Actin Cytoskeleton Regulates Calcium Dynamics and NFAT Nuclear Duration

Abstract

T-cell activation by antigen-presenting cells is accompanied by actin polymerization, T-cell receptor (TCR) capping, and formation of the immunological synapse. However, whether actin-dependent events are required for T-cell function is poorly understood. Herein, we provide evidence for an unexpected negative regulatory role of the actin cytoskeleton on TCR-induced cytokine production. Disruption of actin polymerization resulted in prolonged intracellular calcium elevation in response to anti-CD3, thapsigargin, or phorbol myristate acetate plus ionomycin, leading to persistent NFAT (nuclear factor of activated T cells) nuclear duration. These events were dominant, as the net effect of actin blockade was augmented interleukin 2 promoter activity. Increased surface expression of the plasma membrane Ca²⁺ ATPase was observed upon stimulation, which was inhibited by cytochalasin D, suggesting that actin polymerization contributes to calcium export. Our results imply a novel role for the actin cytoskeleton in modulating the duration of Ca²⁺-NFAT signaling and indicate that actin dynamics regulate features of T-cell activation downstream of receptor clustering.

We are grateful to J. Miller, A. Sperling, A. Lin, and M. Peter for providing mice and reagents, and we thank B. Eisfelder, V. Bindokas, P. E. Fields, and H. Harlin for experimental advice. We also thank J. Washington and E. Marshall for technical assistance.

This work was supported by NIH grant number R01 AI47919.