Massive endocytosis triggered by surface membrane palmitoylation under mitochondrial control in BHK fibroblasts

Area of Science:

• Cell Biology
• Mitochondrial Biology
• Membrane Trafficking

Background:

• Large calcium (Ca) transients induce massive endocytosis (MEND) in BHK fibroblasts through nonclassical pathways.
• The precise molecular mechanisms linking Ca transients to MEND remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying calcium-induced massive endocytosis (MEND).
• To investigate the role of mitochondrial signaling in regulating MEND and plasmalemma turnover.

Main Methods:

• Utilized pharmacological inhibitors targeting mitochondrial function, coenzyme A metabolism, and protein palmitoylation.
• Employed siRNA to knockdown specific acyl transferases (DHHC5).
• Investigated the effects of mitochondrial depolarization, oxidative stress, and PKC activation on MEND.

Main Results:

• MEND is dependent on mitochondrial permeability transition pore (PTP) openings, coenzyme A (CoA) release, acyl CoA synthesis, and membrane protein palmitoylation.
• Inhibition of these steps or depletion of fatty acids blocks MEND, while restoration with acyl CoA or CoA rescues the process.
• Knockdown of DHHC5 inhibits MEND, and transient oxidative stress or PKC activation initiates MEND when acyl CoA is abundant.
• Mitochondrial PTP inhibition increases plasmalemma in normally growing cells.

Conclusions:

• MEND is a novel pathway regulated by mitochondrial stress signaling, involving PTP opening, CoA metabolism, and DHHC5-mediated palmitoylation.
• This pathway contributes to both constitutive and pathological plasmalemma turnover.
• Mitochondrial dysfunction and associated signaling represent a potential therapeutic target for conditions involving aberrant membrane trafficking.