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Related Concept Videos

Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
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Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
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Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

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Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
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Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

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Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
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Energy to Drive Translocation01:37

Energy to Drive Translocation

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Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
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Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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How does protein degradation regulate TOM machinery-dependent mitochondrial import?

Mohamed A Eldeeb1,2, Mohamed A Ragheb3, Mansoore Esmaili4

  • 1Chemistry Department (Biochemistry Division), Faculty of Science, Cairo University, Giza, Egypt. Eldeeb@ualberta.ca.

Current Genetics
|February 16, 2020
PubMed
Summary

Mitochondrial dysfunction is key in aging. Proteasomal degradation fine-tunes mitochondrial import, offering potential therapeutic targets for neurodegenerative diseases.

Keywords:
Mitochondrial importMitochondrial quality controlMitophagyProteasomeProtein degradationProtein quality controlTOM complexUbiquitin

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Area of Science:

  • Cell Biology
  • Molecular Biology
  • Aging Research

Background:

  • Mitochondrial dysregulation is a hallmark of aging and age-related diseases.
  • Understanding the mechanisms linking protein aggregation and mitochondrial import failure is crucial.
  • The role of the proteasome in mitochondrial quality control is an emerging area of research.

Purpose of the Study:

  • To analyze the role of proteasomal-mediated degradation in regulating the fidelity of TOM machinery-dependent mitochondrial import.
  • To explore the connection between abnormal mitochondrial precursor protein fragments and impaired mitochondrial import.
  • To discuss potential applications of these findings in neurodegenerative disorder therapies.

Main Methods:

  • Literature review and analysis of existing data on proteasomal degradation and mitochondrial import.
  • Discussion of the TOM (Translocase of the Outer Mitochondrial membrane) machinery.
  • Analysis of molecular mechanisms underlying mitochondrial protein import regulation.

Main Results:

  • Proteasomal-dependent degradation acts as a key regulator of mitochondrial protein import via the TOM machinery.
  • This process is critical for maintaining the fidelity of mitochondrial import.
  • Dysfunction in this pathway may contribute to the pathogenesis of aging-related disorders.

Conclusions:

  • Proteasomal degradation plays a vital role in ensuring accurate mitochondrial import.
  • Targeting proteasomal regulation of mitochondrial import may offer novel therapeutic strategies for neurodegenerative diseases.
  • Further research into this pathway could elucidate mechanisms underlying aging and disease.