Cytosolic Acidification Is the First Transduction Signal of Lactoferrin-induced Regulated Cell Death Pathway

Area of Science:

• Cell Biology
• Biochemistry
• Ion Transport

Background:

• Regulated cell death (RCD) is a crucial biological process.
• Human lactoferrin (hLf) is an antimicrobial protein involved in innate immunity.
• Previous studies implicated K+ efflux in hLf-induced RCD in yeast.

Purpose of the Study:

• To identify the specific K+ channel responsible for K+ efflux during hLf-induced RCD in yeast.
• To elucidate the ionic signaling pathway initiating hLf-induced RCD.
• To investigate the role of cytosolic pH changes in RCD.

Main Methods:

• Utilized yeast strains with disrupted TOK1 gene.
• Applied K+ channel blockers and varied extracellular K+ concentrations.
• Measured cytosolic pH changes in hLf-treated cells.
• Investigated the effects of ionophores like valinomycin, NH4Cl, and nigericin.

Main Results:

• The K+ channel Tok1p was identified as the primary mediator of K+ efflux.
• Disruption of TOK1 conferred resistance to hLf.
• K+ depletion alone was insufficient to induce RCD.
• Transient cytosolic acidification was necessary and sufficient to trigger RCD.
• hLf-induced Pma1p H+-ATPase inhibition led to cytosolic acidification and membrane depolarization, activating Tok1p.

Conclusions:

• Tok1p-mediated K+ efflux and cytosolic acidification are critical initiating signals in hLf-induced RCD.
• The study reveals a novel ionic signaling pathway in mitochondria-mediated cell death.
• These findings provide new insights into the mechanisms of antimicrobial protein-induced cell death.