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- Vázquez Calvo, Carmela, 1983-
(author)
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Interconnectivity of mitochondrial protein biogenesis and homeostasis
- 2023
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Doctoral thesis (other academic/artistic)abstract
- To ensure correct protein function, the cells are equipped with a tightly regulated network of chaperones that support protein folding and actively participate in protein quality control (PQC) and turnover. Due to the dual origin of the mitochondrial proteome, the cytosolic and mitochondrial PQC networks coordinate to ensure protein import and assembly in the organelle. In particular, chaperones play crucial roles during protein synthesis and de novo folding, but also during protein import and insertion into membranes. Despite the increasing knowledge on the involvement of the cytosolic chaperone networks on surveilling mitochondrial proteins prior and during import, many aspects of the function of the mitochondrial PQC systems are still enigmatic.In this thesis I focused on shedding light on the molecular mechanisms underlying protein aggregate handling and chaperone-dependent folding capacity in mitochondria as well as understanding the effect of metals on mitochondrial protein stability and the dual origin of some mitochondrial proteins. Paper I, studies the relevance of the metabolic status of the cells in protein aggregate handling and identifies newly synthetized proteins as the main source of aggregates. In line with this, in Paper II we have developed a novel reporter that allows us to study the capacity of the folding chaperones in vivo under acute or chronic stress. Paper III, analyses the effects of Mn2+ overdose on protein stability and its implications in mitochondrial homeostasis and Paper IV, explores the dual origin of the novel component of the α-ketoglutarate dehydrogenase complex, Kgd4.
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| 2. |
- Vazquez-Calvo, Carmela, 1983-, et al.
(author)
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Newly imported proteins in mitochondria are particularly sensitive to aggregation
- 2023
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In: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 238:3
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Journal article (peer-reviewed)abstract
- Aim: A functional proteome is essential for life and maintained by protein quality control (PQC) systems in the cytosol and organelles. Protein aggregation is an indicator of a decline of PQC linked to aging and disease. Mitochondrial PQC is critical to maintain mitochondrial function and thus cellular fitness. How mitochondria handle aggregated proteins is not well understood. Here we tested how the metabolic status impacts on formation and clearance of aggregates within yeast mitochondria and assessed which proteins are particularly sensitive to denaturation.Methods: Confocal microscopy, electron microscopy, immunoblotting and genetics were applied to assess mitochondrial aggregate handling in response to heat shock and ethanol using the mitochondrial disaggregase Hsp78 as a marker for protein aggregates.Results: We show that aggregates formed upon heat or ethanol stress with different dynamics depending on the metabolic state. While fermenting cells displayed numerous small aggregates that coalesced into one large foci that was resistant to clearance, respiring cells showed less aggregates and cleared these aggregates more efficiently. Acute inhibition of mitochondrial translation had no effect, while preventing protein import into mitochondria by inhibition of cytosolic translation prevented aggregate formation.Conclusion: Collectively, our data show that the metabolic state of the cells impacts the dynamics of aggregate formation and clearance, and that mainly newly imported and not yet assembled proteins are prone to form aggregates. Because mitochondrial functionality is crucial for cellular metabolism, these results highlight the importance of efficient protein biogenesis to maintain the mitochondrial proteome operational during metabolic adaptations and cellular stress.
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