Lipid-dependent bimodal MCL1 membrane activity

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Mitochondrial lipid environment influences BCL2 family protein function.
• Mechanisms of MCL1 modulation by mitochondrial lipids are not well understood.

Purpose of the Study:

• Investigate how mitochondrial lipids affect MCL1 activity and conformation.
• Elucidate the role of specific lipids like cardiolipin and cholesterol.
• Identify key domains of MCL1 involved in membrane interactions.

Main Methods:

• Utilized minimalistic reconstituted membrane systems.
• Employed site-directed mutagenesis and fluorescence spectroscopy.
• Analyzed interactions with cBID and BAX, and effects of cardiolipin, phosphatidylinositol, and cholesterol.

Main Results:

• MCL1 inhibits membrane permeabilization via BH3-into-groove interactions, not requiring membrane embedding.
• Cardiolipin induces conformational changes in MCL1, leading to membrane integration and pore formation.
• Cholesterol reduces MCL1 conformational changes and pore activity in cardiolipin-rich membranes.
• MCL1α5 domain identified as crucial for membrane permeabilization.

Conclusions:

• Mitochondrial lipids actively regulate MCL1 function and conformation.
• MCL1 exhibits intrinsic lipidic pore-forming activity modulated by membrane composition.
• Findings provide novel mechanistic insights into MCL1's role in mitochondrial membrane dynamics.