scholarly journals Mitochondrial Lon protease is a gatekeeper for proteins newly imported into the matrix

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuichi Matsushima ◽  
Kazuya Takahashi ◽  
Song Yue ◽  
Yuki Fujiyoshi ◽  
Hideaki Yoshioka ◽  
...  
Keyword(s):  
Protease Activity ◽  
Matrix Protein ◽  
Protein Import ◽  
Atp Hydrolysis ◽  
Lon Protease ◽  
Mitochondrial Matrix ◽  
The Matrix ◽  
Specific Proteins ◽  
Aggregation Activity ◽  
Hydrolysis Activity

AbstractHuman ATP-dependent Lon protease (LONP1) forms homohexameric, ring-shaped complexes. Depletion of LONP1 causes aggregation of a broad range of proteins in the mitochondrial matrix and decreases the levels of their soluble forms. The ATP hydrolysis activity, but not protease activity, of LONP1 is critical for its chaperone-like anti-aggregation activity. LONP1 forms a complex with the import machinery and an incoming protein, and protein aggregation is linked with matrix protein import. LONP1 also contributes to the degradation of imported, aberrant, unprocessed proteins using its protease activity. Taken together, our results show that LONP1 functions as a gatekeeper for specific proteins imported into the mitochondrial matrix.

scholarly journals Characterization of Mmp37p, aSaccharomyces cerevisiaeMitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

2006 ◽  
Vol 17 (9) ◽  
pp. 4051-4062 ◽  
Author(s):  
Michelle R. Gallas ◽  
Mary K. Dienhart ◽  
Rosemary A. Stuart ◽  
Roy M. Long
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Close Proximity ◽  
The Matrix ◽  
Targeting Signal

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix.

scholarly journals A Mechanistic Perspective on PEX1 and PEX6, Two AAA+ Proteins of the Peroxisomal Protein Import Machinery

2019 ◽  
Vol 20 (21) ◽  
pp. 5246 ◽  
Author(s):  
Ana G. Pedrosa ◽  
Tânia Francisco ◽  
Maria J. Ferreira ◽  
Tony A. Rodrigues ◽  
Aurora Barros-Barbosa ◽  
...  
Keyword(s):  
Self Assembly ◽  
Driving Force ◽  
Matrix Protein ◽  
Protein Import ◽  
Atp Hydrolysis ◽  
Transport Proteins ◽  
Gtp Hydrolysis ◽  
Assembly Mechanism ◽  
Dependent Protein ◽  
Organelle Membrane

In contrast to many protein translocases that use ATP or GTP hydrolysis as the driving force to transport proteins across biological membranes, the peroxisomal matrix protein import machinery relies on a regulated self-assembly mechanism for this purpose and uses ATP hydrolysis only to reset its components. The ATP-dependent protein complex in charge of resetting this machinery—the Receptor Export Module (REM)—comprises two members of the “ATPases Associated with diverse cellular Activities” (AAA+) family, PEX1 and PEX6, and a membrane protein that anchors the ATPases to the organelle membrane. In recent years, a large amount of data on the structure/function of the REM complex has become available. Here, we discuss the main findings and their mechanistic implications.

scholarly journals Lon protease: a novel mitochondrial matrix protein in the interconnection between drug-induced mitochondrial dysfunction and endoplasmic reticulum stress

2017 ◽  
Vol 174 (23) ◽  
pp. 4409-4429 ◽  
Author(s):  
Miriam Polo ◽  
Fernando Alegre ◽  
Angela B Moragrega ◽  
Lara Gibellini ◽  
Alberto Marti-Rodrigo ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Mitochondrial Dysfunction ◽  
Matrix Protein ◽  
Lon Protease ◽  
Mitochondrial Matrix ◽  
Drug Induced

scholarly journals The unique degradation pathway of the PTS2 receptor, Pex7, is dependent on the PTS receptor/coreceptor, Pex5 and Pex20

2014 ◽  
Vol 25 (17) ◽  
pp. 2634-2643 ◽  
Author(s):  
Danielle Hagstrom ◽  
Changle Ma ◽  
Soumi Guha-Polley ◽  
Suresh Subramani
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Degradation Pathway ◽  
Matrix Proteins ◽  
Receptor Recycling ◽  
Wild Type ◽  
The Matrix ◽  
Peroxisomal Targeting ◽  
Targeting Signals ◽  
The Stability

