scholarly journals Increased levels of the mitochondrial import factor Mia40 prevent the aggregation of polyQ proteins in the cytosol

2021 ◽  
Author(s):  
Anna M. Schlagowski ◽  
Katharina Knöringer ◽  
Sandrine Morlot ◽  
Ana Sáchez Vicente ◽  
Felix Boos ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Model System ◽  
Model Systems ◽  
Aggregate Formation ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Polyq Protein ◽  
Rate Limiting

AbstractThe formation of protein aggregates is a hallmark of neurodegenerative diseases. Observations on patient material and model systems demonstrated links between aggregate formation and declining mitochondrial functionality, but the causalities remained unclear. We used yeast as model system to analyze the relevance of mitochondrial processes for the behavior of an aggregation-prone polyQ protein derived from human huntingtin. Induction of Q97-GFP rapidly leads to insoluble cytosolic aggregates and cell death. Although this aggregation impairs mitochondrial respiration only slightly, it interferes with efficient import of mitochondrial precursor proteins. Mutants in the import component Mia40 are hypersensitive to Q97-GFP. Even more surprisingly, Mia40 overexpression strongly suppresses the formation of toxic Q97-GFP aggregates both in yeast and in human cells. Based on these observations, we propose that the posttranslational import into mitochondria competes with aggregation-prone cytosolic proteins for chaperones and proteasome capacity. Owing to its rate-limiting role for mitochondrial protein import, Mia40 acts as a regulatory component in this competition. This role of Mia40 as dynamic regulator in mitochondrial biogenesis can apparently be exploited to stabilize cytosolic proteostasis. (174/175 words)

scholarly journals Reinvestigation of the Requirement of Cytosolic ATP for Mitochondrial Protein Import

2004 ◽  
Vol 279 (19) ◽  
pp. 19464-19470 ◽  
Author(s):  
Takeyoshi Asai ◽  
Takashi Takahashi ◽  
Masatoshi Esaki ◽  
Shuh-ichi Nishikawa ◽  
Kenzo Ohtsuka ◽  
...  
Keyword(s):  
Protein Import ◽  
Atp Hydrolysis ◽  
Mitochondrial Protein ◽  
Mitochondrial Matrix ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Reticulocyte Lysate ◽  
Binding To Mitochondria

Protein import into mitochondria requires the energy of ATP hydrolysis inside and/or outside mitochondria. Although the role of ATP in the mitochondrial matrix in mitochondrial protein import has been extensively studied, the role of ATP outside mitochondria (external ATP) remains only poorly characterized. Here we developed a protocol for depletion of external ATP without significantly reducing the import competence of precursor proteins synthesizedin vitrowith reticulocyte lysate. We tested the effects of external ATP on the import of various precursor proteins into isolated yeast mitochondria. We found that external ATP is required for maintenance of the import competence of mitochondrial precursor proteins but that, once they bind to mitochondria, the subsequent translocation of presequence-containing proteins, but not the ADP/ATP carrier, proceeds independently of external ATP. Because depletion of cytosolic Hsp70 led to a decrease in the import competence of mitochondrial precursor proteins, external ATP is likely utilized by cytosolic Hsp70. In contrast, the ADP/ATP carrier requires external ATP for efficient import into mitochondria even after binding to mitochondria, a situation that is only partly attributed to cytosolic Hsp70.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

scholarly journals Inactivation of the Neurospora crassa gene encoding the mitochondrial protein import receptor MOM19 by the technique of "sheltered RIP".

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 107-118 ◽  
Author(s):  
T A Harkness ◽  
R L Metzenberg ◽  
H Schneider ◽  
R Lill ◽  
W Neupert ◽  
...  
Keyword(s):  
Neurospora Crassa ◽  
Target Gene ◽  
Protein Import ◽  
Selectable Marker ◽  
Mitochondrial Protein ◽  
Mutant Gene ◽  
Mitochondrial Protein Import ◽  
Gene Encoding ◽  
Precursor Proteins ◽  
Import Receptor

Abstract We have used a technique referred to as "sheltered RIP" (repeat induced point mutation) to create mutants of the mom-19 gene of Neurospora crassa, which encodes an import receptor for nuclear encoded mitochondrial precursor proteins. Sheltered RIP permits the isolation of a mutant gene in one nucleus, even if that gene is essential for the survival of the organism, by sheltering the nucleus carrying the mutant gene in a heterokaryon with an unaffected nucleus. Furthermore, the nucleus harboring the RIPed gene contains a selectable marker so that it is possible to shift nuclear ratios in the heterokaryons to a state in which the nucleus containing the RIPed gene predominates in cultures grown under selective conditions. This results in a condition where the target gene product should be present at very suboptimal levels and allows the study of the mutant phenotype. One allele of mom-19 generated by this method contains 44 transitions resulting in 18 amino acid substitutions. When the heterokaryon containing this allele was grown under conditions favoring the RIPed nucleus, no MOM19 protein was detectable in the mitochondria of the strain. Homokaryotic strains containing the RIPed allele exhibit a complex and extremely slow growth phenotype suggesting that the product of the mom-19 gene is important in N. crassa.

scholarly journals A chimeric mitochondrial precursor protein with internal disulfide bridges blocks import of authentic precursors into mitochondria and allows quantitation of import sites.

1988 ◽  
Vol 107 (6) ◽  
pp. 2037-2043 ◽  
Author(s):  
D Vestweber ◽  
G Schatz
Keyword(s):  
Trypsin Inhibitor ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Precursor Protein ◽  
Disulfide Bridges ◽  
Mitochondrial Protein Import ◽  
Mitochondrial Inner Membrane ◽  
Precursor Proteins ◽  
The Matrix ◽  
Pancreatic Trypsin Inhibitor

Bovine pancreatic trypsin inhibitor (which contains three intramolecular disulfide bridges) was chemically coupled to the COOH terminus of a purified artificial mitochondrial precursor protein. When the resulting chimeric precursor was presented to energized isolated yeast mitochondria, its trypsin inhibitor moiety prevented the protein from completely entering the organelle; the protein remained stuck across both mitochondrial membranes, with its NH2 terminus in the matrix and its trypsin inhibitor moiety still exposed on the mitochondrial surface. The incompletely imported protein appeared to "jam" mitochondrial protein import sites since it blocked import of three authentic mitochondrial precursor proteins; it did not collapse the potential across the mitochondrial inner membrane. Quantification of the inhibition indicated that each isolated mitochondrial particle contains between 10(2) and 10(3) protein import sites.

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