Mitochondrial preservation through the PKA-DRP1 axis empowers natural killer cells to resist acidic stress and retain cytotoxicity.

BACKGROUND

Natural killer (NK) cells are critical components with potent cytotoxic capabilities in immunosurveillance against cancer. However, their function is often impaired in the acidic tumor microenvironment due to mitochondrial dysfunction.

METHODS

Chemically primed NK (Chem_NK) cells were generated with 25 kDa branched polyethylenimine. Cytotoxicity and motility assays were performed at physiological (pH 7.5) and acidic (pH 6.0) conditions. Building upon our previous proteomic profiling, which identified metabolic reprogramming in Chem_NK cells, we here investigated the functional consequences of these changes under environmental stress, and pharmacological inhibition studies were used to validate the role of oxidative phosphorylation (OXPHOS).

RESULTS

Chem_NK cells treated with 25 kDa branched polyethylenimine maintain superior cytotoxicity and motility under acidic conditions. Proteomic and metabolic analyses revealed that OXPHOS was elevated in Chem_NK cells, which supported sustained mitochondrial ATP production and respiratory capacity at pH 6.0. Inhibition of OXPHOS abolished these advantages, confirming that mitochondrial respiration is essential for acid resistance. Mechanistically, Chem_NK cells preserve mitochondrial integrity through the protein kinase A (PKA)–dynamin-related protein 1 (DRP1) axis. Under acidic stress, DRP1 phosphorylation at Ser616 (S616) was reduced, while increased PKA activity elevated phosphorylation at Ser637 (S637), suppressing mitochondrial fragmentation.

CONCLUSIONS

These findings highlight mitochondrial preservation via the PKA–DRP1 axis as a key mechanism underlying NK cell function under acidic stress and suggest a potential strategy to enhance NK cell-based immunotherapy in solid tumors.