Peroxisomal matrix protein import uses two peroxisomal targeting signals (PTSs). Most matrix proteins use the PTS1 pathway and its cargo receptor, Pex5. The PTS2 pathway is dependent on another receptor, Pex7, and its coreceptor, Pex20. We found that during the matrix protein import cycle, the stability and dynamics of Pex7 differ from those of Pex5 and Pex20. In Pichia pastoris, unlike Pex5 and Pex20, Pex7 is constitutively degraded in wild-type cells but is stabilized in pex mutants affecting matrix protein import. Degradation of Pex7 is more prevalent in cells grown in methanol, in which the PTS2 pathway is nonessential, in comparison with oleate, suggesting regulation of Pex7 turnover. Pex7 must shuttle into and out of peroxisomes before it is polyubiquitinated and degraded by the proteasome. The shuttling of Pex7, and consequently its degradation, is dependent on the receptor recycling pathways of Pex5 and Pex20 and relies on an interaction between Pex7 and Pex20. We also found that blocking the export of Pex20 from peroxisomes inhibits PTS1-mediated import, suggesting sharing of limited components in the export of PTS receptors/coreceptors. The shuttling and stability of Pex7 are divergent from those of Pex5 and Pex20, exemplifying a novel interdependence of the PTS1 and PTS2 pathways.

scholarly journals Role of the mitochondrial DnaJ homolog Mdj1p as a chaperone for mitochondrially synthesized and imported proteins.

1996 ◽  
Vol 16 (12) ◽  
pp. 7063-7071 ◽  
Author(s):  
B Westermann ◽  
B Gaume ◽  
J M Herrmann ◽  
W Neupert ◽  
E Schwarz
Keyword(s):  
Protein Import ◽  
Firefly Luciferase ◽  
Mitochondrial Matrix ◽  
Mitochondrial Ribosomes ◽  
The Matrix ◽  
Mitochondrial Hsp70 ◽  
In Transit ◽  
Polypeptide Chains ◽  
Induced Aggregation

Mdj1p, a DnaJ homolog in the mitochondria of Saccharomyces cerevisiae, is involved in the folding of proteins in the mitochondrial matrix. In this capacity, Mdj1p cooperates with mitochondrial Hsp70 (mt-Hsp70). Here, we analyzed the role of Mdj1p as a chaperone for newly synthesized proteins encoded by mitochondrial DNA and for nucleus-encoded proteins as they enter the mitochondrial matrix. A series of conditional mutants of mdj1 was constructed. Mutations in the various functional domains led to a partial loss of Mdj1p function. The mutant Mdj1 proteins were defective in protecting the tester protein firefly luciferase against heat-induced aggregation in isolated mitochondria. The mitochondrially encoded var1 protein showed enhanced aggregation after synthesis in mdj1 mutant mitochondria. Mdj1p and mt-Hsp70 were found in a complex with nascent polypeptide chains on mitochondrial ribosomes. Mdj1p was not found to interact with translocation intermediates of imported proteins spanning the two membranes and exposing short segments into the matrix, in accordance with the lack of requirement of Mdj1p in the mt-Hsp70-mediated protein import into mitochondria. On the other hand, precursor proteins in transit which had further entered the matrix were found in a complex with Mdj1p. Our results suggest that Mdj1p together with mt-Hsp70 plays an important role as a chaperone for mitochondrially synthesized polypeptide chains emerging from the ribosome and for translocating proteins at a late import step.

The Matrix Protein Import Complex in Yeast

2014 ◽  
pp. 305-323 ◽  
Author(s):  
Daniel Effelsberg ◽  
Ralf Erdmann ◽  
Wolfgang Schliebs
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
The Matrix

Tom20-mediated mitochondrial protein import in muscle cells during differentiation

2000 ◽  
Vol 279 (5) ◽  
pp. C1393-C1400 ◽  
Author(s):  
Janice Y. Grey ◽  
Michael K. Connor ◽  
Joseph W. Gordon ◽  
Masato Yano ◽  
Masataka Mori ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Muscle Cells ◽  
In Vitro Assays ◽  
Organelle Biogenesis ◽  
Outer Membrane Receptor ◽  
The Matrix

