contrast to Parkin KO, this is not due to a defect in trafficking to a LAMP1-positive compartment and may instead indicate increased damage-induced flux. In comparison, loss of Atg5-dependent mitophagy has no effect on whole mitochondrial turnover and only results in a limited elevation in inner-membrane MDVs in response to damage, indicating autophagy-independent mechanisms of whole mitochondrial turnover and a minor compensatory increase in damage-induced MDVs. Therefore, these data suggest PINK1 and Parkin are dispensable for whole mitochondrial turnover, but following their perturbation have disparate effects on the MDV pathway.

Keywords: Parkinson's; lysosome; membrane trafficking; mitochondria; mitochondrial quality control; vesicle transport

DOI: https://doi.org/10.1096/fba.2024-00200

Plant J. 2025 Jul;123(1): e70322

SGAM1 orchestrates salt tolerance by balancing mitochondrial translation and ROS homeostasis in Arabidopsis.

Jiangyan Dong, Zi-Ang Li, Xiao Yan, Fangfang Wang, Huchen Zhang, Guanting Niu, Hongjuan Chen, Zhi Hong.

Salt stress severely hampers plant growth and crop productivity. Defects in Golgi α1,2-mannosidase I MNS1 and MNS2 proteins, essential for N-glycan maturation, lead to severe root growth inhibition and swollen tips in Arabidopsis under salt stress. Here, we reported sgam1, a suppressor of mns1 mns2, exhibiting threshold-dependent suppression of salt sensitivity. SGAM1 encodes a mitochondria-localized pentatricopeptide repeat protein, and sgam1 mutations decreased the abundance and activity of mitochondrial electron transport complex (mETC), potentially by disrupting mitoribosome assembly and protein translation. This, in turn, alleviated the mitochondrial ROS accumulation and activated the AOX-mediated alternative respiratory pathway in mns1 mns2 under salt stress. Overexpression of AOX1a notably reversed the salt-sensitive root phenotype in mns1 mns2. Furthermore, sgam1 also suppressed other N-glycosylation mutants, suggesting a common mechanism. Our findings highlight the cooperative importance of N-glycosylation and mitochondrial activity in maintaining ROS homeostasis during salt stress.

Keywords: N‐glycosylation; PPR protein; mitochondria

DOI: https://doi.org/10.1111/tpj.70322