Signal presequences increase mitochondrial permeability and open the multiple conductance channel

Area of Science:

• Mitochondrial biology
• Molecular and Cellular Biology
• Biophysics

Background:

• Signal presequences of mitochondrial proteins are known to interact with mitochondria.
• Previous work showed Neurospora crassa cytochrome oxidase subunit IV presequence increases mitochondrial permeability and regulates yeast inner mitochondrial membrane channels.

Purpose of the Study:

• To investigate the effects of various mitochondrial presequences and control peptides on mitochondrial permeability and multiple conductance channel (MCC) activity.
• To determine if specific peptide characteristics correlate with mitochondrial effects.

Main Methods:

• Utilized isolated rat liver mitochondria to assess peptide-induced permeability changes (swelling).
• Employed patch-clamp techniques on mammalian mitoplasts and reconstituted yeast systems to monitor MCC activity.
• Tested a range of mitochondrial presequences and control peptides.

Main Results:

• Most signal peptides, but not all, altered mitochondrial permeability.
• Positive charge and amphiphilic alpha-helix formation were insufficient to guarantee mitochondrial effects.
• A strong correlation was observed between peptide-induced mitochondrial swelling and MCC activation.
• Peptide efficacies were consistent across mitochondrial swelling and patch-clamp experiments.

Conclusions:

• Mitochondrial swelling and MCC activity changes induced by signal peptides likely reflect the opening of a single channel.
• This channel is selectively responsive to signal peptides and its opening depends on membrane potential.
• The identified channel is proposed to be involved in the mitochondrial protein import process.