Mitochondrial biogenesis is accompanied by an increased expression of components of the protein import machinery, as well as increased import of proteins destined for the matrix. We evaluated the role of the outer membrane receptor Tom20 by varying its expression and measuring changes in the import of malate dehydrogenase (MDH) in differentiating C2C12 muscle cells. Cells transfected with Tom20 had levels that were twofold higher than in control cells. Labeling of cells followed by immunoprecipitation of MDH revealed equivalent increases in MDH import. This parallelism between import rate and Tom20 levels was also evident as a result of thyroid hormone treatment. Using antisense oligodeoxynucleotides, we inhibited Tom20 expression by 40%, resulting in 40–60% reductions in MDH import. In vitro assays also revealed that import into the matrix was more sensitive to Tom20 inhibition than import into the outer membrane. These data indicate a close relationship between induced changes in Tom20 and the import of a matrix protein, suggesting that Tom20 is involved in determining the kinetics of import. However, this relationship was dissociated during normal differentiation, since the expression of Tom20 remained relatively constant, whereas imported MDH increased 12-fold. Thus Tom20 is important in determining import during organelle biogenesis, but other mechanisms (e.g., intramitochondrial protein degradation or nuclear transcription) likely also play a role in establishing the final mitochondrial phenotype during normal muscle differentiation.

scholarly journals The mitochondrial intermembrane space: the most constricted mitochondrial sub-compartment with the largest variety of protein import pathways

Open Biology ◽  
2021 ◽  
Vol 11 (3) ◽  
Author(s):  
Ruairidh Edwards ◽  
Ross Eaglesfield ◽  
Kostas Tokatlidis
Keyword(s):  
Protein Import ◽  
Atp Hydrolysis ◽  
Current Knowledge ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Mitochondrial Proteome ◽  
Normal Site ◽  
The Matrix ◽  
Human Disorders ◽  
Mitochondrial Intermembrane Space

The mitochondrial intermembrane space (IMS) is the most constricted sub-mitochondrial compartment, housing only about 5% of the mitochondrial proteome, and yet is endowed with the largest variability of protein import mechanisms. In this review, we summarize our current knowledge of the major IMS import pathway based on the oxidative protein folding pathway and discuss the stunning variability of other IMS protein import pathways. As IMS-localized proteins only have to cross the outer mitochondrial membrane, they do not require energy sources like ATP hydrolysis in the mitochondrial matrix or the inner membrane electrochemical potential which are critical for import into the matrix or insertion into the inner membrane. We also explore several atypical IMS import pathways that are still not very well understood and are guided by poorly defined or completely unknown targeting peptides. Importantly, many of the IMS proteins are linked to several human diseases, and it is therefore crucial to understand how they reach their normal site of function in the IMS. In the final part of this review, we discuss current understanding of how such IMS protein underpin a large spectrum of human disorders.

ATP-driven processes of peroxisomal matrix protein import

2017 ◽  
Vol 398 (5-6) ◽  
pp. 607-624 ◽  
Author(s):  
Daniel P. Schwerter ◽  
Immanuel Grimm ◽  
Harald W. Platta ◽  
Ralf Erdmann
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Atp Hydrolysis ◽  
Current Knowledge ◽  
Model Organism ◽  
Peroxisomal Membrane ◽  
Dual Localization ◽  
Import Receptors ◽  
Membrane Bound ◽  
Atp Binding And Hydrolysis

Abstract In peroxisomal matrix protein import two processes directly depend on the binding and hydrolysis of ATP, both taking place at the late steps of the peroxisomal import cycle. First, ATP hydrolysis is required to initiate a ubiquitin-transfer cascade to modify the import (co-)receptors. These receptors display a dual localization in the cytosol and at the peroxisomal membrane, whereas only the membrane bound fraction receives the ubiquitin modification. The second ATP-dependent process of the import cycle is carried out by the two AAA+-proteins Pex1p and Pex6p. These ATPases form a heterohexameric complex, which is recruited to the peroxisomal import machinery by the membrane anchor protein Pex15p. The Pex1p/Pex6p complex recognizes the ubiquitinated import receptors, pulls them out of the membrane and releases them into the cytosol. There the deubiquitinated receptors are provided for further rounds of import. ATP binding and hydrolysis are required for Pex1p/Pex6p complex formation and receptor export. In this review, we summarize the current knowledge on the peroxisomal import cascade. In particular, we will focus on the ATP-dependent processes, which are so far best understood in the model organism Saccharomyces cerevisiae.

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.

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