Intracellular K+ Limits T-cell Exhaustion and Preserves Antitumor Function

Area of Science:

• Immunology
• Cellular Biology
• Cancer Research

Background:

• T cell function is often impaired in the tumor microenvironment.
• Elevated extracellular potassium (K+) in tumors can suppress CD8+ T cell signaling and effector functions.
• The Na+/K+ ATPase (encoded by Atp1a1) is a key transporter regulating intracellular K+ in T cells.

Purpose of the Study:

• To investigate the impact of genetically reducing intracellular K+ on CD8+ T cell function and exhaustion.
• To explore strategies for mitigating K+-mediated T cell dysfunction in cancer.

Main Methods:

• CRISPR-Cas9 gene editing to disrupt the Atp1a1 locus in CD8+ T cells.
• Measurement of intracellular K+ levels, membrane potential (Vm), Ca2+ influx, and signaling pathway activity.
• Assessment of T cell exhaustion markers, reactive oxygen species (ROS) production, and antioxidant effects.
• Evaluation of T cell persistence and anti-tumor activity in a murine melanoma model.

Main Results:

• Disruption of Atp1a1 lowered intracellular K+ and increased membrane potential, despite reduced Ca2+ influx.
• Atp1a1-deficient T cells exhibited tonic signaling hyperactivity and a phenotype of exhaustion in both mouse and human cells.
• Exogenous K+ or antioxidant treatment prevented ROS accumulation and T cell exhaustion in vitro.
• Atp1a1-deficient T cells showed impaired persistence and anti-tumor efficacy in vivo.

Conclusions:

• Genetic reduction of intracellular K+ in CD8+ T cells leads to complex functional alterations, including exhaustion.
• Strategies involving K+ repletion or antioxidant treatment can ameliorate T cell dysfunction and restore anti-tumor activity.
• Balancing intracellular K+ levels is crucial for optimizing T cell effector function in cancer immunotherapy.