Characterization of the functional properties of the voltage-gated potassium channel Kv1.3 in human CD4⁺ T lymphocytes

Previous studies have shown that central memory T (T_CM) cells predominantly use the calcium-dependent potassium channel KCa3.1 during acute activation, whereas effector memory T (T_EM) cells use the voltage-gated potassium channel Kv1.3. Because Kv1.3-specific pharmacological blockade selectively inhibited anti-CD3-mediated proliferation, whereas naive T cells and T_CM cells escaped inhibition due to up-regulation of KCa3.1, this difference indicated a potential for selective targeting of the T_EM population. We examined the effects of pharmacological Kv1.3 blockers and a dominant-negative Kv1.x construct on T cell subsets to assess the specific effects of Kv1.3 blockade. Our studies indicated both T_CM and T_EM CD4⁺ T cells stimulated with anti-CD3 were inhibited by charybdotoxin, which can block both KCa3.1 and Kv1.3, whereas margatoxin and Stichodactyla helianthus toxin, which are more selective Kv1.3 inhibitors, inhibited proliferation and IFN-γ production only in the T_EM subset. The addition of anti-CD28 enhanced proliferation of freshly isolated cells and rendered them refractory to S. helianthus, whereas chronically activated T_EM cell lines appeared to be costimulation independent because Kv1.3 blockers effectively inhibited proliferation and IFN-γ regardless of second signal. Transduction of CD4⁺ T cells with dominant-negative Kv1.x led to a higher expression of CCR7⁺ T_CM phenotype and a corresponding depletion of T_EM. These data provide further support for Kv1.3 as a selective target of chronically activated T_EM without compromising naive or T_CM immune functions. Specific Kv1.3 blockers may be beneficial in autoimmune diseases such as multiple sclerosis in which T_EM are found in the target organ.